Air filtration equipment comprising a filter leakage detection function

Abstract

Air filtration equipment (100, 900) comprising a body (101) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor 5 arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, where detection of filter leakage by the control unit (150) is conditioned on that a start- up time period (510) has passed from activation of the air filtration equipment (100, 900).

Description

[0001] AIR FILTRATION EQUIPMENT COMPRISING A FILTER LEAKAGE DETECTION

[0002] FUNCTION

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to air filtration equipment such as air cleaners for use on construction sites and in other environments where it is desired to remove particulate matter from the ambient air and heavy-duty dust extractors designed to filter out dust and debris from a suction air flow. The air cleaners discussed herein are active air cleaners which filter the ambient air by means of a fan and filter arrangement in order to capture particulate matter and / or unwanted gas in the surrounding environment. The dust extractors discussed herein comprise cyclone tanks designed to separate out coarse dust from the suction air flow, followed by one or more air filters configured to capture smaller dust particles.

[0005] BACKGROUND

[0006] Construction work such as concrete processing operations often involve processes that generate dust which can be harmful to personnel at the construction site. Construction site work tasks may also involve coating operations, such as painting and spraying, which release harmful gaseous matter into the ambient air.

[0007] An air cleaner can be used to filter the ambient air at a construction site in order to remove harmful particles and gas from the air.

[0008] It is important that the air cleaners deployed at a construction work site are fully functional such that the ambient air at the work site is efficiently filtered.

[0009] The dust generated by the concrete processing operations can be efficiently collected by a dust extractor, accumulated in a dust container of the dust extractor, and removed from the construction site in a controlled manner. Dust extractors are heavy- duty vacuum devices which collect dust and slurry by generating an under-pressure in a cyclone tank by means of a fan. This allows the dust extractor to collect larger quantities of dust compared to domestic vacuum cleaners which normally lack a cyclone tank. Some dust extractors comprise a coarse prefilter arranged inside the cyclone tank, followed by a finer filter downstream of the prefilter, such as a high- efficiency particulate air (HEPA) filter. SUMMARY

[0010] It is an objective of the present disclosure to provide improved air filtration equipment, in particular air cleaners and heavy-duty dust extractors, comprising automatic filter leakage detection functions.

[0011] This objective may at least in part be obtained by air filtration equipment comprising a body arranged to support one or more air filters. The air filtration equipment comprises a fan arranged to generate an air flow through the one or more air filters, a particle sensor arrangement arranged downstream from the one or more air filters in order to evaluate a particle concentration in the filtered air flow, and a control unit arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement. The particle sensor arrangement is preferably arranged downstream from the fan, but it can also be positioned upstream from the fan. The control unit is configured to detect leakage in at least one air filter out of the one or more air filters in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, such as exceedance of a predetermined particle concentration threshold or a more advanced statistical detection criteria. The acceptance criterion may comprise different allowed particle concentration values for different particle sizes. Two or more particle sensors can also be used, e.g., in case it is desired to identify which filter that has a leak, or to verify that a filter is intact, i.e., not leaking. Detection of filter leakage by the control unit is conditioned on that a start-up time period has passed from activation of the air filtration equipment. This means that the air filtration equipment is operated for a given time period before the control unit tries to detect filter leakage. Initially operating the air filtration equipment during the start-up time period cleans out any residual dust from previous air filtration operations, dust accumulated during storage of the air filtration equipment, and also dust accumulated in the equipment during transport to the work site. Thus, a more reliable filter leakage detection function is obtained. The start-up time period is in some cases at least 30 seconds, and preferably at least 1 minute, and more preferably at least 5 minutes, such as about 8 minutes.

[0012] The air filtration equipment may comprise an air cleaner arranged to filter ambient air at a work site or a heavy-duty dust extractor arranged to filter air in a particle laden suction air flow, such as a suction air flow from dust generating concrete processing equipment. At least some of the air filtration equipment discussed herein are air cleaners that are configurable in a fan mode of operation, which is a mode of operation where air is only moved at the work site and not filtered. The air filters are normally removed from an air cleaner when operating in the fan mode of operation. The control unit can be configured to suspend detection of air filter leakage when the air cleaner operates in the fan mode of operation. The suspended detection can be manually configured by an operator manipulating a user interface of the air cleaner.

[0013] According to some aspects, the particle sensor data is averaged over an averaging time period of at least 2 seconds, and preferably more than 5 seconds, and even more preferably between 6-10 seconds. This averaging operation suppresses spurious peaks in the particle concentration data, and also removes some of the measurement noise which could otherwise hamper detection performance.

[0014] The particle sensor arrangement is preferably configured to detect a concentration of particles of size about 0,3 ^im. Some particle sensor arrangements are designed to detect levels of different particle sizes, and thus provide more than one particle concentration value output.

[0015] The particle sensor arrangement optionally comprises an intake air guide that is arranged to guide an air flow into the particle sensor of the particle sensor arrangement. The intake air guide can for instance be arranged as a sort of funnel of air guiding hood which directs a part of the main air flow of the air filtration equipment into the particle sensor. The particle sensor thus receives a stronger and more consistent flow of air which helps the particle sensor to detect particle concentration more reliably.

[0016] The particle sensor arrangement may also comprise an exhaust air guide that is arranged to guide an air flow out from the particle sensor of the particle sensor arrangement. The exhaust air guide promotes a more even flow of air past the particle sensor. The exhaust air guide can for instance alleviate problems with backdraught in connection to the exhaust of the particle sensor arrangement.

[0017] According to a preferred embodiment, the particle sensor arrangement comprises a sensor fan that is arranged to generate a sensor air flow past a particle sensor of the particle sensor arrangement. The air filtration equipment may then be configured to operate the sensor fan during a sensor clean-out time period prior to determining the particle sensor data during a measurement time period. Operating the sensor fan during the sensor clean-out time period before actually making a particle concentration measurement by the sensor unit cleans out any remaining dust from previous measurements by the particle sensor arrangement. This increases the reliability of the particle sensor arrangement, especially when the air filtration equipment is intended for use at construction work sites where dust may be present in large amounts.

[0018] The control unit is preferably configured to evaluate particle concentration in the filtered air flow in a repeating pattern, where each repetition in the repeating pattern comprises a particle concentration measurement cycle followed by a waiting time period. In other words, the control unit activates the particle sensor arrangement from time to time to check the particle levels in the filtered air flow, and inactivates the particle sensor there inbetween. It has been realized that the particle sensor arrangement does not have to be operated continuously in order to provide reliable detection of filter leakage. For many air filtration operations, it is sufficient that the particle sensor arrangement is operated periodically in this manner. The waiting time period prolongs the lifetime of the particle sensor arrangement, in particular if the particle sensor arrangement comprises an internal fan that is operated during the particle concentration measurement cycle. The waiting time period is preferably at least 10 minutes long, and more preferably about 15 minutes long. According to some aspects the repeating pattern is an at least partly random pattern, where the particle sensor arrangement is activated with at least partly randomized waiting times and / or at least partly randomized particle concentration measurement cycle time durations.

[0019] According to some aspects, the air filtration equipment comprises a dust measurement chamber with an inlet and an outlet, where the particle sensor arrangement is arranged in an internal volume of the dust measurement chamber. The inlet to the dust measurement chamber can comprise an actuator that is arranged to open and to close the inlet, e.g., in response to a control signal from the control unit. Dust is allowed to pass into the internal volume when the inlet is open and at least partly prevented from passing into the internal volume when the inlet is closed. This way the particle sensor arrangement is only subject to dust when a measurement is to be made. In the time periods between particle concentration measurements the particle sensor is protected from dust, which is an advantage. The dust measurement chamber protects the particle sensor arrangement during storage of the air filtration equipment, and also during transport, when the air filtration equipment may be subject to significant amounts of dust that can have a detrimental effect on the performance of the particle sensor arrangement once it is put to use.

[0020] The air filtration equipment optionally comprises a pressure sensor configured to measure an air pressure between the one or more air filters and the fan. The control unit is configured to suspend detection of air filter leakage in case the measured air pressure fails to satisfy an air pressure acceptance criterion. It has been realized that many particle sensor devices become unreliable at low air pressures, and in particular if the air pressure fluctuates. By making sure that the air pressure is satisfactory before attempting to detect filter leakage the number of false alarms can be reduced significantly, which is an advantage. The air pressure acceptance criterion may comprise an air pressure in a range from ambient air pressure to 1 kPa below ambient air pressure, and preferably an air pressure in a range from ambient air pressure to 650 Pa below ambient air pressure. This feature may be particularly important when the air filtration equipment is an air cleaner.

[0021] The air filtration equipment optionally comprises a temperature sensor configured to measure an operating temperature drift of the air filtration equipment. The control unit can then be configured to suspend detection of air filter leakage in case the operating temperature drift fails to satisfy a temperature drift acceptance criterion. Some particle sensors are prone to give unreliable output data if the temperature drift is too large. By monitoring temperature drift in this manner, the false alarm rate of the particle sensor arrangement can be reduced.

[0022] According to some aspects, the air filtration equipment comprises a plurality of particle sensors arranged interleaved with a plurality of air filters of the air filtration equipment. The control unit can then be arranged to determine which out of the plurality of air filters that is associated with leakage based on a comparison of particle sensor data from the plurality of particle sensors, which is an advantage. The control unit can also be configured to detect when a filter is fully functional, in addition to providing the filter leakage detection function. A problem associated with filter leakage detection based on measurement of particles in the filtered air flow is that a particle sensor arranged after a filter will only detect particles in the filtered air flow of a broken filter if there are particles upstream of the filter. A fault in a filter which is used to filter perfectly clean air cannot be detected by means of a particle sensor. A particle sensor arranged upstream from a filter can be used to understand if a particle sensor arranged downstream from the filter is not detecting any particles because the filter is intact or if the lack of detected particles may be due to that there are no particles to be filtered.

[0023] The air filtration equipment may also comprise a first gas sensor and a second gas sensor arranged upstream and downstream from an additional filter of the air filtration equipment arranged to filter gas, such as an activated carbon filter. The control unit can then be arranged to detect leakage in the additional filter based on a comparison of sensor data from the first gas sensor and the second gas sensor. Placing a gas sensor downstream from the additional filter will only allow detection of filter leakage in case there is gas to be filtered in the ambient environment of the air filtration equipment, similar to the case for particles discussed above. If there is no gas in the air to start with, then of course no gas sensor will provide a positive output signal regardless of the state of the filter. By placing gas sensors both upstream and downstream from the additional filter arranged to filter gas, the filter function can be verified in a more reliable manner.

[0024] The first gas sensor and the second gas sensor are preferably arranged immediately upstream and immediately downstream from the additional filter of the air filtration equipment arranged to filter gas, i.e., without any other filters inbetween the gas filter 125 and the gas sensors.

[0025] According to some aspects, the control unit can be configured to determine a remaining filter capacity of the additional filter based on the comparison of sensor data from the first gas sensor and the second gas sensor. By comparing the outputs of the first and second gas sensor, the control unit can determine or at least estimate how much of the gas present in the air to be filtered that is being captured by the gas filter. Most filters that are arranged to filter gas, such as filters arranged to capture volatile organic and inorganic compounds in an air flow, are gradually spent as they are used. The efficiency or ability to remove gas from the filtered air flow gradually decreases from a maximum filtering efficiency for a new filter down to a reduced filtering capacity for a spent filter. By comparing how much gas that is removed by a filter its age of filtration capability can be determined by the control unit. In this way the control unit can be configured to determine a remaining filter lifetime of the additional filter based on the comparison of sensor data from the first gas sensor and the second gas sensor over a time period. This remaining filter lifetime of remaining filtering capacity can be communicated to an operator, which then knows when it is time to replace the filter with a new one in order to maintain filtering operation at an acceptable level. Some air filters, in particular filters arranged to filter gas and other volatile compounds from an air flow change color and / or texture as they become spent. This change in color and / or texture can be detected by means of a visual sensor such as a camera or photodiode and lens arrangement. Thus, according to some aspects, the air filtration equipment comprises an additional filter arranged to filter gas, and an image capturing device or photovoltaic sensor arranged to capture an image of the additional filter. The control unit can then be configured to determine a remaining filter capacity of the additional filter based on the captured image. The visual sensor monitors the appearance of the additional filter arranged to filter gas, and thus sees when it changes color and / or texture as it is being spent. This way the control unit can determine at least approximately what the remaining filtering capacity of the additional filter is at any given point in time, which is an advantage. The control unit can also be configured to determine a remaining filter lifetime of the additional filter based on a comparison of two or more captured images over a time period, since then the control unit can determine how fast the filter is being spent. The quicker the filter is being spent the shorter the remaining lifetime of the filter. The control unit can also be arranged to trigger generation of a notification, e.g., to an operator of the equipment, in case the filtering capacity of the additional filter fails to satisfy an acceptance criterion. The operator then understands when it is time to replace the gas filter of the equipment, which is an advantage.

[0026] There are also disclosed methods and control units associated with the same advantages as discussed above in connection to the different apparatuses.

[0027] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present disclosure will now be described in more detail with reference to the appended drawings, where:

[0029] Figures 1 A-B schematically show an example air cleaner;

[0030] Figure 2 illustrates a particle sensor arrangement comprising a sensor fan;

[0031] Figure 3 schematically illustrates an air cleaning process;

[0032] Figure 4 shows an example dust measurement chamber;

[0033] Figure 5 shows an example time sequence of air cleaner operations;

[0034] Figures 6A-C are flow charts illustrating example methods;

[0035] Figure 7 shows a control unit comprising processing circuitry;

[0036] Figure 8 schematically illustrates an air cleaner with several particle sensors;

[0037] Figures 9A-B show an example dust extractor;

[0038] Figures 10A-C schematically illustrate an example particle sensor arrangement; and

[0039] Figure 11 shows a filter with upstream and downstream gas sensors;

[0040] DETAILED DESCRIPTION

[0041] Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings. The different devices and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0042] The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0043] An air cleaner is a device which filters the ambient air on a location such as a construction site, workshop, paintshop or laboratory. The present disclosure relates mainly to air cleaners for use at construction sites to remove unwanted matter, such as dust and harmful gas, from the ambient air at the construction site. The air cleaners discussed herein may, for instance, be used to capture fine particle concrete dust generated by a floor grinding operation or from the use of cut-off tools and core drilling equipment. Some of the air cleaners disclosed herein may be connected via sleeve coupling to a suction hose, to draw air in through the suction hose and filter the air before releasing the filtered air into the ambient environment.

[0044] Air cleaners comprise a fan arranged to draw air through some form of filter arrangement, often a pre-filter followed by an essential filter. An impact protection grate may be arranged in front of the filters to protect them from impact by foreign objects at the work site. The air cleaner body of an industrial grade heavy-duty air cleaner is normally a sturdy structure of rugged design.

[0045] An air cleaner used to filter ambient air at a work site or at some other location is an example of more general air filtration equipment. A dust extractor used to filter a particle-laden suction air flow from a dust generating machine is another example of air filtration equipment. It is appreciated that most of the filter leakage detection techniques discussed herein are applicable in both air cleaners of the sort illustrated in Figures 1 A-B and in heavy-duty dust extractors such as the machine shown in Figures 9A-B.

[0046] Figures 9A-B illustrates an example heavy-duty dust extractor 900. The dust extractor 900 can be connected via a hose to a dust generator (not shown in Figure 1 ), such as a core drill, a floor grinder, a concrete saw, or the like. The dust and slurry from the dust generator enters the dust extractor via an inlet 910 (shown closed by a lid in Figures 9A-B) which opens up into a cyclone tank 920 configured to separate out larger debris and particles from the particle-laden airflow that enters the inlet 910.

[0047] The material accumulated in the cyclone tank 920 can be emptied into a dust container, such as a plastic bag or a bucket, located underneath the cyclone tank 920. The Longopac plastic bag system is a well-known dust container option suitable for heavy-duty dust extractors of the kind exemplified in Figures 9A-B.

[0048] A prefilter 930 is arranged in the cyclone tank 920 after the inlet 910, i.e., downstream with respect to the airflow direction.

[0049] The example dust extractor 900 comprises a lid 940 which is closed during operation of the dust extractor 900. The lid 940 can be opened to expose the prefilter 930 as shown in Figure 9A. The air flow entering the dust extractor via the inlet 910 first passes through the cyclone tank 920, then through the prefilter 930, and onwards through air conduits formed in the lid 940 before entering the aperture 950 to the essential filter 960 and onwards towards the fan 160 that generates the suction air flow of the dust extractor 900.

[0050] The example dust extractor 900 comprises a body 101 arranged to support various air filters, such as the pre-filter 930 and the essential filter 960, a fan 160 arranged to generate the working air flow of the dust extractor, a control unit 150, and a particle sensor arrangement 190. The particle sensor arrangement may comprise sensors arranged between the pre-filter 930 and the essential filter 960, and also downstream from the essential filter 960 as schematically illustrated in Figures 9A-B.

[0051] One or more finer particle air filters 960 may be arranged downstream from the prefilter 930 in a dust extractor.

[0052] Particle filters are discussed in, e.g., the International Electrotechnical Commission (IEC) standard 60335-2-69. The essential filter, i.e., the finer filter arranged downstream from the coarser pre-filter in the air cleaners and dust extractors discussed herein, is sometimes referred to as a high efficiency particulate arresting (HEPA) filter. The term essential filter is sometimes also used to describe an air filter device with the ability to trap fine particles of dust.

[0053] HEPA stands for High-Efficiency Particulate Air, a filtration standard used to describe filters that can trap a high percentage of microscopic particles. To be classified as a true HEPA filter, the filter media must meet performance criteria established by international standards. Two of the most recognized are EN 1822 (European Norm) that classifies filters from E10 to U17 based on their efficiency at the Most Penetrating Particle Size (MPPS), typically around 0.1-0.3 microns. ISO 29463 is a global adaptation of EN 1822 with similar classification logic. Within these standards, H13 and H14 filters are the most frequently used for high-performance air cleaning. Both belong to the HEPA range, but they serve different needs based on their filtration efficiency and system compatibility. H13 and H14 filters are generally known and will therefore not be discussed in more detail herein.

[0054] F7, F8, F9 are types of fine filter media defined in EN 779:2012 which was replaced by the standard ISO 16890 although the denominations F7, F8, and F9 are still being used.

[0055] The direction of the flow of air generated by the fan is used herein to describe relative positions of various components in relation to each other. A first component upstream from a second component receives the flow of air before it reaches the second component. The air stream through the air cleaner 100 and the dust extractor 900 preferably but not necessarily first passes a pre-filter, then an essential filter, before reaching the fan. However, the fan can also be placed upstream of the filters, or inbetween the pre-filter and the essential filter. There may also be more than one fan in an air cleaner and in a dust extractor. Both serially arranged fans and fans arranged in parallel are possible. More than two filters are also possible, such as an additional activated carbon filter.

[0056] The fan can, generally, be powered from electrical mains or by battery.

[0057] A pre-filter, such as the filter 120 in Figure 1 A or the pre-filter 930 in Figure 9A, is a relatively coarse filter which traps larger particles, while the essential filter 110, 960 is a finer filter that is able to trap very small particles. The fine particle dust trapped by the essential filter is often considered more harmful to a person compared to the coarser particles trapped by the pre-filter.

[0058] Figures 1 A and 1 B schematically illustrate an air cleaner 100 with an air cleaner body 101 according to an example of the techniques and technical features discussed herein. Figure 1 A is a perspective view from the front and Figure 1 B is an exploded view. Note that a side section of the body 101 has been removed to show the fan 160 in Figure 1 A. The air cleaner body is normally sealed.

[0059] It is appreciated that most of the components seen on the air filters are not inextricably linked to each other. In other words, many of the components can be used separately from each other and do not require each other to provide their respective technical effects, as will be appreciated by the skilled person.

[0060] The air cleaner body 101 in the illustrated examples is of a general cuboid shape with rectangular sides and rounded corners. A cuboid shape is a box-like shape with rightangle corners. The air cleaner body 101 has a main air intake aperture 102 through which an air flow generated by a fan 160 is drawn into the air cleaner and filtered before it is released back into the ambient environment. The air cleaner body 101 normally encloses an internal volume of the air cleaner, as shown in Figure 1 B.

[0061] The air is cleansed from coarse particulate matter by an optional pre-filter 120 followed by an essential filter 110 which removes more fine particulate matter. The air cleaner has an outlet (not shown) after the fan, which releases the filtered air back into the environment. An impact protection grate 130 protects the air cleaner filters from mechanical damage by objects at the work site.

[0062] The air cleaner has a lid portion 140 which among other things comprises a user interface 155 and handles 145 arranged at opposing sides of the lid portion 140.

[0063] A control unit 150 of the air cleaner is arranged to control various functions of the air cleaner 100, such as an automated filter leakage detection function that will be described in more detail below. The control unit 150 is only schematically illustrated in Figures 1 A-B.

[0064] Some air cleaners also comprise additional filters 125, such as activated carbon filters, which are arranged to filter volatile compounds from the air, i.e., organic and inorganic gasses and the like. The example air cleaner 100 in Figure 1 B comprises an additional filter 125 which fits in a matching recess 126 formed in the separating wall 165. An additional filter such as an activated carbon filter can thus be inserted inbetween the fan and the essential filter if desired and left out of the assembly if not deemed necessary for a given air filtering operation, without other modifications to the air cleaner.

[0065] The essential filter 110 in the illustrated example is in sealing contact with the separating wall 165 around a peripheral contact surface 180 of the essential filter 110, which periphery extends beyond the periphery of the additional filter 125. The peripheral contact surface 180 extends in a plane parallel to a filter plane F.

[0066] The fan 160 is in the example of Figures 1 A-B arranged supported by the separating wall 165, where it draws air through a fan aperture formed in the separating wall. It is preferred that the fan is arranged downstream of the pre-filter 120 and the essential filter 110, and also downstream of the additional filter 125 if present. However, it is appreciated that the fan 160 can be arranged upstream of the filters, downstream of the filters, or inbetween the pre-filter and the essential filter. More than one fan can also be used, as mentioned above. Either in serial configuration or in parallel configuration.

[0067] An air conduit, such as a tubular member, may be arranged extending from a pressure sensor 191 inside the lid portion 140 to an aperture that opens up into the volume formed between the separating wall 165 and the essential filter 110. The aperture is not shown in the drawings. The pressure sensor allows a control unit of the air cleaner 100 to monitor the air pressure in the volume formed between the essential filter 110 and the separating wall 165, and to detect events such as a particle laden filter. A particle laden filter, i.e., a clogged filter, will result in a decrease in pressure in the volume between the essential filter and the fan. Other types of pressure sensors 191 can also be used to measure the pressure downstream from the essential filter 110.

[0068] One or more temperature sensors 192 can be used to measure ambient temperature outside the air cleaner body 101 and / or an internal operating temperature of the air cleaner 100.

[0069] A particle sensor arrangement 190, schematically illustrated in Figure 1 B, can be arranged downstream of the fan 160 and the separating wall 165, or at least downstream of the essential filter 110, to monitor particle levels in the filtered air.

[0070] Light scattering is one of the most widely used principles for air particle concentration sensors due to its versatility, compact design, and ability to provide real-time data. Particle sensors based on light scattering comprise a light source such as a light emitting diode (LED) or a laser and a photodetector. Light emitted from the light source is scattered by particles in the air and the scattered light is picked up by the photodetector which generates an output signal indicative of the amount of particles in the air. The more particles the air comprises, the more light is scattered by the particles and detected by the photodetector. The intensity and pattern of scattered light correlate with the size and concentration of particles. Thus, some particle sensors are also able to detect the size distribution of particles in the air. An internal sensor fan is used to transport particle-laden air past the light source and photodetector.

[0071] Other types of particle sensors, based on other operating principles, can of course also be used in the air cleaners described herein.

[0072] An example particle sensor arrangement 190 is schematically illustrated in Figure 2. The particle sensor arrangement 190 comprises an air inlet 200. An internal sensor fan 210 which is normally different from the main fan 160 of the air cleaner, generates an air flow 220 past a particle sensor 230, such as a light scattering based sensor as discussed above. The particle sensor 230 then generates an output signal 240 indicative of the amount of dust in the air flow 220, which signal optionally also comprises data related to a particle size distribution of the dust in the air flow 220.

[0073] The output signal 240 may be an analog signal, such as a voltage or current signal, or a digital signal. The output signal may be transmitted to the control unit 150 for further processing. The control unit 150 or some other control device of the air cleaner 100 may be arranged to control the sensor fan 210, e.g., to start and stop the sensor fan 210, and according to some examples also control a fan speed of the sensor fan 210, e.g., to maintain a desired air flow level past the sensor device 230.

[0074] With reference to Figures 10A-C, the particle sensor arrangement 190 optionally comprises an intake air guide 1000 arranged to guide an air flow towards the sensor part of the particle sensor arrangement 190, and optionally also an exhaust air guide 1010 arranged to guide an air flow away from the sensor part of the particle sensor arrangement 190. Figure 10A shows a part of the fan 160 which is used to draw air through the air cleaner 100. A similar type of fan or impeller can be used to generate the suction air flow in a heavy-duty dust extractor of the sort shown in Figures 9A-B. The fan 160 is arranged in a fan housing 1030 to generate a rotation of the air in a known manner. A part of the air flow generated by the fan 160 is guided by the intake air guide 1000 towards the sensor part of the particle sensor arrangement 190 which in this case is mounted in connection to the fan housing 1030. The particle sensor thus receives enough of the filtered air flow to detect particle concentration in a reliable manner.

[0075] Figure 10B shows a more detailed perspective view of the example intake air guide 1000. Figure 10B shows a bottom view of the air guide for the particle sensor arrangement 190. The intake air guide 1000 in this case resembles a typer of scoop or hood which guides air from a location inside the fan housing towards the particle sensor. An example exhaust air guide 1010 also comprises a sort of scoop of hood, but facing in the opposite direction compared to the intake air guide. The exhaust air guide 1010 is designed to reduce disturbances at the exhaust of the particle sensor arrangement 190. The directions of the air flow into the particle sensor and out from the particle sensor are marked as IN and as OUT in Figures 10B-C, respectively.

[0076] The arrangement in Figures 10A-C also comprises a mounting plate 1020 arranged to be attached to the fan housing or at some other suitable location along the path of the air flow in the air filtration equipment.

[0077] It is appreciated that the particle sensor embodiment in Figures 10A-C is just an example. There are many ways in which the intake air guide and the exhaust air guide can be designed to promote the operation of the particle sensor arrangement.

[0078] Particle sensor data related to the particle concentration in the filtered air flow, obtained downstream from the one or more air filters 110, 120, 125, 930, 960, can be used to detect filter leakage. An unexpectedly high particle concentration downstream from the air filters is indicative of a malfunctioning air filter. Filter leakage may be caused by damage to the filter media, filter wear such as aging seals and the like, or manufacturing errors. It is of course desired to quickly detect when filter leakage occurs, since then the air filtration equipment may not be performing its intended function, which may result in hazard to personnel at a work site due to high particle concentrations in the ambient air.

[0079] Obtaining reliable and accurate particle sensor data from a particle sensor in heavy- duty air filtration equipment such as the air cleaner 100 in Figures 1 A-B and the dust extractor 900 in Figures 9A-B is challenging. The amount of dust which can be present at construction work sites is often significant and tends to accumulate in air filtration equipment, which may cause inaccurate particle sensor outputs. Fluctuations in the air flow through an air cleaner may also cause inaccuracies in the obtained particle sensor data. Obtaining reliable particle sensor data in the filtered suction air flow in a dust extractor is also challenging due to variation in air flow and the tendency of particulate matter to accumulate in the dust extractor during transport and storage of the dust extractor.

[0080] Due to these challenges, the number of false alarms may be significant. To reduce the number of false alarms the detection margins can be increased, but this leads to less sensitive filter leakage detection systems which may fail to detect filter leakage.

[0081] Figure 3 illustrates a sequence of operations 300 which can be performed in an air cleaner such as the air cleaner 100 shown in Figures 1 A-B or in a dust extractor such as the dust extractor 900 in Figures 9A-B. Optional elements and operations are illustrated by dashed line in Figure 3. An inlet air flow first passes via an optional prefilter 120 before passing the essential filter 110 of the air cleaner 100. An additional filter 125 such as an activated carbon filter may be arranged along the air flow. One or more optional pressure sensors 191 and / or temperature sensors 192 are also arranged along the air flow through the air cleaner.

[0082] A fan 160 is arranged downstream from the one or more filters 110, 120, 125, 930, 960, followed by a particle sensor arrangement 190. The output signal 240 from the particle sensor arrangement 190 is transmitted as particle sensor data related to the particle concentration in the filtered air flow to the control unit 150, which performs a filter leakage detection operation. To reduce the number of false alarms in the filter leakage detection function of the air filtration equipment, while maintaining an acceptable filter leakage detection performance, a number of improvements are proposed herein. It is understood that these improvements are not inextricably linked to each other, i.e., they can be implemented separately from each other. However, particular advantages are obtained if the improvements are implemented together.

[0083] Some improvements are more suited to air cleaners, while other improvements are more suited to dust extractors, although most if not all improvements are applicable in both types of dust filtration equipment.

[0084] Some of the main improvements to filter leakage detection in industrial air filtration equipment, such as air cleaners and dust extractors, described herein comprise;

[0085] 1. Allowing a start-up time period to pass from activation of the air filtration equipment 100, 900 until filter leakage detection is activated, in order to clear out old dust from the particle sensor device before attempting to detect filter leakage.

[0086] 2. Operating the sensor fan of the particle sensor arrangement during a sensor clean-out time period prior to determining the particle sensor data during a measurement time period. This sensor clean-out time period removes any residual dust from previous measurements, resulting in a more reliable dust measurement operation by the particle sensor arrangement.

[0087] 3. Adding a dust measurement chamber to the air filtration equipment, which can be selectively filled with potentially particle-laden air in preparation for a particle concentration measurement operation by the particle sensor. The dust measurement chamber acts as a type of airlock which prevents particles from accumulating in connection to the sensor inbetween measurements, and also during time periods when the air filtration equipment is not active, such as during transport.

[0088] 4. Performing filter leakage detection by evaluating particle concentration in the filtered air flow in a repetitive manner, such as in a repeating pattern, where each repetition in the repeating pattern comprises a particle concentration measurement cycle followed by a waiting time period. This prolongs the lifetime of the particle sensor arrangement, and avoids overloading the internal sensor fan. The repeating pattern may be a fixed consistent pattern or an at least partly randomized pattern. Y1

[0089] 5. Providing one or more pressure sensors and / or temperature sensors to establish that conditions for obtaining particle concentration data from the particle sensor are favorable. This reduces the number of false alarms due to inaccurate readings from the particle sensor arrangement.

[0090] To summarize, some aspects of the present disclosure relate to air filtration equipment 100,900 comprising a body 101 such as an air cleaner body or a dust extractor body that is arranged to support one or more air filters, such as an essential filter 110, 960, a pre-filter 120, 930, and an additional filter 125 adapted to filter gas, such as an activated carbon filter. The air filtration equipment 100, 900 comprises a fan 160 that is arranged to generate an air flow through the one or more air filters 110, 120, 125, 930, 960, a particle sensor arrangement 190 arranged downstream from the one or more air filters 110, 120, 125, 930, 960 to evaluate a particle concentration in the filtered air flow, and a control unit 150 arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement 190. The particle sensor arrangement 190 is preferably arranged downstream from the fan 160, although other positions are also possible, such as inbetween the pre-filter 120, 930, and the essential filter 110, 960.

[0091] The particle sensor arrangements 190 discussed herein may be configured to detect a concentration of particles of size about 0,3 ^im. Some particle sensor arrangements 190 are capable of detecting separate concentration levels for different sizes of particles. These sensor arrangements are also applicable herein.

[0092] The control unit 150 is configured to detect leakage in at least one air filter out of the one or more air filters 110, 120, 125, 930, 960 in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, such as a predetermined threshold or a more advanced statistical test. The control unit 150 can, for instance, be configured to detect filter leakage if the particle concentration in the filtered air flow exceeds a pre-determined threshold value for at least a given time period. More advanced acceptance criteria may comprise statistical hypothesis testing. A statistical hypothesis test is a method of statistical inference used to decide whether the data sufficiently supports a particular hypothesis, i.e., filter leakage or no filter leakage. A statistical hypothesis test typically involves a calculation of a test statistic. Methods for statistical hypothesis testing are generally known and will therefore not be discussed in more detail herein. In case the particle sensor arrangement is able to distinguish different particle concentrations for different particle sizes, then the acceptance criteria may be set for each detectable particle size range. A pre-filter 120, 930 may for instance be allowed to pass smaller particles, while an essential filter 110, 960 should have more strict requirements on letting smaller particles pass the filter. A missing filter condition can of course also be detected by the control unit 150 in this manner, since a missing filter can be seen as a large leak or malfunction in the filtering chain of the air filtration equipment.

[0093] To avoid false alarms due to previously accumulated dust in vicinity of the particle sensor, the detection of filter leakage by the control unit 150 is conditioned on that a start-up time period has passed from activation of the air filtration equipment 100, 900. Thus, when an operator activates the air filtration equipment, i.e., turns on the fan 160 to filter air at the construction site or generate a suction air flow by a dust extractor, the filter leakage detection function is initially inactivated. The air filtration equipment interior is then gradually cleaned from old dust, as long as the filtering system works of course.

[0094] Figure 5 shows example operations 500 of an example air cleaner such as the air cleaner 100 discussed above. The air cleaner is activated at time T=0, i.e., the air cleaner fan 160 is turned on and air starts to flow through the filters of the air cleaner. Note the start-up waiting interval 510. The start-up time period 510 is preferably at least 30 seconds, and more preferably at least 1 minute, and even more preferably at least 5 minutes, such as about 8 minutes.

[0095] To improve the quality of the particle sensor data, it can be averaged over an averaging time period. This averaging time period is suitable at least 2 seconds for the type of air cleaners discussed herein, and preferably more than 5 seconds, and even more preferably between 6-10 seconds. The averaging time period smoothens out any spurious peaks in the particle concentration data, and also suppresses noise in the data from the particle sensor. The averaging may be performed as a running average, possibly with some weighting to emphasize recent sensor samples over past sensor samples.

[0096] With reference to the example operations 500 shown in Figure 5, the control unit 150 is optionally configured to evaluate particle concentration in the filtered air flow in a repeating pattern, where each repetition in the repeating pattern comprises a particle concentration measurement cycle 520 followed by a waiting time period 550. This means that the particle sensor 190 is not operated continuously, but periodically, which prolongs the lifetime of the particle sensor. The waiting time period 550 may be at least 10 minutes long, and preferably about 15 minutes long. The features related to the particle concentration measurement cycle 520 followed by the waiting time period 550 are not inextricably linked to the other operations and features, but can be practiced in a stand-alone manner. This function can of course also be used in a heavy-duty dust extractor 900.

[0097] The particle sensor arrangement 190 preferably comprises an internal sensor fan 210, different from the main air filtration equipment fan 160, arranged to generate a sensor air flow 220 past a particle sensor 230, as discussed above in connection to Figure 2. The air filtration equipment 100, 900 is according to some aspects configured to operate the sensor fan 210 during a sensor clean-out time period 530 prior to determining the particle sensor data during a measurement time period 540, as shown in Figure 5. The sensor fan ON-time may be considerably longer than the actual measurement time, to make sure that the particle sensor is clean before attempting to measure particle concentration. According to an example, the sensor clean-out time period 530 is between 3-7 minutes, such as about 5 minutes, and the measurement time period 540 is between 1 -3 minutes, such as about 2 minutes. The features related to the sensor clean-out time period 530 are not inextricably linked to the other operations and features, but can be practiced in a stand-alone manner.

[0098] It is appreciated that both the sensor clean-out time period 530, the measurement time period 540, and the waiting time period 550 may be at least partly randomized such that one or more of the time periods vary from one repetition to another repetition in the pattern. The time durations may for instance be drawn from a uniform random distribution defined over a given time range, or from a normal distribution with a given mean and a given variance. According to a suggested implementation the sensor clean-out time period 530 is randomized around a mean duration of about 5 minutes, the measurement time period 540 is randomized around a mean duration of about 2 minutes, and the waiting time period 550 is randomized around a mean duration of about 15 minutes.

[0099] Figure 4 schematically shows a dust measurement chamber 400 that can be arranged in an air cleaner 100 such as the air cleaner discussed above or in a dust extractor such as the machine 900 shown in Figures 9A-B. The dust measurement chamber acts like an air lock which separates the particle sensor from the rest of the air filtration equipment, and perhaps more importantly from the ambient environment, when the particle sensor is not being used to sample particle concentrations in the filtered air. The dust chamber can be opened up to let potentially particle-laden air in, which air is then analyzed by the particle sensor 190, and then sealed again when the measurement is completed.

[0100] The example dust measurement chamber 400 in Figure 4 comprises an inlet 410 and an outlet 420. The inlet opens up into an internal volume 430 where particle laden air 435 can be analyzed by the particle sensor arrangement 190 which is arranged in the internal volume 430 of the dust measurement chamber 400. The inlet 410 comprises an actuator 440 arranged to open and to close the inlet 410, which actuator can be controlled by the control unit 150. In this example the inlet comprises a Y-valve which allows the control unit 150 to choose between letting unfiltered air into the internal volume 430 via conduit 411 , or if filtered air should be let into the internal volume 430 via the conduit 412 that comprises an inlet filter 450. Air that is let into the internal volume via the filtered air inlet 412 will flush out any remaining articles from the internal chamber 430. Other inlet mechanisms, such as electrically actuated doors and the like can of course also be used. Generally, dust 435 is allowed to pass into the internal volume 430 when the inlet 410 is open and at least partly prevented from passing into the internal volume 430 when the inlet 410 is closed. The inlet mechanism can be actuated in response to a control signal from the control unit 150.

[0101] An actuator 460 may also be arranged in connection to the outlet 420 to open and to close the outlet 420, e.g., in response to a control signal from the control unit 150.

[0102] The features related to the dust measurement chamber 400 are not inextricably linked to the other operations and features, but can be practiced in a stand-alone manner. The dust measurement chamber 400 can be used with advantage in an air cleaner 100 and also in a dust extractor 900.

[0103] According to some aspects, the air cleaner 100 is configurable in a fan mode of operation, where the control unit 150 is configured to suspend detection of air filter leakage when the air cleaner operates in the fan mode of operation. Normally the air cleaner is operated without filters when in the fan mode of operation. The dust extractor 900 is normally not operated in a fan mode of operation, although exceptions of course exist.

[0104] Figures 6A-C are flow charts that describe methods which summarize some of the example air filtration operations discussed herein. Figure 6A illustrates a computer implemented method, performed by a control unit 150 in air filtration equipment 100, 900. The air filtration equipment 100, 900 comprising a fan 160 arranged to generate an air flow through one or more air filters 110, 120, 125, 930, 960 of the air filtration equipment 100, 900, and a particle sensor arrangement 190 arranged downstream from the one or more air filters 110, 120, 125, 930, 960 to evaluate a particle concentration in the filtered air flow. The method comprises obtaining Sa1 particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement 190, and detecting Sa2 leakage in at least one air filter out of the one or more air filters 110, 120, 125, 930, 960 in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, where detection of filter leakage by the control unit 150 is conditioned on that a startup time period 510 has passed from activation of the air filtration equipment 100, 900.

[0105] Figure 6B illustrates a computer implemented method, performed by a control unit 150 in air filtration equipment 100, 900. The air filtration equipment 100, 900 comprising a fan 160 arranged to generate an air flow through one or more air filters 110, 120, 125, 930, 960 of the air filtration equipment 100, 900, and a particle sensor arrangement 190 arranged downstream from the one or more air filters 110, 120, 125, 930, 960 to evaluate a particle concentration in the filtered air flow. The method comprises, repeatedly, obtaining Sb1 particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement 190 during a particle concentration measurement cycle 520, followed by waiting Sb2 during a waiting time period 550.

[0106] Figure 6C illustrates a computer implemented method, performed by a control unit 150 in air filtration equipment 100, 900. The air cleaner 100 comprising a fan 160 arranged to generate an air flow through one or more air filters 110, 120, 125, 930, 960 of the air filtration equipment 100, 900, and a particle sensor arrangement 190 arranged downstream from the one or more air filters 110, 120, 125, 930, 960 to evaluate a particle concentration in the filtered air flow, where the particle sensor arrangement 190 comprises a sensor fan 210 arranged to generate a sensor air flow 220 past a particle sensor 230. The method comprises, repeatedly, operating Sc1 the sensor fan 210 during a sensor clean-out time period 530, followed by obtaining Sc2 particle sensor data related to a particle concentration in the filtered air flow from the particle sensor arrangement 190.

[0107] According to some aspects, the air filtration equipment 100, 900 comprises a pressure sensor 191 configured to measure an air pressure between the one or more air filters 110, 120, 125, 930, 960 and the fan 160, as schematically illustrated in Figure 3. The control unit 160 can be configured to suspend detection of air filter leakage in case the measured air pressure fails to satisfy an air pressure acceptance criterion. The air pressure acceptance criterion may for instance comprises an air pressure in a range from ambient air pressure to 1 kPa below ambient air pressure, and preferably an air pressure in a range from ambient air pressure to 650 Pa below ambient air pressure. This has the effect of stabilizing the particle concentration detection operation, which can be negatively affected by too low air pressure.

[0108] The air filtration equipment 100, 900 may also comprise a temperature sensor 192, as discussed above, that is configured to measure an operating temperature drift of the air filtration equipment. The control unit 160 is configured to suspend detection of air filter leakage in case the operating temperature drift fails to satisfy a temperature drift acceptance criterion. Accounting for temperature drift in this manner potentially avoids corrupt data out from the particle sensor, which may in some cases be sensitive to large drifts in temperature.

[0109] Some of the air filtration equipment described herein comprise a plurality of particle sensors arranged interleaved with a plurality of air filters 110, 120, 125, 930, 960 of the air filtration equipment 100, 900. The control unit 150 can then be arranged to determine which out of the plurality of air filters 110, 120, 125, 930, 960 that is associated with leakage based on a comparison of particle sensor data from the plurality of particle sensors. The control unit can also in this case determine that a filter is not leaking, i.e. , is performing satisfactorily, based on a comparison of particle sensor data from the plurality of particle sensors. For instance, in case the control unit determines that there is an amount of dust upstream from a given filter, but not downstream, then the filter has removed the dust from the air flow as intended.

[0110] Figure 8 schematically illustrates an example of this kind, where a plurality of particle sensors are interleaved inbetween air filters 120, 110, 125 of air filtration equipment 100, 900. Each sensor provides particle sensor data S1 , S2, S3, S4 indicative of a particle concentration at the respective location in the filter chain. Each particle sensor may be configured to measure particle concentration of one or more particle sizes. In a fully functioning system, it is expected that each filter reduces the particle concentration in a size span corresponding to the type of filter. The pre-filter 120, 930 for instance, is expected to significantly reduce the number of larger particles in the air flow, such as particles larger than 0,5-1 ,0 ^m, and to have a less pronounced effect on the concentration of smaller particles, such as particles with size on the order of 0,3 / rm. The essential filter 110, 960 is expected to remove also smaller particles, such as particles with size around 0,3 / zm. By monitoring the output data from the different particle sensors, the control unit 150 may be able to detect which filter in the filter sequence that is leaking. In some cases, the control unit 150 may also be able to verify that a filter is fully functional, i.e., not leaking. A fully functional filter can be verified in case particle concentration is detected upstream from the filter, but not directly down-stream of the filter. Occurrence of larger particles directly down-stream from the pre-filter 120, 930, i.e., up-stream from the essential filter indicates leakage in the pre-filter. Occurrence of smaller particles downstream from the essential filter is indicative of leakage in the essential filter. In case there are smaller particles upstream from the essential filter, but not downstream, then the essential filter is most likely performing its intended filtering function. Not much can be said about filter function of any of the filters in case there are no particles of the “right” size upstream from a given filter.

[0111] With reference to Figure 11 , the air cleaner 100 and / or the dust extractor 900 may also comprise a first gas sensor 1110 and a second gas sensor 1120 arranged upstream and downstream from an activated carbon filter or other additional filter 125 of the air cleaner arranged to filter gas. In this case the control unit 150 can be arranged to detect leakage in the additional filter 125 arranged to filter gas based on a comparison of sensor data from the first gas sensor 1110 and the second gas sensor 1120. Presence of gas upstream from the filter 125, but not downstream, is an indication of a functional filter. However, nothing can be said about the filter function if there is no gas upstream from the filter 125, since then there is most likely no gas in the ambient air at the work site or in the particle laden suction air flow from the dust generating equipment connected to a dust extractor 900. Presence of gas downstream from the gas filter 125 of the air cleaner or dust extractor is an indication that the filter is not operating as intended.

[0112] It is appreciated that the additional filter 125 can be used as a stand-alone filter without the other filters of the air filtration equipment 100, 900 described herein. The first and second gas sensors 1110, 1120 are not inextricably linked to the particle sensor arrangement 190, but can be used as stand-alone sensors.

[0113] Consequently, there is disclosed air filtration equipment 100, 900 comprising a body 101 arranged to support one or more air filters 110, 120, 125, 930, 960, a control unit 150, and a fan 160 arranged to generate an air flow through the one or more air filters 110, 120, 125, 930, 960. The air filtration equipment 100, 900 further comprises a first gas sensor 1110 and a second gas sensor 1120 arranged upstream and downstream from an additional filter 125 of the air filtration equipment 100, 900 arranged to filter gas, respectively, where the control unit 150 is arranged to detect leakage in the additional 125 based on a comparison of sensor data from the first gas sensor and the second gas sensor.

[0114] The filter 125 can be any filter for filtering volatile organic compounds such as an activated carbon filter, and / or any filter for filtering volatile inorganic compounds.

[0115] Filters designed to remove volatile organic compounds (VOCs) and volatile inorganic compounds (VICs) are generally known. VOCs are carbon-based chemicals that easily evaporate at room temperature and are commonly emitted from solvents, paints, adhesives, fuels, cleaning products, and various manufacturing processes. VICs, on the other hand, are volatile substances not containing carbon — such as ammonia, sulphur dioxide, hydrogen sulphide, and chlorine. Exposure to both groups of compounds can negatively impact human health, cause unpleasant odours, and contribute to environmental problems such as smog formation and corrosion.

[0116] To manage these pollutants, a variety of filtration technologies can be used. One of the most widely applied technologies is activated carbon filtration, which relies on adsorption, a process where molecules adhere to the surface of a solid material. Activated carbon is produced from carbon-rich materials such as coal, coconut shells, or wood, followed by thermal or chemical activation to create an extremely porous structure. The enormous internal surface area — often over 800-1500 m2per gram — gives activated carbon its ability to capture significant quantities of organic vapor molecules. As contaminated air passes through the carbon bed, VOC molecules diffuse into the pores and bind to the carbon surface, effectively removing them from the air stream. Once saturated, activated carbon can be replaced or regenerated through heating or solvent extraction. An activated carbon filter is gradually spent as it is used to filter air and will therefore eventually loose its filtering capability. The remaining filtering capacity of an activated carbon filter can be determined by monitoring how much of a certain gas that is removed by the filter. The gas concentration before and after the filter is compared, and a remaining filter capacity can be determined from the difference. The filtering capacity can be tabulated for a range of differences. An analytical function taking gas concentration before and after the filter as inputs and giving filtering capacity as output can also be derived using laboratory experimentation and / or computer simulation.

[0117] However, activated carbon is not universally effective. It works best on non-polar organic compounds with relatively high molecular weight and boiling points. Highly polar or low-molecular-weight inorganic gases such as ammonia or hydrogen sulphide may require chemical impregnation of the carbon with acids, bases, or oxidizing agents, enabling chemisorption — an irreversible chemical bonding process that neutralizes the contaminant.

[0118] Beyond activated carbon, several other filtration technologies are employed depending on the target contaminants and application. Oxidation-based filtration, such as photocatalytic oxidation (PCO), uses ultraviolet light and catalysts like titanium dioxide to break VOCs down into water and carbon dioxide. Molecular sieve filters, typically composed of zeolites, provide highly selective pore structures that can trap specific gas molecules based on size and polarity. Scrubber systems, often used in industrial exhaust treatment, absorb soluble inorganic gases into liquid solutions.

[0119] Gas sensors that measure concentration of VOCs and VICs in a filtered air flow are generally known in the art and will therefore not be discussed in depth herein. Several different sensor technologies are employed depending on the chemical species to be measured, sensitivity requirements, selectivity, and cost constraints.

[0120] One widely used approach for detecting a broad spectrum of VOCs is the metal oxide semiconductor (MOS) gas sensor. MOS sensors operate by heating a metal oxide layer to a temperature where gas molecules interacting with the surface change its electrical resistance. Many organic vapors and some inorganic gases are oxidized on the sensor surface, producing a measurable electrical response. MOS sensors are durable, inexpensive, and offer high sensitivity down to parts-per-billion (ppb) levels, making them useful for continuous monitoring. However, their selectivity is often limited, meaning they can respond to multiple types of gases and are influenced by humidity and temperature, requiring calibration and environmental compensation.

[0121] For more selective detection of individual VOCs, photoionization detectors (PIDs) are frequently used. A PID uses ultraviolet light to ionize gas molecules. The resulting electrons and ions from the ionization generate an electrical current proportional to the gas concentration. PIDs can detect a wide range of VOCs at extremely low concentrations. However, PIDs cannot detect most inorganic gases, and detection capability depends on the ionization energy of the target compound.

[0122] To monitor VICs such as ammonia, chlorine, nitrogen oxides, or sulfur-containing gases electrochemical gas sensors are a common choice. These sensors contain electrodes and an electrolyte where the target gas participates in a redox reaction, generating an electric current proportional to concentration. Electrochemical sensors provide excellent selectivity, fast response times, and relatively low power consumption, but may be cumbersome to integrate in portable air filtration systems of the sort discussed herein.

[0123] Another technology used in high-precision applications is non-dispersive infrared (NDIR) spectroscopy, which measures the absorption of infrared light by specific gas molecules. NDIR sensors are highly selective for compounds with strong infrared absorption profiles, such as carbon dioxide, methane, and certain VOCs. They are stable and have long lifetimes, but typically detect only one target gas at a time and are larger and more expensive than MOS or electrochemical sensors.

[0124] Combinations of different types of sensors can be integrated to capture a broad range of compounds and verify filter efficiency in real time. By comparing upstream and downstream sensor measurements, operators can detect filter malfunction, when a filter is nearing its end of life, optimize filter replacement schedules, and ensure safe and compliant operation.

[0125] The control unit 150 can be arranged to determine that the additional filter 125 of the air filtration equipment 100, 900 is intact, i.e., not associated with leakage, based on a comparison of sensor data from the first gas sensor and the second gas sensor. This is because the control unit 150 now knows from the upstream gas sensor that there is gas to be filtered. Hence, the fact that the gas concentration level has decreased after the filter is a clear indication that the filter is performing its intended filtration function. The efficiency of the filtration process can also be evaluated by the control unit 150 in this manner.

[0126] The control unit 150 is configured to determine a remaining filter capacity of the additional filter 125 based on the comparison of sensor data from the first gas sensor 1110 and the second gas sensor 1120. Suppose for instance that a given gas filter or volatile compound filter arrangement is specified to remove a given percentage of a certain volatile compound or group of compounds in a given use case. The control unit 150 can determine the quantity of the volatile compounds inbounds to the filter

[0127] 125 that is actually removed by the filter by comparing the outputs of the first and the second gas sensor. The remaining filter capacity can be determined by the control unit 150 using a pre-determined look-up table that has been calibrated a-priori, or an analytical function which has been determined beforehand using, e.g., computer simulation of the filter and / or practical experimentation using a laboratory set-up.

[0128] The control unit 150 can optionally also be configured to determine a remaining filter lifetime of the additional filter 125 based on the comparison of sensor data from the first gas sensor and the second gas sensor over a time period. By monitoring how fast filtering efficiency or filtering capacity decreases over time, an extrapolation can be made by the control unit 150 in order to estimate when in time the filter 125 will be spent and in need of replacement.

[0129] The air filtration equipment 100, 900 optionally comprise an image capturing device

[0130] 126 arranged to capture an image of the additional filter 125. The control unit 150 can then be configured to determine a remaining filter capacity of the additional filter 125 based on the captured image. The image capturing device may be a camera arranged to take photos or video of the filter, or a lens with a photodetector arranged to detect what color the filter surface has.

[0131] Many modern filtration systems designed for VOCs and VICs incorporate visual indicator media that change color or texture when exposed to specific gases. These changes occur due to chemical reactions between the filter’s active material and captured pollutants, signaling that adsorption or neutralization capacity is reaching exhaustion. To automate filter monitoring and avoid manual inspection, optical sensing solutions such as camera-based systems and photodiode sensors can be used to quantify visual changes and determine filter health in real time. Photodiode-based sensing systems offer a simple, compact, and cost-effective method for monitoring color changes. A photodiode converts incident light intensity into an electrical signal that varies according to the wavelength and intensity of light reflected or transmitted by the filter material. In a typical setup, an LED light source illuminates a specific region of the filter, and the photodiode measures reflected light. As the filter becomes saturated with contaminants, its color shifts (for example, from light brown to dark gray), changing the reflectance profile and therefore the photodiode output. Multiple photodiodes tuned for different wavelength bands (red, green, blue, or near-infrared) can be used to produce a more precise color signature.

[0132] Camera-based sensors provide higher resolution data and the ability to analyze both color and texture changes in the additional filter 125. A camera system typically includes a controlled lighting setup to ensure consistent illumination, a fixed lens for stable image acquisition, and image processing algorithms that evaluate filter surface appearance overtime. Digital image analysis can extract parameters such as average color values, contrast, edge density, or surface roughness patterns. Texture analysis algorithms can detect subtle structural changes that may indicate saturation, cracking, fouling, or uneven loading across the filter surface.

[0133] The control unit 150 can also be configured to determine a remaining filter lifetime of the additional filter 125 based on a comparison of two or more captured images over a time period, since comparing two or more captured images (or one or more video sequences) over a time period allows the control unit to determine how fast the filter changes surface color and / or surface texture. The control unit 150 can extrapolate the rate of change to determine when the filter 125 will have reached its end of life.

[0134] The control unit 150 is optionally arranged to trigger generation of a notification in case the filtering capacity of the additional filter 125 fails to satisfy an acceptance criterion.

[0135] Figure 7 schematically illustrates, in terms of a number of functional units, the general components of a control unit 150, 700. It is appreciated that the control units 150 discussed herein can be located on a single printed circuit board (PCB) or on several PCBs. The control unit 150 may comprise a single circuit or a plurality of separated circuits.

[0136] Generally, processing circuitry 710 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 730. The processing circuitry 710 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0137] Particularly, the processing circuitry 710 is configured to cause the control unit 150 to perform a set of operations, or steps, such as the methods discussed herein. For example, the storage medium 730 may store the set of operations, and the processing circuitry 710 may be configured to retrieve the set of operations from the storage medium 730 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 710 is thereby arranged to execute methods as herein disclosed.

[0138] The storage medium 730 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0139] The device 150, 700 may further comprise an interface 720 for communications with at least one external device, such as a dust extractor or the like. As such the interface 720 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[0140] The processing circuitry 710 controls the general operation of the control unit 150, 700, e.g., by sending data and control signals to the interface 720 and the storage medium 730, by receiving data and reports from the interface 720, and by retrieving data and instructions from the storage medium 730.

[0141] There is also disclosed herein a computer readable medium carrying a computer program comprising program code means for performing the methods discussed herein, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product.

Claims

1. CLAIMS1 . Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, where detection of filter leakage by the control unit (150) is conditioned on that a startup time period (510) has passed from activation of the air filtration equipment (100, 900) .

2. The air filtration equipment (100, 900) according to claim 1 , where the particle sensor arrangement (190) is arranged downstream from the fan (160).

3. The air filtration equipment (100, 900) according to claim 1 or 2, where the particle sensor data is averaged over an averaging time period of at least 2 seconds, and preferably more than 5 seconds, and even more preferably between 6-10 seconds.

4. The air filtration equipment (100, 900) according to any previous claim, where the start-up time period (510) is at least 30 seconds, and preferably at least 1 minute, and more preferably at least 5 minutes, such as about 8 minutes.

5. The air filtration equipment (100, 900) according to any previous claim, where the control unit (150) is configured to evaluate particle concentration in the filtered air flow in a repeating pattern, where each repetition in the repeating pattern comprises a particle concentration measurement cycle (520) followed by a waiting time period (550).

6. The air filtration equipment (100, 900) according to claim 5, where the waiting time period (550) is at least 10 minutes long, and preferably about 15 minutes long.

7. The air filtration equipment (100, 900) according to any previous claim, where the particle sensor arrangement (190) comprises a sensor fan (210) arranged to generate a sensor air flow (220) past a particle sensor (230).

8. The air filtration equipment (100, 900) according to claim 7, configured to operate the sensor fan (210) during a sensor clean-out time period (530) prior to determining the particle sensor data during a measurement time period (540).

9. The air filtration equipment (100, 900) according to any previous claim, where the particle sensor arrangement (190) is configured to evaluate the particle concentration in the filtered air flow by determining a concentration of particles of size about 0,3 .m.

10. The air filtration equipment (100, 900) according to any previous claim, comprising a dust measurement chamber (400) with an inlet (410) and an outlet (420), where the particle sensor arrangement (190) is arranged in an internal volume (430) of the dust measurement chamber (400), where the inlet (410) comprises an actuator (440) arranged to open and to close the inlet (410), where dust is allowed to pass into the internal volume (430) when the inlet is open and at least partly prevented from passing into the internal volume (430) when the inlet (410) is closed.

11. The air filtration equipment (100, 900) according to claim 10, where air is allowed to pass into the internal volume (430) via an air filter (450) when the inlet (410) is closed.

12. The air filtration equipment (100, 900) according to claim 10 or 11 , where the outlet (420) comprises an actuator (460) arranged to open and to close the outlet (420).

13. The air filtration equipment (100, 900) according to any previous claim, comprising a pressure sensor (191) configured to measure an air pressure between the one or more air filters (110, 120, 125, 930, 960) and the fan (160), where the control unit (160) is configured to suspend detection of air filter leakage in case the measured air pressure fails to satisfy an air pressure acceptance criterion.

14. The air filtration equipment (100, 900) according to claim 13, where the air pressure acceptance criterion comprises an air pressure in a range from ambient air pressure to 1 kPa below ambient air pressure, and preferably an air pressure in a range from ambient air pressure to 650 Pa below ambient air pressure.

15. The air filtration equipment (100, 900) according to any previous claim, comprising a temperature sensor (192) configured to measure an operating temperature drift of the equipment (100, 900), where the control unit (160) is configured to suspend detection of air filter leakage in case the operating temperature drift fails to satisfy a temperature drift acceptance criterion.

16. The air filtration equipment (100, 900) according to any previous claim, comprising a plurality of particle sensors arranged interleaved with a plurality of air filters (110, 120, 125, 930, 960) of the air filtration equipment (100, 900), where the control unit (150) is arranged to determine which out of the plurality of air filters (110, 120, 125, 930, 960) that is associated with leakage based on a comparison of particle sensor data from the plurality of particle sensors.

17. The air filtration equipment (100, 900) according to claim 16, where the control unit (150) is arranged to determine which out of the plurality of air filters (110, 120, 125, 930, 960) that is intact, i.e., not associated with leakage, based on a comparison of particle sensor data from the plurality of particle sensors.

18. The air filtration equipment (100, 900) according to any previous claim, comprising a first gas sensor and a second gas sensor arranged upstream and downstream from an additional filter (125) of the equipment (100, 900) arranged to filter gas, respectively, where the control unit (150) is arranged to detect leakage in the additional filter (125) based on a comparison of sensor data from the first gas sensor and the second gas sensor.

19. The air filtration equipment (100, 900) according to claim 18, where the additional filter (125) is a filter for volatile organic and / or inorganic compounds such as an activated carbon filter.

20. The air filtration equipment (100, 900) according to claim 18 or 19, where the control unit (150) is arranged to determine that the additional filter (125) of the air filtration equipment (100, 900) is intact, i.e., not associated with leakage, based on a comparison of sensor data from the first gas sensor and the second gas sensor.

21. The air filtration equipment (100, 900) according to any of claim 18-20, where the control unit (150) is configured to determine a remaining filter capacity of the additional filter (125) based on the comparison of sensor data from the first gas sensor and the second gas sensor.

22. The air filtration equipment (100, 900) according to any of claim 18-21 , where the control unit (150) is configured to determine a remaining filter lifetime of the additional filter (125) based on the comparison of sensor data from the first gas sensor and the second gas sensor over a time period.

23. The air filtration equipment (100, 900) according to any previous claim, comprising the additional filter (125) arranged to filter gas and an image capturing device (126) or photovoltaic sensor arranged to capture an image of the additional filter (125), where the control unit (150) is configured to determine a remaining filter capacity of the additional filter (125) based on the captured image.

24. The air filtration equipment (100, 900) according to claim 23, where the control unit (150) is configured to determine a remaining filter lifetime of the additional filter (125) based on a comparison of two or more captured images over a time period.

25. The air filtration equipment (100, 900) according to any of claim 18-24, where the control unit (150) is arranged to trigger generation of a notification in case the filtering capacity of the additional filter (125) fails to satisfy an acceptance criterion.

26. The air filtration equipment (100) according to any previous claim, configurable in a fan mode of operation, where the control unit (150) is configured to suspend detection of air filter leakage when the air filtration equipment (100, 900) operates in the fan mode of operation.

27. The air filtration equipment (100, 900) according to any previous claim, where the particle sensor arrangement (190) comprises an intake air guide (1000) arranged to guide an air flow towards a sensor part of the particle sensor arrangement (190).

28. The air filtration equipment (100, 900) according to claim 27, where the particle sensor arrangement (190) comprises an exhaust air guide (1010) arranged to guide an air flow away from the sensor part of the particle sensor arrangement (190).

29. The air filtration equipment (100) according to any previous claim, where the air filtration equipment is an air cleaner (100) arranged to filter ambient air or a heavy- duty dust extractor (900) arranged to filter air in a particle laden suction air flow.

30. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensorarrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, where the control unit (150) is configured to evaluate particle concentration in the filtered air flow in a repeating pattern, where each repetition in the repeating pattern comprises a particle concentration measurement cycle (520) followed by a waiting time period (550).31 . Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, where the particle sensor arrangement (190) comprises a sensor fan (210) arranged to generate a sensor air flow (220) past a particle sensor (230), where the air filtration equipment (100, 900) is configured to operate the sensor fan (210) during a sensor clean-out time period (530) prior to determining the particle sensor data during a measurement time period (540).

32. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120,125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), the air filtration equipment (100, 900) comprising a dust measurement chamber (400) with an inlet (410) and an outlet (420), where the particle sensor arrangement (190) is arranged in an internal volume (430) of the dust measurement chamber (400), where the inlet (410) comprises an actuator (440) arranged to open and to close the inlet (410), where dust is allowed to pass into the internal volume (430) when the inlet is open and at least partly prevented from passing into the internal volume (430) when the inlet (410) is closed, where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion.

33. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, the air filtration equipment (100, 900) comprising a pressure sensor (191 ) configured to measure an air pressure between the one or more air filters (110, 120, 125, 930, 960) and the fan (160), where the control unit (160) is configured to suspend detection of air filter leakage in case the measured air pressure fails to satisfy an air pressure acceptance criterion. where the air pressure acceptance criterion comprises an air pressure in a range from ambient air pressure to 1 kPa below ambient air pressure, and preferably an air pressure in a range from ambient air pressure to 650 Pa below ambient air pressure.

34. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, the air filtration equipment (100, 900) comprising a temperature sensor configured to measure an operating temperature drift of the air filtration equipment (100, 900), where the control unit (160) is configured to suspend detection of air filter leakage in case the operating temperature drift fails to satisfy a temperature drift acceptance criterion.

35. Air filtration equipment (100, 900) comprising a (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the control unit (150) is configured to detect leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion, the air filtration equipment (100, 900) comprising a plurality of particle sensors arranged interleaved with a plurality of air filters (110, 120, 125, 930, 960) of the air filtration equipment (100, 900) , where the control unit (150) is arranged to determine which out of the plurality of air filters (110, 120, 125, 930, 960) that is associated with leakage based on a comparison of particle sensor data from the plurality of particle sensors.

36. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), a control unit (150), and a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) further comprising a first gas sensor (1110) and a second gas sensor (1120) arranged upstream and downstream from a gas filter (125) of the air filtration equipment (100, 900), where the control unit (150) is arranged to detect leakage in the gas filter (125) based on a comparison of sensor data from the first gas sensor and the second gas sensor.

37. The air filtration equipment (100, 900) according to claim 36, where the gas filter (125) is a filter for volatile organic or inorganic compounds such as an activated carbon filter.

38. The air filtration equipment (100, 900) according to claim 36 or 37, where the control unit (150) is arranged to determine that the gas filter (125) of the air filtration equipment (100, 900) is intact, i.e., not associated with leakage, based on a comparison of sensor data from the first gas sensor and the second gas sensor.

39. The air filtration equipment (100, 900) according to any of claim 36-38, where the control unit (150) is configured to determine a remaining filter capacity of the gas filter (125) based on the comparison of sensor data from the first gas sensor (1110) and the second gas sensor (1120).

40. The air filtration equipment (100, 900) according to any of claim 36-39, where the control unit (150) is configured to determine a remaining filter lifetime of the gas filter (125) based on the comparison of sensor data from the first gas sensor and the second gas sensor over a time period.

41. The air filtration equipment (100, 900) according to any previous claim, comprising the additional filter (125) and an image capturing device (126) arranged to capture an image of the gas filter (125), where the control unit (150) is configured to determine a remaining filter capacity of the gas filter (125) based on the captured image.

42. The air filtration equipment (100, 900) according to claim 41 , where the control unit (150) is configured to determine a remaining filter lifetime of the additional filter (125) based on a comparison of two or more captured images over a time period.

43. The air filtration equipment (100, 900) according to any of claim 41 -42, where the control unit (150) is arranged to trigger generation of a notification in case the filtering capacity of the gas filter (125) fails to satisfy an acceptance criterion.

44. Air filtration equipment (100, 900) comprising a body (101 ) arranged to support one or more air filters (110, 120, 125, 930, 960), the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through the one or more air filters (110, 120, 125, 930, 960), a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, and a control unit (150) arranged to receive particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), where the fan (160) is arranged in a fan housing (1030), where the particle sensor arrangement (190) comprises an intake air guide (1000) arranged in connection to the fan housing (1030) to guide an air flow towards a sensor part of the particle sensor arrangement (190).

45. The air filtration equipment (100, 900) according to claim 44, where the particle sensor arrangement (190) comprises an exhaust air guide (1010) arranged to guide an air flow away from the sensor part of the particle sensor arrangement (190).

46. A computer implemented method, performed by a control unit (150) in air filtration equipment (100, 900) , the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through one or more air filters (110, 120, 125, 930, 960) of the air filtration equipment (100, 900) , and a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, the method comprising obtaining (Sa1) particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190), and detecting (Sa2) leakage in at least one air filter out of the one or more air filters (110, 120, 125, 930, 960) in case the particle concentration in the filtered air flow fails to satisfy an acceptance criterion,where detection of filter leakage by the control unit (150) is conditioned on that a startup time period (510) has passed from activation of the air filtration equipment (100, 900) .

47. A computer implemented method, performed by a control unit (150) in air filtration equipment (100, 900) , the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through one or more air filters (110, 120, 125, 930, 960) of the air filtration equipment (100, 900) , and a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, the method comprising, repeatedly, obtaining (Sb1) particle sensor data related to the particle concentration in the filtered air flow from the particle sensor arrangement (190) during a particle concentration measurement cycle (520), followed by waiting (Sb2) during a waiting time period (550).

48. A computer implemented method, performed by a control unit (150) in air filtration equipment (100, 900) , the air filtration equipment (100, 900) comprising a fan (160) arranged to generate an air flow through one or more air filters (110, 120, 125, 930, 960) of the air filtration equipment (100, 900) , and a particle sensor arrangement (190) arranged downstream from the one or more air filters (110, 120, 125, 930, 960) to evaluate a particle concentration in the filtered air flow, where the particle sensor arrangement (190) comprises a sensor fan (210) arranged to generate a sensor air flow (220) past a particle sensor (230), the method comprising, repeatedly, operating (Sc1) the sensor fan (210) during a sensor clean-out time period (530), followed by obtaining (Sc2) particle sensor data related to a particle concentration in the filtered air flow from the particle sensor arrangement (190).

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