Fire Detection and Alarm Systems, How to Add a Fire Detection and Alarm System

Abstract

The fire detection and alarm system includes a kitchen exhaust hood having a plenum connected to an exhaust fan configured to ventilate convective heat and cooking smoke emitted from one or more cooking appliances located below the kitchen exhaust hood. A fire suppression system is operatively connected to the hood and positioned above the one or more cooking appliances and configured to be activated by one or more fusible links having a predetermined melt temperature. At least one temperature sensor is located within the plenum of the kitchen exhaust hood to provide temperature measurements to a control module. The control module is configured to generate a fire warning signal when the smoke temperature reaches a particular temperature threshold Tset for a period of time Tdur. Tset and the time Tdur are selected based on the melt temperature ratings of the fusible links.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 251,274, filed October 1, 2021, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Fire suppression systems are used in hoods installed over cookstoves and ranges primarily to deliver a flame retardant to cooking surfaces to stop grease fires when temperatures indicative of a fire are measured in the plenum or ducts of the hood. Existing fire suppression systems work by opening a mechanical valve to release a flame retardant from a pressurized storage container and throughflow passage when high temperatures are detected near a fusible link, causing the fusible link to melt.

[0003] Fusible links are temperature sensitive fire protection devices designed as part of a fire protection system. The system is activated when the ambient temperature rises to a point where the fusible link "breaks". Typically, the chemical composition of the link causes the link or a portion of it to melt. At that point, a valve is mechanically actuated or a cable is severed, activating a remote valve to release a pre-loaded fire protection device and limit the spread of the fire.

[0004] In various configurations, the fusible links hold two mechanical members together under tension. Typically, these mechanical members are connected to a cable that runs around the inside circumference of the fume hood, with the mechanical members held under tension by the fusible links. The cable is connected to a distribution mechanism that stores the extinguishing agent. Depending on the temperatures the fusible links are exposed to, one of the fusible links melts, releasing the two mechanical members held by the fusible links and releasing the tension on the cable. This triggers the distribution mechanism to release the extinguishing agent.

[0005] Fusible links are one of the simplest fire detection devices and therefore are considered to be reliable and are required by various building codes; however, selecting the correct fusible link for every installation can be difficult and selecting the wrong fusible link can result in premature release of extinguishing agent.

[0006] There are many types of fusible links, each with a different melting temperature. When selecting a fusible link, an installer is supposed to heat all the appliances under the hood, measure the temperature inside the hood, and select one or more fusible links based on the measured temperature. In practice, however, this is rarely done. Instead, an installer may simply install the highest temperature fusible link available, reducing the likelihood of the fire suppression system being activated. Such an installation may meet building codes, but does not improve safety. Thus, a better method for selecting the temperature of a fusible link is needed.

[0007] Additionally, activation of a fusible link fire suppression system would cause significant disruption in the kitchen. It would be desirable to have a warning prior to activation of the fusible link fire suppression system, providing an opportunity to mitigate or avoid a fire outbreak, and avoiding the destructive activation of the fire suppression system. Summary of the Invention

[0008] One or more embodiments of the disclosed subject matter provide systems, devices, and methods for selecting an appropriate fusible link, for providing advance warning prior to deployment of a fusible link fire suppression system, and for retrofitting exhaust hoods with a warning system that warns of a potential fire prior to activation of a fusible link fire suppression system.

[0009] Objects and advantages of embodiments of the disclosed subject matter will become apparent from the following description considered in conjunction with the accompanying drawings. [Brief description of the drawings]

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals represent like elements. The accompanying drawings are not necessarily drawn to scale. Some figures may be simplified by omitting certain features for the purpose of more clearly showing other underlying features. This omission of components in some figures does not necessarily indicate the presence or absence of a particular element in any of the exemplary embodiments, unless expressly disclosed in the corresponding description.

[0011] [Figure 1] FIG. 1 illustrates a kitchen with fire detection and suppression elements according to an embodiment of the disclosed subject matter.

[0012] [Diagram 2] FIG. 2 is a schematic perspective view of an exhaust hood system positioned above a cooking appliance and including a fire alarm and suppression control system, according to various embodiments of the subject matter of the present disclosure.

[0013] [Diagram 3] FIG. 3 is an upward view of a kitchen exhaust hood according to various embodiments of the disclosed subject matter.

[0014] [Figure 4] FIG. 4 illustrates an example of a fusible link assembly according to an embodiment of the disclosed subject matter.

[0015] [Diagram 5] FIG. 5 is a block diagram of an exemplary fire detection and alarm system according to various embodiments of the disclosed subject matter.

[0016] [Figure 6] FIG. 6 is a diagram illustrating an example implementation of a controller for use in embodiments of the disclosed subject matter.

[0017] [Figure 7] FIG. 7 illustrates an example method according to various embodiments of the disclosed subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 illustrates a kitchen space 128 with systems and devices according to an embodiment of the present disclosure. An exhaust fan 116 draws air and smoke through a duct 127 that connects to an exhaust plenum 124. A filter 126 is attached to the inlet of the exhaust plenum 124, which draws smoke through a recess 122 in an exhaust hood 121. There may be multiple plenums 124, filters 126, and ducts 127 in a variety of different arrangements, and this embodiment is merely exemplary. Various sensors are shown, as described below.

[0019] The cooking appliance may be one of many types, such as a grill, fryer, oven, pizza oven, etc., and is generally designated by the reference numeral 120. The cooking appliance may produce cooking fumes 165 that are exhausted through an exhaust hood 121. Each appliance 120 is typically positioned adjacent to one another with gaps between adjacent appliances. These gaps between the equipment tend to trap dirt, grease, old food, and many other debris that can cause a fire hazard.

[0020] A fire suppressant, such as a chemical suppressant, is stored in a pressurized container 180 or other suitable subsystem. The dispensing device 107 may include, for example, a spray nozzle 107A. Water sprinkler, dry suppressant, and gas suppressant may also be dispensed.

[0021] The commercial kitchen space 128 may also be provided with a fire sprinkler system 117 having a sprinkler head 117A, which may be coupled to a dispensing device 107 such that the fire sprinkler system 117 delivers a fire extinguishing agent via a spray nozzle (or nozzles) 107A.

[0022] The extinguishing system, whether from the pressurized container 180 and / or from the sprinkler system 117, may be configured to be actuated by a fusible link assembly 217 such that when heated above a predetermined temperature for a predetermined period of time, the extinguishing agent is released from the nozzle. As shown in FIG. 3, the system may include a cable 218 held in tension by the fusible link assembly 217.

[0023] 3, a view showing the inside of the exhaust hood 121 is shown, looking from the ground up towards the ceiling. Exhaust duct 127 is visible at the end of exhaust plenum section 124. In this example, cables 218 can be seen running around the exhaust hood 121. Four fusible link assemblies 217 are shown in this example. The number of fusible link assemblies may be selected depending on the kitchen appliances to be placed under the exhaust hood 121, such that each fusible link assembly 217 is vertically aligned with kitchen appliances that may be expected to reach high temperatures in the event of a fire condition.

[0024] As discussed above, the fusible link assemblies include fusible links 413 that would have been selected based on the particular kitchen configuration, although this is often not the case. As shown in Figure 3, a temperature sensor 104 is positioned proximate, such as within 5 cm, 10 cm, 15 cm, or 20 cm, of each fusible link assembly 217. Although not shown in Figure 3, each temperature sensor 104 is connected to the controller 100. Thus, temperature readings from proximate each fusible link assembly 217 can be taken continuously or at regular intervals.

[0025] The controller 100 may continuously or intermittently monitor one or more inputs ultimately derived from various sensors, examples of which are summarized in Figures 1 and 2. The sensors may include temperature sensors 104, 125, and 129. Various other types of temperature sensors may be employed in the embodiments disclosed throughout this application, including thermocouples, resistance temperature sensors, resistance temperature detectors (RTDs), quartz crystal thermometers, thermistors, or other types of temperature sensors. One or more temperature sensors 104 may be provided in the recess 122 of the exhaust hood 121. The temperature sensor (or sensors) 125 may be located at a location that allows measurement of the ambient temperature outside the duct 127 and / or the surface temperature of the material of the duct 127. The temperature sensor (or sensors) 127 may be located to measure the air temperature within the duct 127. In the embodiments, the various temperature sensors are analog thermistors, whose electrical resistance changes with temperature.

[0026] The multiple temperature sensors 104 may be distributed in a rectangular or hexagonal array over a two-dimensional field within the recess 122 of the exhaust hood 121. The locations shown in Figure 1 are for illustration only. As mentioned above, the temperature sensors 104 may be used to indicate slowly changing or fluctuating temperatures from which statistics can be derived and used for classification as indicative of a fire. Examples of temperature sensors with low thermal inertia include thermistors, as well as RTDs and thermocouples.

[0027] Radiation emissions, i.e., light energy in the thermal field, may be detected and used to determine fire detection and / or indicated non-fire conditions, as detected by other sensors. These sensors may further comprise one or more radiant temperature sensors, such as 132 positioned and oriented to detect the average temperature of an area (field of view or FOV) or a radiant sensor oriented toward the fusible link of the fire suppression system. There may be multiple radiant temperature sensors aimed at multiple areas or FOVs. For example, a radiant sensor shown at 132 is oriented toward a portion of the cooking surface of the appliance 120, while another radiant sensor 110 is positioned to detect a flame in the recess 122 of the exhaust hood 121. The FOV may be narrow or wide. In each embodiment, the FOV is selectable. The signal provided by the radiant temperature sensor 110 is a real-time instantaneous signal, and the controller may obtain information from an unsteady signal therefrom.

[0028] The radiant temperature of an area is spatially resolved by one or more infrared cameras 113 and combined by a controller to detect fires and other hazardous conditions.

[0029] An optical or infrared video imaging device 199 (e.g., video camera, CCD sensor, FLIR sensor, etc.) may be mounted to detect the emergence of fire or smoke containing hot water vapor from the plane of the hood. This video camera 199 may be selected based on a wide range of optical and near infrared frequencies. A recognition algorithm implemented by the control device 100 may recognize the escape of fire or smoke from the hood. Normally, smoke, and certainly fire, should not be visible from above the hood 121. Fire and hot smoke can be easily detected because flammable vapors expand under the hood and are forced to escape from the regulated exhaust. Moreover, by employing an image or video imaging device such as the camera 199 for this purpose, the amount of escaping gas can be quantified to a certain extent, if not to an extreme extent, in that the radiant temperature and area of ​​the projected part of the radiating plume can be quantified with the help of image processing.

[0030] In one method, the controller may delay output of a fire indication or control of an output effector, such as an alarm or fire suppression system, to allow time for an operator to input a manual override. According to a method embodiment encoded by the processor-executable instructions, the controller may provide a warning signal indicating that a provisional fire detection has occurred, thereby alerting an operator to the need for a control input to prevent an alarm or suppression output.

[0031] Video scene classification techniques using artificial intelligence (e.g. supervised learning) can be applied to recognize dangerous situations before a fire actually occurs. The system can monitor various sensors and fusible link fire suppression systems. If the fire suppression system is activated, the control device stores the circumstances that led to the activation for post-mortem analysis, making it part of a supervised learning dataset that can recognize and predict the occurrence of a fire.

[0032] By classifying the hazard, the controller can generate a warning using any of the disclosed mechanisms without necessarily or immediately activating a fire suppression system. For example, if an infrared image of a blob in a scene determines that the hot blob is at an increasing temperature toward a predefined oil flash point, and motion analysis of the scene indicates no activity, the image becomes a simple classification problem defined by explicit rules in a classifier or implemented using supervised learning. Such a scene is deemed to be indicative of a possible fire outbreak.

[0033] The control device 100 may be connected to a remote or mobile UI (user interface), such as a smartphone, by a communication module 167. The communication module 167 may be a network or Internet interface, such as a modem, or may comprise a router or a switch. The communication module 167 may be a transceiver, and the mobile UI may be a wireless terminal.

[0034] An emergency situation may be detected as a fire breaking out nearby. These signals may be combined with a text output on the user interface 103 explaining the meaning and type of warning and the action to be taken. Visual signal generators such as strobe lights 158 may be provided to output the signals simultaneously or alternately. Audible signal generators such as alarms, sirens, or speakers may also be provided and operatively connected to the system to output warnings when commanded by the controller 100.

[0035] 2 illustrates an exemplary exhaust ventilation system, comprising an exhaust hood 121 disposed above a number of cooking utensils 120 and in communication with an exhaust assembly (not shown) via an exhaust duct 127. The bottom opening of the exhaust hood 121 is generally rectangular, but may have any other desired shape. The walls of the hood 121 define an interior volume 285, also called a plenum, which communicates with a downwardly facing bottom opening 190 at the end of the hood 121 disposed above the number of cooking utensils 120. The interior volume 285 may further communicate with the exhaust assembly through the exhaust duct 127. The exhaust duct 127 may extend upward through the exhaust assembly to an external exhaust environment.

[0036] The exhaust assembly may include a motorized exhaust fan (not shown) that draws exhaust air generated by the cooking appliance 120 into the exhaust duct 127 and expels it to the exterior exhaust environment. When the exhaust fan motor is activated, an exhaust flow path is established between the cooking appliance 120 and the exterior exhaust environment. As air is pulled away from the cooking surface area, smoke, air contaminants, and other air particles are exhausted through the exhaust duct 127 and the exhaust assembly to the exterior ventilation environment. The exhaust ventilation system 150 may further include one or more pressure sensors 208 for measuring static pressure in the main exhaust duct, and the bottom opening 190 of the exhaust hood 121 may include a number of grease removal filters (not shown) to remove grease and smoke particles that enter the hood exhaust duct 127.

[0037] The exhaust ventilation system 150 may further include a control module 200, which preferably includes a programmable processor operatively coupled to and configured to receive data from a number of sensors, including the temperature sensor 104, detect a fire condition, output an alarm, and optionally activate a portion of a fire suppression system. The controller may also control the speed of a powered exhaust fan, which will regulate the exhaust flow rate in the system. The control module 200 is in communication with a speed control module, such as a variable frequency drive (VFD) for controlling the motor speed, and the powered exhaust fan with one or more powered balancing dampers (not shown) located proximate the exhaust duct 127.

[0038] The control module 200 is further configured to control activation and deactivation of the fire suppression mechanism 400 based on the temperature within the hood 121 in addition to or instead of a fusible link extinguishing system (e.g., 117 and 180 shown in FIG. 1). That is, the two extinguishing approaches can be combined, with the fusible link extinguishing system providing fail-safe extinguishing due to the physical properties of the fusible link 413, which necessarily melts at a certain high temperature. Meanwhile, the extinguishing system 400 can be controlled by the control module 200 to initiate extinguishing at a specific location, such as only a single appliance or only a single location on a cooking surface. This approach allows for localized and more finely tuned extinguishing while still providing the fail-safe capability of the fusible link system. This approach can reduce disruptions caused by the activation of a fusible link extinguishing system, which often requires the kitchen to be closed for extensive cleaning and the fusible link extinguishing system to be inspected and recommissioned before the kitchen can be reopened.

[0039] In addition to or instead of fire suppression control, the control module 200 may detect a fire condition and generate an alarm via a user interface attached to the exhaust hood 121 or via a remote device (e.g., via a network interface to a device carried by the user) to warn of the fire condition before the fusible link fire suppression system is activated.

[0040] The control module 200 can further control the exhaust fan speed and activation of the fire suppression mechanism 400 based on the output of a sensor 314 located on or within the exhaust duct 127 and an infrared (IR) radiation temperature sensor 312 positioned facing the top surface of each cooking utensil 120. In at least one embodiment, three IR sensors 312 are provided and positioned above the cooking utensils 120 such that each IR sensor 312 faces the cooking surface of the corresponding cooking utensil 120. However, any number and type of IR sensors 312 and any number of cooking utensils 120 may be used as long as the radiation temperature of each cooking surface is detected. The control module 200 communicates with the sensors 314 and 312 and identifies the status of the cooking utensils based on the sensor readings. The status of the cooking utensils 120 is determined based on the exhaust temperature and radiation temperature sensed using the multiple detectors.

[0041] It should be noted that the radiant temperature sensor may include one or more IR cameras and one or more optical cameras, which may be added to the radiant temperature sensor. One camera may generate a "color" channel of a video signal, allowing one video stream to show the temperature and brightness of multiple locations in real time. In fact, a single video camera detecting infrared color and light bands may replace all of the radiant temperature sensors 312. Combinations of optical and infrared signals are particularly useful. For example, a persistent infrared signal without a simultaneous optical signal may be classified by a controller as a hot grill, while the same infrared signal combined with a strong or fluctuating optical signal may be classified as a fire. Spatial information provided by the cameras may further aid in disambiguating the composite signal.

[0042] The images, optical and / or infrared, can be image processed to generate reduced dimensionality state vectors as inputs for training and recognizing fire and cooking events. Many examples of normal cooking and fire conditions can be used to train supervised learning algorithms, which may then be used to recognize and classify normal cooking and fire conditions, respectively.

[0043] However, any of the embodiments may be modified by including a fire control nozzle with a fusible link. In such an embodiment, the fusible link sprinkler head may have a parallel supply controlled by a control valve of the fire suppression system. In the event of a failure of the control system, the fusible link releases water from the parallel supply, spraying water at a heat source, possibly a fire.

[0044] The fire suppression mechanism 400 may include, store, and / or regulate the flow of fire suppression including any known fire retardant material source capable of extinguishing a fire. The fire suppression mechanism 400 may further include a section in communication with digital networks interconnecting other systems that control and / or display status information regarding fans, filters, lighting, ducts, cooking appliances, food ordering, billing, inventory, public address, and / or other components. For example, in addition to initiating a fire suppression process, signals may be generated over such networks to notify occupants and / or firefighting authorities of a detected fire condition.

[0045] Although the nozzles 107A are shown as separate elements, they may be integrated with the extinguishing mechanism 400. The illustrated structure may be one or more separate nozzles connected to the extinguishing mechanism 400 by a fluid flow path. The nozzles 107A may be strategically placed within the ventilation system 150 to extinguish a fire regardless of its source. For example, one or more nozzles 107A may be placed in the grease collection area and one or more nozzles 107A may be placed directly above the cooking utensil 120. Each nozzle 107A communicates directly with the extinguishing control of the extinguishing mechanism 400, and when the mechanism 400 is activated by the control module 200, a fire retardant is discharged from the nozzles 107A. The fire retardant may be any known fire extinguishing agent, such as, but not limited to, water, a liquid potassium salt solution, or the like.

[0046] The control module 200 may determine the cooking appliance state (AS) based on the output of the exhaust temperature sensor 314 and the IR radiation temperature sensor 312, and may vary the exhaust fan speed and the position of the electrically adjustable damper in response to the determined cooking appliance state (AS). The control module 200 may further activate a fire suppression mechanism 400 based on the detected appliance state.

[0047] 3, the fire suppression agent, such as a chemical suppressant, is stored in a pressurized container 180 or other suitable subsystem. The dispensing device 107 may include, for example, a spray nozzle 107A. Water sprinkler, dry suppressant, and gas suppressant may also be dispensed.

[0048] The commercial kitchen space 128 may also be provided with a fire sprinkler system 117 having a sprinkler head 117A, which may be coupled to a dispensing device 107 such that the fire sprinkler system 117 delivers a fire extinguishing agent via a spray nozzle (or nozzles) 107A.

[0049] In a particular embodiment, a single temperature sensor is placed on or directly above the kitchen appliance with the highest thermal characteristics that pose the greatest risk of fire, such as a hard oil fryer powered by a gas burner. As another example, the appliance is a solid fuel powered appliance such as a coal or wood fired oven. Placing the temperature sensor above such an appliance with the highest thermal characteristics can detect a temperature rise that may eventually melt the fusible laying as a fire suppression system is activated. Thus, strategic placement of the temperature sensor can provide early detection of this dangerous temperature condition.

[0050] In a particular embodiment, two temperature sensors are placed at two opposite ends of the plenum section (internal volume) of the exhaust hood above multiple cooking appliances. Using two temperature sensors spaced apart and placed at opposite ends of the plenum section as described above, the entire cooking area can be sensed and the temperature rise caused by all the appliances can be measured. As described above, the temperature sensors can measure the temperature rise and detect a situation that may eventually cause the fusible link to melt and release the extinguishing agent. Early detection of the temperature rise can allow for actions to be taken such as raising an alarm, activating a local fire suppression system to suppress a small localized fire, or powering the cooking appliances on and off.

[0051] The control module receives signals indicative of temperatures measured by a temperature sensor or sensors within the kitchen exhaust hood plane. The control module is specially configured and programmed to perform a methodology described in more detail below. Generally speaking, the control module monitors temperature measurements and generates a fire warning signal if the smoke temperature measured within the plenum exceeds a particular temperature threshold (Tset) for a period of time (Tdur). This allows the control module to effectively integrate the measurements of heat energy generated and compare them to the melting temperature of the fusible link or links used in the fire suppression system. As will be appreciated, there are many types of fusible links, which are differentiated by their melting temperature and the time they can withstand heat before melting. When a fusible link is subjected to heat of sufficient intensity for a sufficient period of time, the link will melt and the fire suppression system will be activated. The control module is configured and specially programmed based on the fusible link rating to predict when the link is at risk of melting before the link melts. This can be accomplished by monitoring one or more temperature measurements, as described above, and noting when and for how long the temperature measurements exceed a particular threshold temperature.

[0052] In one embodiment, the temperature rating, size, and material of the fusible link are used to define the maximum thermal load that the fusible link can withstand before failing (i.e., melting). The control module monitors the temperature signals provided by one or more temperature sensors and the duration of various temperature readings to calculate the current drawn and the cumulative load. In this manner, the control module can predict that the fusible link is about to fail before an actual failure occurs.

[0053] 4, an exemplary fusible link assembly 217 is shown in detail. As shown, two articulated arms 411 are connected at a pivot point 412 and are pulled apart by a cable 218. A fusible link member 413 holds the two articulated arms in position. If the fusible link member 413 melts or structurally fails at a temperature close to the fusible link member 413, the tension in the cable 218 will pull the connecting members apart, reducing tension across the cable. This will activate the fire suppression system and spray extinguishing agent from the nozzle 107A. In some embodiments, activation is mechanical, with the release of tension in the cable 218 resulting in the valve opening.

[0054] As shown in FIG. 4, the temperature sensor 104 is provided near the fusible link member 413, so that the system can measure the ambient temperature near the fusible link member 413 and detect the temperature just before the fire suppression system is actually activated. In some embodiments, the temperature sensor 104 is an analog temperature sensor. In some embodiments, the sensor 104 is located less than 5 cm away from the fusible link member 413. In some embodiments, the distance is less than 30 cm. In some embodiments, the distance between the temperature sensor 104 and the cooking utensil that is expected to generate the most heat under the exhaust hood is substantially the same as the distance between the link member 413 and that cooking utensil. This allows approximately the same amount of heat energy to reach the link 413 and the sensor 104, allowing a more accurate approximation of the temperature of the fusible link 413.

[0055] In one embodiment, two temperature sensors 104 are provided on either side of the exhaust hood 121. These two temperature sensors 104 are capable of detecting heat that can warn of an impending release of extinguishing agent.

[0056] FIG. 5 is a block diagram of an exemplary fire detection and alarm system according to the present disclosure. In some embodiments, the system can also control the exhaust flow rate using the same controls and sensors used for fire detection and alarm. In particular, the system 1500 includes a control module 100 (or 200) that connects to a sensor 1504 and a control output 1506. The control module 100 or 200 is also coupled to an alarm interface 1508, a fire suppression interface 1512, and an appliance communication interface 1516, as described above. The alarm interface 1508 is coupled to an alarm system 1510. The fire suppression interface 1512 is coupled to a fire suppression system 1514. The appliance communication interface 1516 is coupled to one or more appliances 1518, 1520. The appliance communication interface can power off, turn off, or reduce the power of the appliance in response to a fire alarm. In some embodiments, when a fire alarm condition is reached, the control module can output a warning via the alarm interface and can additionally or alternatively command one or more appliances to power off or reduce power output. This command may cause relays to operate to turn off power to electrically powered appliances and may turn off gas valves on the gas supply to gas powered appliances.

[0057] Additionally, the control module 100 can activate the fire suppression system 1514 to apply extinguishing agent locally to a specific area under the exhaust hood with minimal disruption to other areas under the hood. This is in contrast to fusible link extinguishing systems, which also exist as fail-safe systems and typically discharge extinguishing agent from multiple nozzles, even from nozzles that are not targeted to the actual source of a particular fire.

[0058] During operation, the control module 100 / 200 communicates with and exchanges information with the alarm system 1510, the fire suppression system 1514, and the appliances 1518-1520 to better monitor the fire situation. The control module 100 / 200 may also provide information to the various systems (1510-1520) to allow them to adjust their functions for a more effective operating environment. For example, the control module 100 / 200, via its sensors 1504, may detect a fire or condition that is about to trigger a fusible link fire suppression system and issue a notification to allow an operator to take steps to end the condition and prevent the fusible fire suppression system from triggering.

[0059] The control module 100 / 200 may also communicate this information to the alarm system 1510, the fire suppression system 1514, and the appliances 1518, 1520 so that each device or system can take appropriate action. In some embodiments, the appliances are powered off (cutting off the power and / or fuel source, such as gas or propane).

[0060] Referring to FIG. 6, a process according to an embodiment of the present disclosure is shown. The process may be used to determine whether a fire condition exists or is about to occur that may activate the fusible link. The threshold temperature Tmax is selected based on the rated temperature of the fusible link. In some embodiments, Tmax is equal to the rated temperature. In other embodiments, Tmax is 1, 2, 3, 4, or 5 degrees Fahrenheit below the rated temperature. If the temperature sensor 104 is placed near the fusible link member 413, the measured temperature reflects the temperature of the fusible link and can be used to predict whether the fusible link is about to melt or break.

[0061] Temperatures are measured by sensors 104 in S701 and stored in S703. Storing the measured temperatures allows for a historical record to be created showing temperature trends. Temperatures are stored along with metadata such as time of measurement, date, appliance status, and fume hood status (including exhaust flow rate). This data can be provided to an artificial intelligence system that can perform supervised learning based on the stored data to derive conditions that require warnings or other alerts.

[0062] In S705, the measured temperature is compared to Tmax as described above. If the measured temperature T exceeds Tmax, a fire warning may be generated in S707. In some embodiments, Tmax is compared to T multiple times over a period of time to effectively integrate the amount of thermal energy, and a warning is generated only if the amount of thermal energy for a particular period of time exceeds a threshold. This approach takes into account the physical properties of the fusible link 413 and recognizes that a variety of conditions may cause the link to melt. A short period of high temperature may melt the link, but a slight drop in temperature will cause the link to take a longer time to melt. Thus, the controller stores temperature measurements and is aware of these various conditions so that a warning can be generated before the link melts.

[0063] If the temperature does not exceed Tmax, then in S709 the total elapsed time over which the measurements were taken is compared to the period P. In some embodiments, P is 60 days, 45 days, 30 days, 14 days, 7 days, or 1 day. For example, if the period P is 30 days and T does not exceed Tmax, then it is determined that Tmax is set too high. Thus, in S711, the value of Tmax is updated to a lower value and the process continues. In effect, this allows the system to learn over time what is considered a normal temperature in the exhaust hood and set Tmax accordingly. If Tmax is then exceeded, then a warning is displayed in S707 as this is a strong indication of a possible fire.

[0064] Embodiments of the method, system, and computer program product for controlling exhaust flow rate may be implemented on a general purpose computer, a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an ASIC or other integrated circuit, a digital signal processor, hardwired electronic or logic circuitry such as discrete element circuits, a programmed logic device such as a PLD, PLA, FPGA, PAL, etc. In general, any process capable of implementing the functions or steps described herein may be used to implement embodiments of the method, system, or computer program product for controlling exhaust flow rate.

[0065] Additionally, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow may be readily implemented fully or partially in software, such as using object or object-oriented software development environments that provide portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow may be partially or fully implemented in hardware, for example using standard logic circuits or VLSI designs. Other hardware or software may be used to implement embodiments, depending on the speed and / or efficiency requirements of the system, the specific functionality, and / or the specific software or hardware system, microprocessor, or microcomputer system utilized. Embodiments of the methods, systems, and computer program products for controlling exhaust flow may be implemented in hardware and / or software using known or later developed systems or structures, devices, and / or software by those skilled in the applicable field from the functional descriptions provided herein and with a general foundational knowledge of computers, exhaust flow, and / or cooking appliance technology.

[0066] Additionally, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow may be implemented in software executing on a programmed general purpose computer, special purpose computer, microprocessor, etc. Additionally, the exhaust flow control methods of the present invention may be implemented as programs embedded in a personal computer, such as JAVA or CGI scripts, as resources residing on a server or graphics workstation, as routines embedded in a dedicated processing system, etc. The methods and systems may also be implemented by physically incorporating the method for controlling exhaust flow into software and / or hardware systems, such as the hardware and software systems of an exhaust hood and / or appliance.

[0067] Figure 7 illustrates an exemplary embodiment of the various control devices 100 and 200 described above embodied as a computing device 800. Figure 7 is a block diagram illustrating an example of a computing device 800 arranged to control a dual mode lighting fixture, a germicidal return grill, and / or an HVAC system in accordance with the present disclosure. In a very basic configuration 801, the computing device 800 typically includes one or more processors 810 and a system memory 820. A memory bus 830 may be used for communication between the processor 810 and the system memory 820.

[0068] Depending on the desired configuration, the processor 810 can be of any type, including but not limited to a microprocessor (μP), a microcontroller (μC), a digital signal processor (DSP), or any combination thereof. The processor 810 can include one or more levels of cache, such as a level 1 cache 811 and a level 2 cache 812, a processor core 813, and registers 814. The processor core 813 can include an arithmetic logic unit (ALU), a floating point unit (FPU), a digital signal processing core (DSP core), or any combination thereof. A memory controller 815 can also be used with the processor 810, or in some implementations, the memory controller 815 can be an internal part of the processor 810.

[0069] Depending on the desired configuration, the system memory 820 can be of any type including, but not limited to, volatile memory (such as RAM), non-volatile memory (such as ROM, flash memory, etc.), or any combination thereof. The system memory 820 typically comprises an operating system 821, one or more applications 822, and program data 824. The applications 822 comprise multi-pass processing algorithms 823 arranged to control the lighting fixtures and the overall system in accordance with the disclosed embodiments. The program data 824 comprises data 825 useful for controlling the dual mode lighting fixtures, germicidal return grills, and / or HVAC systems, as described further below. In some embodiments, the applications 822 can be arranged to cooperate with the program data 824 on the operating system 821. This basic configuration is illustrated in FIG. 7 by the components within the dashed box number 801.

[0070] The computing device 800 may have additional features or functions and additional interfaces to facilitate communication between the basic configuration 801 and any devices and interfaces required. For example, a bus / interface controller 840 may be used to facilitate communication between the basic configuration 801 and one or more data storage devices 850 via a storage interface bus 841. The data storage device 850 may be a removable storage device 851, a non-removable storage device 852, or a combination thereof. Examples of removable and non-removable storage devices include magnetic disk devices such as floppy disk drives and hard disk drives (HDDs), optical disk drives such as compact disk (CD) drives and digital versatile disk (DVD) drives, solid state drives (SSDs), tape drives, and the like. Examples of computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data.

[0071] System memory 820, removable storage 851, and non-removable storage 852 are all examples of computer storage media. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVDs) or other optical storage devices, magnetic cassettes, magnetic tapes, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by computing device 800. Any such computer storage media may be part of device 800.

[0072] The computing device 800 may also include an interface bus 842 for facilitating communication from various interface devices (e.g., output interfaces, peripheral interfaces, and communication interfaces) to the basic configuration 801 via the bus / interface controller 840. Examples of output devices 860 include a graphics processing unit 861 and an audio processing unit 862, which may be configured to communicate with various external devices, such as displays and speakers, via one or more A / V ports 863. Examples of peripheral interfaces 870 include a serial interface controller 871 or a parallel interface controller 872, which may be configured to communicate with external devices, such as input devices (e.g., keyboard, mouse, pen, voice input device, touch input device, etc.) or other peripheral devices (e.g., sensor 104, etc.), via one or more I / O ports 873. An example of a communication device 880 includes a network controller 881, which may be arranged to facilitate communication with one or more other computing devices 890 via network communication via one or more communication ports 882. A communication connection is one example of a communication medium. Communication media may typically be embodied by computer readable instructions, data structures, program modules or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and includes any information delivery media. A modulated data signal is a signal that has one or more characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media may include wired media such as a wired network or direct-wired connection, and acoustic, radio frequency (RF), infrared (IR) and other wireless media. As used herein, the term computer readable media may include both storage media and communication media.

[0073] Computing device 800 may be implemented as part of a small-form factor portable (or mobile) electronic device such as a mobile phone, a personal data assistant (PDA), a personal media player device, a wireless web watch device, a personal headset device, a specific application device, or a hybrid device having any of the above functionality. Computing device 800 may also be implemented as a personal computer, including laptop computers and configurations other than laptop computers.

[0074] There is little distinction between hardware and software implementations of aspects of a system, and the use of hardware or software is generally (but not always, as the choice between hardware and software can be critical in certain situations) a design choice that represents a trade-off between cost and efficiency. There are various means (hardware, software, firmware, etc.) for implementing the processes and / or systems and / or other techniques described herein, and preferred means will vary depending on the context in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are paramount, then a primarily hardware and / or firmware means may be selected. If flexibility is paramount, then a primarily software implementation may be selected. Yet alternatively, a combination of hardware, software, and / or firmware may be selected.

[0075] The foregoing detailed description has illustrated various embodiments of the devices and / or processes using block diagrams, flow charts, and / or examples. To the extent that such block diagrams, flow charts, and / or examples include one or more functions and / or operations, those skilled in the art will appreciate that each function and / or operation within such block diagrams, flow charts, or examples can be individually and / or collectively implemented by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, some portions of the subject matter described herein may be implemented via an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), or other integrated form. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein may be equivalently implemented, in whole or in part, in an integrated circuit, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as substantially any combination thereof, and that in light of this disclosure, designing circuitry and / or writing software and / or firmware code is within the skill of those of ordinary skill in the art. Furthermore, those skilled in the art will recognize that the mechanisms of the subject matter described herein may be distributed as a program product in a variety of forms, and that the exemplary embodiments of the subject matter described herein apply regardless of the particular type of signal-bearing medium used to actually effect the distribution. Examples of signal-bearing media include, but are not limited to, recordable media, such as floppy disks, hard disk drives, compact disks (CDs), digital video disks (DVDs), digital tape, computer memory, and transmission-type media, such as digital and / or analog communications media (e.g., fiber optic cables, wave guides, wired communications links, wireless communications links, and the like).

[0076] With respect to the use of substantially any plural and / or singular terminology herein, those skilled in the art can translate from the plural to the singular and / or from the singular to the plural as appropriate to the context and / or application. For clarity, the various singular / plural permutations may be explicitly described herein.

[0077] According to a first aspect of the disclosed subject matter, a fire detection and alarm system includes a kitchen exhaust hood having a plenum connected to an exhaust fan configured to ventilate convection heat and cooking smoke emitted from one or more cooking appliances located below the kitchen exhaust hood, a fire suppression system operatively connected to the hood and positioned above the one or more cooking appliances, the fire suppression system configured to be activated by one or more fusible links having a predetermined melting temperature to release a fire suppression agent, at least one temperature sensor located within the plenum of the kitchen exhaust hood, and a control module operatively connected to the at least one temperature sensor and receiving a signal indicative of a temperature measurement by the at least one temperature sensor, wherein the control module is configured to generate a fire warning signal when a smoke temperature reaches a particular temperature threshold Tset for a period of time Tdur, the temperature threshold Tset and the time Tdur being selected based on a melting temperature rating of at least one of the one or more fusible links.

[0078] According to a variant, the fire detection and alarm system further comprises the one or more cooking appliances installed under the kitchen exhaust hood. According to a further variant, the fire detection and alarm system comprises two temperature sensors located on either side of an exhaust collar at opposite ends of the plenum of the kitchen exhaust hood.

[0079] According to a further variant, the at least one temperature sensor is located directly above the cooking utensil having the highest thermal properties or fire risk.

[0080] According to a further variation, the predetermined temperature set point is lower than a predetermined fusible link temperature.

[0081] According to a further variant, the control module is arranged to record the temperature sensor readings over an extended period of time.

[0082] According to a further variation, said extended period of time is 5 days, 1 week, 2 weeks, 4 weeks, 1 month, 2 months, 3 months, 4 months, 5 months, or 6 months.

[0083] According to a further variant, the control module is configured to determine whether the predetermined fusible link temperature Tset has been exceeded during the extended period and to update the temperature Tset to a lower value representative of the highest temperature value measured during the extended period.

[0084] According to a further variant, the control module is configured to update the temperature Tset to Tmax-dT, where Tmax is the maximum recorded temperature and dT is a predetermined temperature range limit value.

[0085] According to a further variation, dT is less than or equal to 10 degrees Fahrenheit.

[0086] According to a further variation, the fire detection and alarm system comprises one or more thermal imaging sensors positioned under the kitchen exhaust hood and configured to monitor a surface temperature of the cooking appliance under the hood and provide an output signal to the control module.

[0087] According to a further variation, the control module determines whether to output a fire warning based on a temperature signal from the temperature sensor and an output signal provided by the one or more thermal image sensors.

[0088] According to a further variant, the thermal characteristics HS (surface temperature and pixel area) of the device are recorded over a long period of time (at least 30 days) to establish a typical HS pattern (baseline).

[0089] According to a further variation, the HS pattern is used to establish a historical baseline and detect anomalies that may cause a potential fire.

[0090] According to a further variation, image recognition algorithms are used to establish baseline characteristics and abnormalities.

[0091] According to a further variation of any of the above embodiments and variations, T and HS are recorded at the time of fire onset, and the fire characteristics are established as a combination of T and HS recorded in time.

[0092] According to a further variation of any of the above embodiments and variations, the deviation of the current values ​​of T and HS from the values ​​representative of the fire characteristics is used to calculate the fire danger.

[0093] According to a further variant of any of the above aspects and variants, a space temperature sensor Tr is used.

[0094] According to a further variation of any of the above embodiments and variations, Tr is used to offset the T reading if the annual variation of Tr exceeds 5°F.

[0095] According to a further variation of any of the above aspects and variations, a plurality of temperature sensors are used to engage the fire suppression system.

[0096] According to a second aspect of the disclosed subject matter, a method of identifying a fire hazard condition includes providing a kitchen exhaust hood having a plenum section and an exhaust duct connecting to the plenum section, the kitchen exhaust hood having a fire suppression system having a fusible link installed therein; installing at least one temperature sensor in the plenum section; providing a control module operatively connected to the at least one temperature sensor; receiving, in the control module, a signal representative of a temperature in the plenum section from the at least one temperature sensor; comparing the temperature in the plenum section to a temperature representative of a melting temperature of the fusible link; and outputting a warning signal from the control module in response to a result of the comparison.

[0097] According to a variant, said warning signal is provided to a communication module which communicates with a mobile user device.

[0098] According to a further variation, at least one of the fusible links has a melting temperature Tm, the temperature sensor is positioned within a distance D from at least one of the fusible links having a melting temperature Tm, and the result of the comparison indicates a fire hazard condition if the measured temperature is within 5 degrees of Tm and the distance D is 5 cm or less.

[0099] According to a further variation, at least one of the fusible links has a melting temperature Tm, the temperature sensor is positioned within a distance D from the at least one of the fusible links having a melting temperature Tm, and the result of the comparison indicates a fire hazard condition if the distance D is less than or equal to 5 cm and the measured temperature is within 5 degrees of Tm during a time Td.

[0100] According to a further variant, said times Td are summed over the sampling intervals until the total combined duration during the window period Tw exceeds a time Tmax.

[0101] According to further variations, Td is 30 seconds, 1 minute, 2 minutes, 3 minutes, or 5 minutes, and Tmax is 1 minute, 2 minutes, 3 minutes, 5 minutes, or 10 minutes.

[0102] According to a third aspect of the disclosed subject matter, a method for addressing a fire hazard condition in or under a ventilation hood includes providing a first fire suppression system in or under the ventilation hood having a fusible link actuation mechanism; providing a second fire suppression system in or under the ventilation hood having an actuation mechanism separate from the first fire suppression system; identifying the fire hazard condition; in response to the identification, outputting an alert perceptible by a user of the ventilation hood; determining whether a fire condition exists; and, in response to the determination, targeted activation of the second fire suppression system to extinguish only an area under the ventilation hood that is on fire.

[0103] According to a third aspect variant, in order to identify said fire danger situation, a method according to any of the first aspect variants is implemented.

[0104] According to a further variation of any of the above aspects and variations thereof, the method further comprises activating the first fire extinguishing system in response to a fusible link of the fusible link actuation mechanism melting or in response to a control signal from a controller of the second fire extinguishing system.

[0105] According to a fourth aspect of the disclosed subject matter, a method of adding a fire detection and alarm system to a kitchen exhaust hood with a fire suppression system comprises the steps of providing a kitchen exhaust hood comprising a plenum portion connected to an exhaust duct, a controller configured to at least control an exhaust flow rate through the exhaust duct, and a fire suppression system configured to release a fire suppression agent below the kitchen exhaust hood in response to detecting a fire condition, and configuring the controller to measure a temperature adjacent a fire sensor of the fire suppression system and output a fire hazard warning if the measured temperature exceeds a predetermined temperature Tset for a time period exceeding Tdur.

[0106] According to a variant, the extinguishing system comprises a fusible link configured to melt at a specified temperature and thus activate the extinguishing system.

[0107] According to further variations, the vicinity is closer than 50 cm, closer than 40 cm, closer than 30 cm, closer than 20 cm, closer than 10 cm, or closer than 5 cm.

[0108] According to a further variant, Tset is less than or equal to a specific melting temperature of a fusible link of said extinguishing system.

[0109] According to a further variant, Tset is equal to the specific melting temperature of a fusible link of said extinguishing system.

[0110] According to a further variant, Tset is equal to the specific melting temperature of the fusible link of the extinguishing system minus Tdelta.

[0111] According to further variations, Tdelta is 1 degree Fahrenheit, 2 degrees Fahrenheit, 3 degrees Fahrenheit, or 4 degrees Fahrenheit.

[0112] According to a further variant, the method comprises the step of installing at least one temperature sensor in the vicinity of at least one said fire sensor.

[0113] According to a further variant, two temperature sensors are placed at opposite ends of the plenum section.

[0114] According to a further variation, the method comprises the step of installing at least one radiation temperature sensor under the exhaust hood with a direct line of sight view of the fire sensors of the fire suppression system, the at least one radiation temperature sensor being oriented to measure the radiation temperature of at least one of the fire sensors.

[0115] According to a fifth aspect of the disclosed subject matter, a method for verifying operation of a fire suppression system includes providing a fire suppression system configured to release a fire suppression agent in response to detection of a fire, the fire suppression system having one or more fire detectors; monitoring the one or more fire detectors with one or more temperature sensors and outputting signals from the one or more temperature sensors to a control device; and generating a fire alarm signal by the control device in response to a temperature measured by the temperature sensors exceeding a threshold temperature Tset for a time Tdur.

[0116] According to a variant, the one or more fire detectors comprise a fusible link having a predetermined melting temperature.

[0117] According to a further variation, the method further comprises the step of generating an alarm indicative of a failure of the extinguishing system in response to the temperature measured by the temperature sensor exceeding the predetermined melting temperature without the extinguishing system releasing the extinguishing agent.

[0118] According to a sixth aspect of the disclosed subject matter, a kitchen ventilation system is provided having a primary fire suppression system and a secondary fire suppression system for controlling the kitchen ventilation system based on a measured temperature.

[0119] It is apparent that all of the explicitly described aspects and variations thereof may be combined to create further embodiments. Many alternatives, modifications, and variations are possible with the present disclosure. Features of each disclosed embodiment may be combined, rearranged, or omitted within the scope of the disclosure to create additional embodiments. Furthermore, certain features may be advantageously used without corresponding use of other features. Accordingly, applicants intend to embrace all such alternatives, modifications, equivalents, and variations that are within the spirit and scope of the present disclosure.

Claims

1. 1. A fire detection and alarm system comprising: a kitchen exhaust hood having a plenum connected to an exhaust fan, the exhaust fan configured to ventilate convection heat and cooking fumes emitted from one or more cooking appliances located below the kitchen exhaust hood; a fire suppression system operatively connected to the kitchen exhaust hood and positioned above the one or more cooking appliances, the fire suppression system configured to be activated by one or more fusible links having a predetermined melting temperature to release a fire extinguishing agent; at least one temperature sensor located within the plenum of the kitchen exhaust hood; a control module operatively connected to the at least one temperature sensor and configured to receive a signal indicative of a temperature measurement by the at least one temperature sensor; The control module is configured to: ｄｕｒ over a specific temperature threshold T ｓｅｔ configured to generate a fire warning signal when The temperature threshold T ｓｅｔ and the time T ｄｕｒ is selected based on a melt temperature rating of at least one of said one or more fusible links.

2. 10. The fire detection and alarm system of claim 1, comprising two temperature sensors located on opposite ends of the plenum section of the kitchen exhaust hood, on either side of an exhaust annulus.

3. 10. The fire detection and alarm system of claim 1, wherein the at least one temperature sensor is located directly above a cooking appliance having the highest thermal characteristics or fire hazard.

4. 10. The fire detection and alarm system of claim 1, wherein the predetermined temperature set point is less than a predetermined fusible link temperature.

5. the control module is configured to record readings of the temperature sensor over time; 2. The fire detection and alarm system of claim 1, wherein the extended period is 5 days, 1 week, 2 weeks, 4 weeks, 1 month, 2 months, 3 months, 4 months, 5 months, or 6 months.

6. The control module determines whether the predetermined fusible link temperature T ｓｅｔ and determining whether the temperature T has exceeded a lower value representing the maximum temperature value measured during the long period. ｓｅｔ 6. The fire detection and alarm system of claim 5, configured to update the

7. The control module determines the temperature T ｓｅｔ T ｍａｘ -dT, and T ｍａｘ 6. A fire detection and alarm system as claimed in claim 5, wherein ≈ is the maximum temperature recorded and dT is a predetermined temperature range limit.

8. one or more thermal image sensors disposed beneath the kitchen exhaust hood and configured to monitor a surface temperature of the cooking appliance beneath the hood and provide an output signal to the control module; 10. The fire detection and alarm system of claim 1, wherein the control module determines whether to output a fire alert based on the temperature signal from the temperature sensor and the output signal provided by the one or more thermal imaging sensors.

9. 9. The system of claim 8, wherein the thermal characteristics HS (including surface temperature and pixel area) of the appliance are recorded over a long period of time (at least 30 days) to establish a typical HS pattern.

10. The system described in claim 6, which uses thermal signature patterns to establish historical baselines and detect anomalies that may cause potential fires.

11. The system of claim 6 , wherein an image recognition algorithm is used to establish baseline characteristics and abnormalities.

12. The system of claim 9, wherein the temperature T and thermal signature HS are recorded at the time of fire occurrence, and the fire signature is established as a combination of the temperature T and thermal signature HS recorded within a time period.

13. A system as described in claim 12, which calculates the fire risk using the deviation between the current values of temperature T and thermal characteristic HS and the values representing the fire characteristic.

14. The annual fluctuation of the space temperature sensor Tr 2. The system of claim 1, wherein a space temperature sensor Tr is used to offset temperature T readings above 5 degrees Fahrenheit.

15. 1. A method of adding a fire detection and alarm system to a kitchen exhaust hood equipped with a fire suppression system, comprising: providing a kitchen exhaust hood comprising a plenum connected to an exhaust duct, a controller configured to at least control an exhaust flow rate through the exhaust duct, and a fire suppression system configured to release a fire extinguishing agent below the kitchen exhaust hood in response to detecting a fire condition; and configuring the controller to measure the temperature adjacent a fire sensor of the fire suppression system and to output a fire hazard warning if the measured temperature exceeds a predetermined temperature, Tset, for a period of time exceeding Tdur.

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