Increased suction power in a suction smoke detector (ASD) to reduce transport time from a detected minimum signal level without issuing an interruption message.

Description

[0001] The invention relates to a method for operating an aspirating smoke detector, to such an aspirating smoke detector, and to a computer program product for implementing the inventive operating method. Such aspirating smoke detectors or aspirating fire detectors are also referred to in technical terms as ASDs (for aspirated smoke detectors).

[0002] In the method, the aspirating smoke detector is designed to detect a fire in a room to be monitored and to issue a fire alarm in the event of a detected fire, typically to a fire alarm control panel (FAC). Room air is sucked in by means of an aspirating smoke detector's intake unit via an intake pipe of the aspirating smoke detector provided with intake openings for smoke or fire gas to be detected, and is fed to a fire detector unit of the aspirating smoke detector for the metrological determination of a signal level of a fire parameter. The intake capacity of the intake unit is set to a nominal airflow value for normal operation, i.e., to a nominal airflow value intended for normal operation, to generate an airflow through the intake pipe.Finally, the suction power is increased from a minimum signal level value in order to shorten the transport time of sucked-in room air with smoke and / or fire gas through the suction pipe to the fire detection unit.

[0003] The aspirating smoke detector considered here comprises at least one fire detector unit for the metrological determination of a signal level of a fire characteristic, an aspiration unit, a power control unit for adjusting the aspiration power of the aspiration unit, and an aspiration pipe connected to the aspiration unit and provided with aspiration openings for aspirating room air containing smoke and / or fire gas to be detected. Furthermore, the aspirating smoke detector comprises an air flow meter, in particular a flow meter, for detecting an air flow of the aspirated room air, as well as an electronic control unit connected to the fire detector unit, the air flow meter, and the power control unit.The latter is designed to adjust the intake power of the intake unit to a nominal airflow value for normal operation using the power control unit, to increase the intake power from a minimum signal level using the power control unit to shorten the transport time, and to issue a fire alarm in the event of a fire being detected. The intake unit and the fire detector unit typically form a single unit.

[0004] Such a method and such an aspirating smoke detector are known from EP 2 244 236 A1. By increasing the fan speed and thus increasing the suction power, the transport time of the sucked-in room air with smoke through the suction pipe to the fire detection unit is shortened. This enables faster fire detection.

[0005] From the applicant's EP 2 407 946 A1, a method and a corresponding aspirating smoke detector for detecting blockages and interruptions in a pipe system are known. Air is drawn in via the pipe system from rooms and facilities to be monitored by a fan and monitored for fire characteristics. The air flow of at least a portion of the drawn-in air and the air temperature are measured. A blockage alarm is issued if the air flow falls below a predefined lower limit, and / or an interruption alarm is issued if the air flow exceeds a predefined upper limit. The fan speed increases as the air temperature increases and decreases as the air temperature decreases.

[0006] «Air flow» is the air volume flow V̇ or the air mass flow m It is therefore a time-dependent physical quantity. V̇ and air mass flow m are according to the physical relationship m = ρ·V̇ linked to each other via the density ρ.

[0007] "Normal operation" refers to normal, fire-free or smoke-free operation. This occurs, for example, after commissioning or after maintenance of an aspirating smoke detector.

[0008] The term “intake pipe” generally refers to a pipe system or a hose system. The intake pipe can comprise a single pipe, preferably made of plastic, or several partial pipes that are split, for example, by means of a pipe distributor. The intake pipe typically has a circular cross-section with a diameter in the range of 1 cm to 5 cm, preferably in the range of 2 cm to 3 cm. In particular, the intake pipe has a minimum pipe length of 30 m, preferably 50 m. A plurality of intake openings are present or incorporated along the intake pipe. They can be arranged at equal distances along the intake pipe, for example at a distance of 4 m to 8 m.

[0009] The signal level of a fire parameter to be determined metrologically is typically a concentration level or a concentration value of detected smoke or of a detected fire gas as a possible fire parameter. Smoke contains smoke particles of different particle sizes, which are also referred to as smoke aerosols. A typical fire gas is, for example, carbon monoxide or ammonia. The fire detector unit can have an optical detector unit, e.g. one based on the scattered light principle or the transmitted light principle, or a gas sensor sensitive to fire gases, such as a CO gas sensor. The minimum signal level value is dimensioned in particular so that there is a sufficiently high probability of a possible fire event, i.e. is significant for a possible fire event.The determination of the minimum signal level value can be based on empirical values ​​from a similar fire monitoring environment or can be carried out using measurement technology through an on-site fire test.

[0010] The signal level of a fire parameter to be determined by measurement is typically a concentration level or a concentration value of detected smoke or of a detected fire gas as a possible fire parameter. The minimum signal level value is particularly dimensioned such that there is a sufficiently high probability of a possible fire event, i.e. is significant for a possible fire event. The intake unit - typically a fan - and the fire detector unit are usually, but not necessarily, housed in a common housing as a structural unit. Viewed in the direction of flow, the intake unit can be located upstream or downstream of the fire detector unit. The fire detector unit can have an optical detector unit based on the scattered light or transmitted light principle and / or a gas sensor unit for fire gases.

[0011] Aspirating smoke detectors usually have a fan (aspirator). This extracts air samples from rooms via an intake pipe and feeds them to a fire detection unit. The intake pipes can extend over several hundred meters. Therefore, sucked-in smoke must be detected along their entire length to the fire detection unit. The time required for this is also referred to as dead time or transport time. For long intake pipes, the transport time can be in the range of minutes. For example, the maximum transport time for a pipe length of 200 m, an average flow velocity of 1 m / s, and smoke intake at a pipe end remote from the fire detection unit is 200 seconds.

[0012] Typically, an ASD planner calculates the key parameters to ensure that an aspirating smoke detector complies with the relevant standards, such as the European standard EN 54-20, in this case in the version valid at the time of this patent application from February 2009, or the North American standard UL268, preferably from the 6th or 7th edition. Various parameters play a role here, such as the pipe length, the room size, the number of aspirating openings, the aspirating pressure and the sensitivity of the fire detector unit. Various software-supported planning tools are available for the technical design of an aspirating smoke detector, such as the ASYST planning tool from Siemens. Once the parameters have been determined, a technician assembles the aspirating pipe, drills aspirating openings in the form of holes in the aspirating pipe and configures the fire detector unit according to the specifications.

[0013] Typically, the fan's intake power is also adjusted via the set speed in order to set an airflow with a nominal airflow value through the intake pipe. This speed then remains constant in smoke- or fire-free normal operation over the lifetime of the detector. In this normal operation, an aspirating smoke detector is therefore parameterized with a low fan speed in order to extend its service life and to minimize the noise level during intake. The reason for the static setting is to detect interruptions with a corresponding increase in airflow, or to detect blockages of the intake openings due to dirt with a corresponding decrease in airflow over the course of the operating time of the aspirating smoke detector. As soon as the airflow deviates by ± 20% from the nominal airflow value, e.g. according to the aforementioned EN 54-20, the aspirating smoke detector must issue a fault within a time period of 300 seconds specified in the standard.The UL268 standard, preferably from the 6th or 7th edition, specifies 90 seconds instead of the aforementioned 300 seconds. The nominal airflow value, measured in liters per second or liters per minute, is typically set during commissioning of an aspirating smoke detector.

[0014] Based on the aforementioned EP 2 407 946 A1, it is an object of the present invention to provide an improved method for operating an aspirating smoke detector.

[0015] It is a further object of the invention to provide a more reliable method for operating an aspirating smoke detector.

[0016] A further object of the invention is to provide an improved aspirating smoke detector. Finally, a further object of the invention is to provide an aspirating smoke detector that operates more reliably.

[0017] The object of the invention is achieved by the subject matter of the independent patent claims. Advantageous process variants and embodiments of the present invention are specified in the dependent claims.

[0018] According to the invention, an interruption message is issued for the process during fire-free or smoke-free normal operation if the air flow exceeds an upper limit for a minimum period of time. Irrespective of this, the intake power is increased from the minimum signal level value, i.e., when the minimum signal level value is exceeded, particularly to shorten the transport time, only for a period of time shorter than the minimum period during which the air flow exceeds the upper limit.

[0019] In other words, in order to shorten the transport time, the suction power is increased only within the minimum period so that the air flow exceeds the upper limit.

[0020] The targeted, temporary increase in the aspirating power advantageously prevents the generation of false interruption signals, in addition to enabling faster fire detection. This avoids unnecessary inspection of the aspirating smoke detector by a service technician. Nevertheless, the method according to the invention does not impair the monitoring of the aspirating smoke detector for interruption and blockage, which is prescribed in the exemplary standard described above and operates independently of the fire detection function.

[0021] With the return to normal operation, the noise development caused by the increased suction power and the mechanical overload of the aspirating smoke detector, which shortens its service life, will decrease again.

[0022] If, in the method according to the invention, the intake power is increased in such a way that the air flow exceeds the nominal air flow value, for example, by 1.2 times to 5 times, preferably by 2 to 3 times, the interruption message is still not issued if this increase is limited in time to the minimum period from the time the upper limit value is exceeded.

[0023] In other words, the intake power of the intake unit is reduced before the end of the minimum period, particularly shortly before the end of the minimum period, such that the air flow falls below the upper limit again. The reduction in intake power occurs particularly within a period of 1 s to 20 s, preferably 5 s to 10 s, before the expiration of the minimum period. This resets a timer in the control system of the aspirating smoke detector. The intake power can then be increased again above the upper limit without the interruption message being issued.

[0024] According to a further process variant, the suction power is only increased for a period of time less than the minimum period during which the airflow exceeds the upper limit, namely when a warning message, in particular a caution or attention signal, is received from a higher-level fire alarm control panel or control center, for example via a detector or bus line that connects the higher-level fire alarm control panel or control center to the aspirating smoke detector. Alternatively, the connection between the aspirating smoke detector and the fire alarm control panel or control center can be wireless, for example via a WLAN, Bluetooth, or a mobile 3G, 4G, or 5G data connection. The aforementioned (data) connections can also be based on an internet protocol. The fire alarm control panel or control center can also be implemented as a cloud application in a cloud infrastructure.In this sense, the aspirating smoke detector can receive the warning message "via the cloud" from a higher-level cloud fire alarm control panel or cloud control center. The warning message is issued if, for example, at least one other aspirating smoke detector in the vicinity of this aspirating smoke detector has already reported a fire alarm or an impending fire, e.g., in the form of a pre-alarm, to the fire alarm control panel or control center. The local correlation increases the probability of an actual fire in the vicinity of the installed aspirating smoke detector. In this case, an "anticipatory" increase in the aspirating power is advantageous for the earliest possible fire detection.

[0025] According to another variant of the procedure, a blockage warning is issued if the air flow falls below a lower limit for a minimum period of time.

[0026] According to a further variant of the method, the upper limit for the air flow is set at 1.2 times the nominal air flow value. Alternatively or additionally, the lower limit for the air flow is set, in particular, at 0.8 times the nominal air flow value. Further alternatively or additionally, the minimum period is set, in particular, to a value in the range of 60 seconds to 600 seconds, preferably to a value of 90 seconds or 300 seconds, or to a value of 90 seconds ± 3 seconds or 300 seconds ± 3 seconds.

[0027] According to a particularly advantageous variant of the method, the upper and lower limit values ​​for the air flow in relation to the nominal air flow value as well as a duration value for the minimum period are specified by a national, regional or international standard, in particular by the European standard EN 54-20, preferably as of February 2009.

[0028] According to the invention, the object of the invention is achieved by an aspirating smoke detector in which the electronic control unit is also configured or programmed to issue an interruption message intended for normal operation if the detected airflow exceeds a predetermined upper limit for a minimum period of time. Furthermore, the control unit is configured or programmed to increase the intake power (by means of the power control unit) from the minimum signal level value, i.e., when the minimum signal level value is exceeded, only for a period of time shorter than the minimum period during which the airflow exceeds the upper limit.

[0029] In other words, the control unit is configured or programmed to increase the intake power from the minimum signal level value, i.e. when the minimum signal level value is exceeded, by means of the power control unit only within the minimum period of time in such a way that the set air flow exceeds the upper limit value.

[0030] By means of the targeted and time-limited increase in the suction power brought about by the control unit via the power control unit, it is advantageously achieved that, in addition to the faster possible fire detection by means of the fire detector unit, the output of a false interruption message is prevented.

[0031] With the return to normal operation, the noise development caused by the increased suction power and the mechanical overload of the aspirating smoke detector, which shortens its service life, will decrease again.

[0032] If, according to the aspirating smoke detector according to the invention, the intake power is increased in such a way that the air flow exceeds the nominal air flow value by, for example, 1.2 to 5 times, preferably by 2 to 3 times, the interruption message is still not issued if this increase is limited in time to the minimum period from the time the upper limit is exceeded. The reduction in the intake power occurs in particular in a period of 1 s to 20 s, preferably 5 s to 10 s, before the expiry of the minimum period. This resets a timer in the control system of the aspirating smoke detector. The control unit can also be configured to begin increasing the intake power above the upper limit again after the reduction in the intake power, without the interruption message being issued.

[0033] According to one embodiment of the aspirating smoke detector, the aspirating smoke detector has a communication interface connected to the control unit. The control unit is configured to increase the suction power of the aspirating unit to shorten the transport time upon receipt of a warning message from the communication interface, in particular a warning or attention signal. In other words, the control unit is configured or programmed in this case to increase the suction power only for a period of time less than the minimum period in which the air flow exceeds the upper limit. The communication interface can, for example, be a wired communication interface for connecting a detector or bus line that connects the higher-level fire control panel or control center to the aspirating smoke detector. Alternatively, the communication interface can be a wireless communication interface, such as, for example,a Wi-Fi, Bluetooth, or a mobile 3G, 4G, or 5G data interface. The aforementioned communication interface can be based on an internet protocol, for example.

[0034] According to one embodiment, the control unit is configured to reduce the intake power, particularly shortly before the end of the minimum period, by means of the power control unit, such that the air flow falls below the upper limit again. "Shortly before the minimum period" refers to a period of 1 s to 20 s, preferably 5 s to 10 s, before the expiration of the minimum period.

[0035] According to a further embodiment, the control unit of the aspirating smoke detector is configured or programmed to analyze and evaluate the signal level of the fire characteristic to determine whether or not a fire event has occurred. It is also configured or programmed to reduce the suction power of the suction unit after the analysis and evaluation have been completed, and regardless of the minimum period, such that the airflow falls below the upper limit again, in particular so that the airflow returns to the nominal airflow value. If no fire event is detected, the aspirating smoke detector returns to normal operation.

[0036] According to a further embodiment, the electronic control unit is configured or programmed to issue a blockage message if the detected air flow falls below a predetermined lower limit for a predetermined minimum period of time.

[0037] As described at the beginning, «air flow» refers to the air volume flow V̇ or the air mass flow m The latter are, according to the physical relationship m = ρ·V̇ are linked by the density ρ. The density ρ is, according to the physical relationship ρ = p R ƒ ⋅ T with the air pressure p, with the gas constant R f for the air and with the air temperature T. The density ρ is thus proportional to the air pressure p and inversely proportional to the air temperature T.

[0038] For the operating method according to the invention and for the aspirating smoke detector according to the invention, it can be assumed in principle that the density ρ is essentially constant during normal operation of the aspirating smoke detector, i.e., it changes by less than 3%, in particular by less than 2%. Such density changes therefore have no practical influence on the airflow monitoring for the aspirating smoke detector. The air volume flow can be measured, for example, using a vane anemometer as a flowmeter. The air volume flow can be determined from the measured average flow velocity multiplied by the known internal pipe cross-section.

[0039] Alternatively, the air volume flow can be measured using a thermal air flow sensor, such as a hot wire anemometer, whose output signal, however, is a measure of the air mass flow mIf no significant changes in the ambient temperature, air pressure or humidity in the sucked-in room air are to be expected, an uncompensated thermal airflow sensor can be used as a flow meter. In more demanding application environments for the aspirating smoke detector, such as with high fluctuations in the ambient temperature and / or air humidity, such a thermal airflow meter can comprise a compensation device, as described in the aforementioned EP 2 407 946 A1. To take into account a detected air temperature, a detected air pressure and / or a detected air humidity, the compensation device can have a temperature sensor and possibly a pressure sensor or humidity sensor. A thermal airflow sensor compensated in this way can therefore function as a flow meter. A corresponding temperature, air pressure or humidity sensor can orcan be integrated into the intake unit or into the thermal hot wire anemometer itself.

[0040] According to one embodiment, the electronic control unit has a non-volatile memory for data access to the upper and lower limit values, as well as to the nominal airflow value and the minimum period. The upper limit value is 1.2 times the stored nominal airflow value, and the lower limit value is 0.8 times the stored nominal airflow value. The minimum period is set, in particular, to a value in the range of 60 seconds to 600 seconds, preferably to a value of 90 seconds or 300 seconds, or to a value of 90 seconds ± 3 seconds or 300 seconds ± 3 seconds. The non-volatile memory is, for example, an EPROM.

[0041] Alternatively, the upper and lower limits and the minimum period may be specified in a national, regional or international standard, such as EN 54-20, preferably as of February 2009.

[0042] Finally, the suction unit of the aspirating smoke detector according to the invention can be a fan or ventilator whose suction power increases with increasing speed n of the fan.

[0043] The electronic control unit is preferably a microcontroller, which is usually present or required for the entire control of the aspirating smoke detector. Furthermore, the microcontroller can have one or more integrated A / D converters for the metrological recording of the previously described input variables, such as air volume flow, air mass flow, signal level, and, if applicable, air temperature, air pressure, and humidity. It can also have analog and / or digital input and output units (I / O) as well as communication interfaces for issuing a fire alarm, an interruption message, or a blockage message. The upper and lower limit values ​​for the air flow, the nominal air flow value, the minimum period, and the minimum signal level value can be stored in the microcontroller's non-volatile memory (EPROM).In addition, the power control unit and / or electronic components for signal conditioning or signal processing of the aforementioned input variables can already be integrated in the microcontroller.

[0044] The object of the invention is finally achieved by a computer program product for implementing the inventive operating method on an electronic control unit, in particular on a microcontroller, of an aspirating smoke detector. The electronic control unit comprises an electronic memory, such as a RAM or EPROM, for storing the computer program product as well as for storing the minimum signal level value and the nominal air flow value as operating parameters. Optionally, the upper limit value for the air flow, the lower limit value for the air flow, and / or the minimum period can be stored in the electronic memory as additional operating parameters.

[0045] The computer program product is, in particular, an electronic file that can be loaded into the electronic memory of the electronic control unit. The computer program product can be stored, for example, on an optical or magnetic storage medium, such as a CD, DVD, or Blu-ray disc, or on a magnetic hard disk. Alternatively, the computer program product can be stored on a memory stick, such as a USB stick. Finally, the computer program product can also be loaded, at least indirectly, into the electronic memory of the electronic control unit via an intranet or the internet as a download.

[0046] This means that the faster fire detection made possible by the invention can be advantageously “retrofitted” to already installed aspirating smoke detectors by updating the operating software of the electronic control unit.

[0047] The invention and advantageous embodiments of the present invention are explained using the following figures as examples. They show: FIG 1 an exemplary structure of an aspirating smoke detector in smoke-free normal operation, FIG 2 the example according to FIG 1 in the event of a detected fire, and FIG 3 shows an example of an aspirating smoke detector according to the invention.

[0048] FIG 1shows an example of the design of an aspirating smoke detector ASD in smoke-free normal operation. On the left, an aspirating / detector unit ADE is shown as a structural unit, to which an aspirating pipe R with a plurality of distributed aspirating openings OF is connected. The latter are usually holes drilled into the aspirating pipe R. The aspirating openings OF typically have a non-uniform cross-section in order to achieve essentially the same "hole sensitivity" for all aspirating openings OF. This means that in normal operation, each of the aspirating openings OF draws in approximately the same volume per unit of time. K denotes a calibration hole located at the right end of the pipe. The holes shown in the left part of the FIG 1The intake / detector unit ADE shown comprises an intake unit L in the form of a fan, such as a radial fan, and a fire detector unit DET arranged upstream in the direction of flow. v M denotes the average flow velocity. The air flow or air volume flow drawn in by the intake unit L corresponds to the volume per unit time of the product of the average flow velocity v M and the internal cross-section of the intake pipe R.

[0049] FIG 2 shows the example according to FIG 1in the event of a detected fire. Room air containing smoke to be detected is sucked in at an intake opening OF, symbolized by a flame symbol, and transported through the intake pipe R to the fire detection unit DET. The lightning symbol on the fire detection unit DET symbolizes a detected fire event. This is the case when a detection signal DL emitted by the fire detection unit DET exceeds a specified minimum detection level MIN. In the example of the FIG 2 It can be seen how the drawn-in room air fills a transport or pipe section ST with smoke. T denotes the corresponding transport time. The transport time T is the product of the average flow velocity v M and the indicated transport section ST. As described above, the transport time T can be up to several minutes.

[0050] FIG 3shows an example of an aspirating smoke detector ASD according to the invention. The functional structure of the aspirating / detector unit ADE is shown in detail. In the right-hand part of the aspirating / detector unit ADE, which is implemented as a structural unit, a pipe connection AN can be seen, to which the aspirating pipe R is connected. The aspirating / detector unit ADE itself comprises the fire detector unit DET for the metrological determination of the signal level DL of a fire parameter. In the present example, the latter is a smoke concentration level. The aspirating smoke detector ASD or the aspirating / detector unit ADE further comprises a power control unit DR, which is designed to set an aspirating power P of the aspirating unit L. In the present case, the aspirating unit L is a fan, the aspirating power P of which can be set by changing the fan speed n L. In addition, the aspirating smoke detector ASD orthe intake / detector unit ADE has an air flow meter SEN for detecting an air flow. V̇, m of the room air drawn in. The air flow is an air volume flow V̇ or an air mass flow Ṭ. The air flow meter SEN outputs a corresponding air flow measurement signal, which indicates the air volume flow V̇ or the air mass flow m represents.

[0051] Furthermore, the aspirating smoke detector ASD or the aspirating / detector unit ADE has an electronic control unit MC connected to the fire detector unit DET, the airflow meter SEN, and the power control unit DR. The latter is typically a microcontroller and is configured or programmed to adjust the aspirating power P of the aspirating unit L to a nominal airflow value NW for (smoke-free) normal operation using the power control unit DR. The adjustment of the aspirating power P can be implemented in the form of an open or closed control loop, based on a currently measured airflow volume. V̇ or air mass flow min comparison with the nominal air flow value NW stored in an electronic memory MEM of the control unit MC. The control unit MC is further configured to issue a fire alarm AL in the event of a fire being detected and to issue an interruption message U during normal operation if the detected air flow V̇, ṁ a specified upper limit V̇ +, m + for a minimum period of time ZR is exceeded. The fire alarm AL and, if applicable, the interruption message U and a blockage message V can be output via the electronic control unit MC, e.g., at a bus interface of the suction / detector unit ADE.

[0052] The control unit MC is also designed or programmed to increase the intake power P by means of the power control unit DR from a minimum signal level value MIN of the signal level DL, i.e. when the minimum signal level value SIG is exceeded, in order to shorten the transport time T of sucked-in room air with smoke and / or fire gas through the intake pipe R to the fire detector unit DET.

[0053] According to the invention, the electronic control unit MC is designed to increase the intake power P from the minimum signal level value MIN only for a period of time less than the minimum period ZR, in which the air flow V̇, ṁ the upper limit V̇ +, m+ In other words, the electronic control unit MC can be set up or programmed to reduce the intake power P by means of the power control unit DR (shortly) before reaching the end of the minimum period ZR in such a way that the air flow V̇, ṁ the upper limit V̇ +, m + again falls below.

[0054] In addition, the electronic control unit MC can be configured to issue a clogging message V if the detected air flow V̇, ṁ a specified lower limit V̇ -, m - falls below the ZR for a specified minimum period. This also falls below the limit V̇ -, m - can be stored in the electronic memory MEM for a computational comparison by the control unit MC.

[0055] Finally, a computer program product PRG as well as the minimum signal level value MIN and the nominal air flow value NW as operating parameters PAR, as well as, if applicable, the upper and lower limit V̇ +, m +; V̇-, ṁ- for the air flow V̇ , m and / or the minimum period ZR as additional operating parameters PAR are stored, preferably in a non-volatile manner, in the electronic memory MEM of the electronic control unit MC. The computer program product PRG is configured to carry out the operating method according to the invention on an electronic control unit MC, preferably on a processor-based microcontroller, of the aspirating smoke detector ASD. It comprises corresponding suitable program steps and program routines for operating, i.e., controlling and monitoring, the aspirating smoke detector ASD. List of reference symbols

[0056] ADE Intake / detector unit AL Fire alarm, alarm AN Pipe connection, nozzle ASD Intake smoke detector DET Fire detector unit DL Signal level DR Power control unit, driver KKalibration hole LAsuction unit, fan, pump MC Electronic control unit, microcontroller MEM Memory, electronic memory, EPROM MIN Minimum signal level n L Fan speed NW Nominal air flow value OF Intake opening, bore PAsuction power PAR Operating parameters RAsuction pipe, pipe system SEN Air volume meter, flow meter, air mass meter ST Transport distance T Transport time U Interruption message V Blockage message v M Average air flow velocity ZR Period m Air mass flow V̇ Air volume flow m +upper limit m -lower limit

Claims

1. Method for operating an aspirating smoke detector (ASD), wherein the aspirating smoke detector (ASD) is provided for detecting a fire in a space to be monitored and for outputting a fire alarm (AL) in the event of a detected fire, wherein ambient air is aspirated by means of a suction unit (L) of the aspirating smoke detector (ASD) via a suction pipe (R) of the aspirating smoke detector (ASD) provided with suction openings (OF) for smoke or combustion gas to be detected, and is fed to a fire detector unit (DET) of the aspirating smoke detector (ASD) for determination by measurement of a signal level (DL) of a fire characteristic variable, and wherein for normal operation, the suction power (P) of the suction unit (L) is set to generate an airflow (V̇, ṁ) through the suction pipe (R) to a nominal airflow value (NW), and wherein the suction power (P) is increased from a minimum signal level (MIN) of the signal level (DL) in order to shorten the transport time (T) of aspirated ambient air with smoke and / or combustion gas through the suction pipe (R) to the fire detector unit (DET), characterised in that - an interruption signal (U) provided for normal operation is output if the airflow (V̇, ṁ) exceeds an upper limit value ( V̇+, ṁ+) for a minimum period (ZR), and - in that regardless thereof, the suction power (P) from the minimum signal level value (MIN) is increased only for a timespan smaller than the minimum period (ZR) in which the airflow (V̇, ṁ) exceeds the upper limit value (V̇+, ṁ+).

2. Method according to claim 1, wherein the suction power (P) of the suction unit (L) is increased to shorten the transport time (T) when a warning signal, in particular a prewarning or alert signal is received from a higher-level fire alarm control panel or command centre.

3. Method according to claim 1 or 2, wherein the signal level (DL) of the fire characteristic variable is analysed and evaluated as to whether a fire event exists or not, and wherein the suction power (P) of the suction unit (L) is reduced after completion of the analysis and evaluation and independently of the minimum period (ZR) such that the airflow (V̇, ṁ) again falls below the upper limit value (V̇+, ṁ+), in particular, such that the airflow (V̇, ṁ) is set again to the nominal airflow value (NW).

4. Method according to one of the preceding claims, wherein a blockage signal (V) is output if the airflow (V̇, ṁ) falls below a lower limit value (V̇-, ṁ-) for a minimum period (ZR).

5. Method according to claim 4, wherein the upper limit value (V̇+, ṁ+) for the airflow (V̇, ṁ) is set to 1.2 times the nominal airflow value (NW), wherein the lower limit value (V̇-, ṁ-) for the airflow (V̇, ṁ) is set to 0.8 times the nominal airflow value (NW) and wherein the minimum period (ZR) is set to a duration of 90 seconds or 300 seconds.

6. Method according to claim 4, wherein the upper and lower limit value (V̇+, ṁ+; V̇-, ṁ-) for the airflow (V̇, ṁ) in relation to the nominal airflow value (NW) and a duration value for the minimum period (ZR) are set according to a national, regional or international standard, primarily the European standard EN 54-20, preferably the version dated February 2009 or the standard UL268, preferably from the 6th or 7th issue.

7. Aspirating smoke detector (ASD), which has at least - a fire detector unit (DET) for determination by measurement of a signal level (DL) of a fire characteristic variable, - a suction unit (L), - a power control unit (DR) for setting a suction power (P) of the suction unit (L), - a suction pipe (R) connected to the suction unit (L) having suction openings (OF) for aspirating ambient air with smoke and / or combustion gas that is to be detected, - an airflow meter (SEN), in particular a flow meter, for acquiring an airflow (V̇, ṁ) of the aspirated ambient air, and - an electronic control unit (MC) connected to the fire detector unit (DET), the airflow meter (SEN) and the power control unit (DR), configured to adjust the suction power (P) of the suction unit (L) by means of the power control unit (DR) to a nominal airflow value (NW) for normal operation, to increase the suction power (P) from a detected minimum signal level (MIN) by means of the power control unit (DR) to shorten the transport time (T) and to output a fire alarm (AL) in the event of a detected fire, characterised in that - the control unit (MC) is configured to output an interruption signal (U) provided for normal operation if the acquired airflow (V̇, ṁ) exceeds a predetermined upper limit value (V̇+, ṁ+) for a minimum period (ZR), and - in that the control unit (MC) is configured to increase the suction power (P) from the minimum signal level value (MIN) only for a timespan shorter than the minimum period (ZR) in which the airflow (V̇, ṁ) exceeds the upper limit value (V̇+ , ṁ+).

8. Aspirating smoke detector (ASD) according to claim 7, wherein the aspirating smoke detector (ASD) has a communication interface connected to the control unit (MC) and wherein the control unit (MC) is configured, in the case of the reception of a warning signal from the communication interface, in particular a prewarning or alert signal, to increase the suction power (P) of the suction unit (L) in order to shorten the transport time (T).

9. Aspirating smoke detector (ASD) according to claim 7 or 8, wherein the control unit (MC) is configured to reduce the suction power (P) by means of the power control unit (DR) shortly before reaching the end of the minimum period (ZR) such that the airflow (V̇, ṁ) again falls below the upper limit value (V̇+, ṁ+).

10. Aspirating smoke detector (ASD) according to one of claims 7 to 9, wherein the electronic control unit (MC) is configured to analyse the signal level (DL) of the fire characteristic variable and to evaluate whether a fire event exists or not, and is configured to reduce the suction power (P) of the suction unit (L) after completion of the analysis and evaluation and independently of the minimum period (ZR) such that the airflow (V̇, ṁ) again falls below the upper limit value (V̇+, ṁ+), in particular, such that the airflow (V̇, ṁ) is set again to the nominal airflow value (NW).

11. Aspirating smoke detector (ASD) according to one of preceding claims 7 to 10, wherein the electronic control unit (MC) is configured to output a blockage signal (V) if the acquired airflow (V̇, ṁ) falls below a predetermined lower limit value (V̇-, ṁ-) for a predetermined minimum period (ZR).

12. Aspirating smoke detector (ASD) according to claim 11, wherein for a data access to the upper and lower limit value ( V̇+, ṁ+; V̇-, ṁ-) and the nominal airflow value (NW) and the minimum period (ZR), the electronic control unit (MC) has a non-volatile memory store (MEM), wherein the upper limit value (V̇+, ṁ+) is 1.2 times and the lower limit value (V̇-,ṁ-) is 0.8 times the stored nominal airflow value (NW) and wherein the minimum period (ZR) has a duration of 90 seconds or 300 seconds.

13. Aspirating smoke detector (ASD) according to claim 11, wherein the electronic control unit (MC) has a non-volatile memory store for a data access to the upper and lower limit value (V̇+, ṁ+; V̇-, ṁ-) in relation to the nominal airflow value (NW) and the minimum period (ZR), wherein the upper and lower limit value (V̇+, ṁ+; V̇-, ṁ-) and the minimum period (ZR) are set according to a national, regional or international standard, in particular the European standard EN 54-20, preferably the version dated February 2009 or the standard UL268, preferably from the 6th or 7th issue.

14. Computer program product (PRG) for carrying out the operating method according to one of claims 1 to 6 on an electronic control unit (MC) of an aspirating smoke detector (ASD), wherein the electronic control unit (MC) has an electronic memory store (MEM) for storing the computer program product (PRG) and for storing the minimum signal level (MIN) and the nominal airflow value (NW) as operating parameters (PAR), and possibly for storing the upper limit value (V̇+, ṁ+ ) for the airflow (V̇, ṁ), the lower limit value (V̇-, ṁ-) for the airflow (V̇, ṁ), and / or the minimum period (ZR) as further operating parameters (PAR).