Patent Abstract:
A number of different approaches are described for minimizing or preventing false alarms. In one case, override panels are used such as locally near or in the protected space or remotely at a security desk, for example. These override panels are used to deactivate or block the generation of a fire alarm signal in the case where the occupants or a management personnel recognizes that the fire alarm signal should not be generated. In this way, an alarm verification step is included. In another aspect, additional, contextual information is used to characterize or adjust when fire alarm signals are generated. This contextual information can be generated from sources that are not typically used in the generation of the fire alarm signal but instead are based on other sources of the information concerning the protected space.

Full Description:
BACKGROUND OF THE INVENTION 
     Fire sensors such as smoke detectors and heat detectors are among the most effective devices for providing early warning of danger associated with fires. Nevertheless, because fire sensors typically provide highly reliable smoke detection at the earliest presence of fire, they are also susceptible to false alarms. Responding to false alarms wastes critical financial and equipment resources of emergency responders, places the safety of the emergency responders and that of citizens in the response path at risk, and can divert emergency responders away from actual emergencies. 
     False alarms are also costly to businesses. Businesses suffer productivity losses due to the downtime associated with false alarms. In addition, emergency responders such as fire departments are increasingly charging businesses for the cost associated with responding to false alarms. 
     Moreover, many individuals have become accustomed to false alarms. The nuisance associated with false alarms can cause individuals to ignore future fire alarms. As a result, adoption and use of fire sensors in settings such as residences and business premises is declining due to the high incidence of false alarms generated by smoke detectors in the premises. 
     Fire sensors are often wired to a building network system that includes a fire alarm control panel or monitoring system. When a fire sensor detects heat and/or smoke, the fire sensor sends an alarm signal indicative of fire, such as a smoke level or an alarm state, to the monitoring system. In response, the monitoring system issues a general fire alarm signal and contacts emergency responders via an emergency telephone network (e.g. 911), for example. 
     False alarms occur for a number of reasons. In one example, dirt and dust that has accumulated on or within the fire sensors can interfere with normal detector operation. This can occur in residential settings as well as in commercial or municipal settings. For example, dirt and dust caused from trains entering a train station can cause fire sensors installed on train platforms to register false alarms if the fire sensors are not regularly maintained. In another example, aging fire sensors that have not been replaced within the manufacturer&#39;s recommended replacement period (e.g. 10 years) can cause false alarms. In yet another example, the fire sensors are improperly situated near high humidity areas such as bathrooms, the high humidity of which can trigger false alarms. 
     In still another example of false alarms generated by fire sensors, a fire sensor installed in a kitchen area correctly detects a release of smoke from food items cooking in the kitchen area (e.g. bread in toaster, skillet on a stove). In many cases, an initial fire threat associated with food in a kitchen area detected by a fire sensor is a transitory threat that can usually be eliminated by an individual present in the kitchen. However, because the signal indicating the fire event has already been sent by the fire sensor to the monitoring system, the monitoring system issues the general fire alarm and contacts emergency responders to respond to the threat. 
     Traditional approaches to minimizing false alarms have typically focused on improving the capabilities of the fire sensors. Improvements to fire sensors include incorporating multiple sensors (e.g, optical, ionization) into the devices and by using advanced smoke detection algorithms. However, these improvements have not significantly reduced the number of false alarms. 
     SUMMARY OF THE INVENTION 
     Aspects of the present invention take a number of different approaches to minimizing or preventing false alarms. In one case, override panels are used, such as locally near or in the protected space or remotely at a security desk, for example. These override panels are used to deactivate or block the generation of a fire alarm signal in the case where the occupants or management personnel recognize that the fire alarm signal should not be generated. In this way, an alarm verification step is included. In another aspect, additional, contextual information is used to characterize or adjust when fire alarm signals are generated. This contextual information can be generated from sources that are not typically used in the generation of the fire alarm signal but instead are based on other sources of information concerning the protected space. 
     In general, according to one aspect, the invention features a fire detection system that comprises one or more fire sensors installed in a building for detecting indications of fire and generating alarm signals and one or more override panels that enable occupants of the building to generate override commands. A monitoring system generates a fire alarm in response to the alarm signals from the fire sensors and whether or not the override commands have been generated. 
     In embodiments, the override panels include an override panel located in a room of the building within which the fire sensors sending the alarm signals are also installed. Then, in response to the alarm signals from the fire sensors, the monitoring system generates a local alarm, and the monitoring system blocks generation of the fire alarm and clears the local alarm in response to receiving the override commands from the override panel prior to expiration of a local override delay. 
     Preferably, in response to information indicative of the presence or absence of occupants, the monitoring system determines whether to generate the local alarm, the generation of which is a precondition for the monitoring system generating the fire alarm. Motion detectors, for example, can generate the information indicative of the presence or absence of occupants. Alternatively, or in addition, one or more surveillance cameras can capture video data within the building and an image analytics system can then analyze the video data captured by the one or more surveillance cameras to generate the information indicative of the presence or absence of occupants. 
     The override panels can also include a security desk override panel located in a security office of the building, wherein in response to the alarm signals from the fire sensors, the monitoring system generates a local alarm and generates the fire alarm if the local alarm is not acknowledged at the security office prior to expiration of the acknowledgment delay. 
     In general, according to another aspect, the invention features a fire detection method that includes detecting indications of fire and generating alarm signals and enabling occupants of the building to generate override commands. Then, a fire alarm is generated if the override commands have been not been issued. 
     In general, according to another aspect, the invention features a fire detection system that includes one or more fire sensors for detecting indications of fire and generating alarm signals and one or more non-fire detecting devices for detecting contextual information with respect to the one or more fire sensors. A monitoring system then generates a fire alarm in response to the alarm signals from the fire sensors and the contextual information from the non-fire detecting devices. 
     The fire sensors can include heat detectors and smoke detectors, for example. In one implementation, the monitoring system creates dependencies from the contextual information from the non-fire detecting sensors and uses the dependencies to minimize generating false fire alarms. 
     In examples, the non-fire detecting devices include at least one surveillance camera for monitoring an environment of at least one of the fire sensors, and the system further includes an image analytics system for determining presence and/or absence of individuals in the environment of the at least one of the fire sensors; wherein the monitoring system uses the determined presence and/or absence of individuals in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     The non-fire detecting devices can also include at least one motion sensor that detects motion within an environment of at least one of the fire sensors; wherein the monitoring system uses the detected motion in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     Further, the non-fire detecting devices can include at least one power monitor that detects power consumption of electrical devices, e.g., appliances, located within an environment of at least one of the fire sensors; wherein the monitoring system uses the detected power consumption of the electrical devices in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     Further, the non-fire detecting devices can include at least one temperature monitor that detects ambient temperature levels of an environment of at least one of the fire sensors, wherein the monitoring system uses the ambient temperature levels in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     Further, the non-fire detecting devices can include at least one humidity monitor that detects humidity levels of an environment of at least one of the fire sensors, wherein the monitoring system uses the humidity levels in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     Still further, the non-fire detecting devices can include at least one manual pull station that sends a signal indicating activation of the manual pull station within an environment of at least one of the fire sensors, wherein the monitoring system uses the signal indicating activation of the manual pull station in the environment of the at least one of the fire sensors as the contextual information for determining whether to generate the fire alarm in response to the alarm signals from the at least one of the fire sensors. 
     In general, according to another aspect, the invention features a fire detection method that includes detecting indications of fire and generating alarm signals, detecting contextual information for one or more fire sensors from non-fire detecting devices, and generating a fire alarm in response to alarm signals from the fire sensors and the contextual information from the non-fire detecting devices. 
     The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
         FIG. 1  is a system block diagram showing a first embodiment of a fire detection and alarm system including fire sensors installed in an exemplary premises such as a residential or commercial building, where the system also includes override panels. 
         FIG. 2  is a flow diagram that shows a method of operation of the monitoring system for handling override signals from local override panels. 
         FIG. 3  is a flow diagram that shows a method of operation of the monitoring system for handling override signals from security desk override panels. 
         FIG. 4  is a system block diagram showing a second embodiment of a fire detection system with an event context system. 
         FIG. 5  shows a table of dependencies that the event context system creates from the contextual information received from the one or more non-fire sensor devices, and also shows pseudocode of an exemplary software action that references the dependencies, and where the event context system executes the exemplary software action for determining whether to generate the fire alarm in response to the alarm signals sent from the fire sensors. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Further, the singular forms and the articles “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms: includes, comprises, including and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, it will be understood that when an element, including component or subsystem, is referred to and/or shown as being connected or coupled to another element, it can be directly connected or coupled to the other element or intervening elements may be present. 
       FIG. 1  shows a first embodiment of a fire detection and alarm system  10  including fire sensors installed in a premises such as a residential or commercial building, where the system also includes override panels according to the principles of the present invention. 
     Shown are a set of rooms  52 ,  62 ,  72  in a residential building. In one example, the building is an apartment building. In other examples, however, the system  10  is deployed in nonresidential buildings such as office buildings that may have a kitchen or appliances in a breakroom, for example. 
     The first room  72  corresponds to a utility closet that includes parts of the system including the monitoring system. Also, access to a public network  23  is provided through networking devices potentially including routers or hubs. 
     Also shown is a second room  52  that potentially corresponds to a kitchen or breakroom within the building. As is common, this room may include a stove  32  and other electrical appliances such as a toaster  36  on the table  90 . 
     Finally, in another room  62 , a security desk  88  for possibly an apartment or commercial building is provided. Security personnel  102  may man this security desk  88 . 
     In each of these rooms  72 ,  52 ,  62  fire sensors such as heat detectors  21 - 1 ,  21 - 2  and smoke detectors  20 - 1 ,  20 - 2 ,  20 - 3  are installed. In addition, the residential room  52  may further include such other security, safety devices such as a motion detector  44 , a fire pull station  42 , and a surveillance camera  103 . 
     In the illustrated example, the components of the fire detection and alarm system are located within the utility closet or utility room  72 . This includes a monitoring system  120  such as a monitoring panel. It communicates with an emergency telephone network  24  so that it can automatically call the fire department in the case of a fire. Also, in the illustrated example, an image analytics system  128  is further provided. In different examples, this image analytics system  128  stores video from the surveillance camera  103 . It also preferably analyzes that video to determine whether rooms within the building are occupied, for example. 
     According to an aspect of the invention, occupants of the building can use the override panels  50 - 1 ,  50 - 2  to override a fire alarm. The occupants generate override signals via the override panels  50 - 1 ,  50 - 2  when the users know or have reason to know that a fire alarm instigated by fire sensors is false or transient and benign (e.g. a mere puff of smoke from a toaster). 
     In one example of its operation, the heat detector  21 - 2  in kitchen area  52  detects heat from a pot boiling  30  on a stove  32 . In response, the heat detector  21 - 2  or the smoke detector  20 - 1  send(s) alarm signal(s) indicative of fire to the monitoring system  120 , which activates a local alarm, in response. In one example, this local alarm is an audible signal that is generated by speaker  150  of the local override panel  50 - 1 , which is installed in the same room  52  from where the alarm signals originated. This local alarm need only be audible to the occupants in the kitchen  52  rather than the entire building. 
     As a result, a person in the kitchen hearing the local alarm will realize that it is due to the transitory heat condition caused by the boiling pot  30  and that there is no need for the generation of a building-wide fire alarm or a call to the fire department. In response, the person selects/depresses the override button  54  of the override panel  50 - 1  or otherwise signals the panel  50 - 1  such as by a voice recognition system in the kitchen area  52 . The monitoring system  120  receives the override signal sent by the local override panel  50 - 1 , and in response, clears the local alarm and blocks the triggering of the fire alarm by the monitoring system  120 . 
     In this way, a false alarm, the evacuation of the building, and potentially the issuing of a fire alarm signal to the local fire department are avoided. 
     In another implementation, the receipt of fire alarm signals from the smoke detector  20 - 1  or the heat detector  21 - 1  in room  52  or the detection of heat by the heat detector  21 - 1  or the smoke detector  20 - 3  in room  72  lead to the generation of a local alarm by the security desk override panel  50 - 2 . This allows the security personnel  102  at the security desk  88 , for example, to investigate the possibility of a fire in rooms  52  or  72 , for example, due to normal activities such as the boiling pot  30  or the toaster  36 . Here again, in the case of the detection of an indication of fire in the utility closet  72  or the kitchen  52 , a local alarm is generated at the security desk override panel  50 - 2  such as an audible alarm by its speaker  150 . 
     The generation of this local alarm allows the security personnel  102  to investigate the source of the alarm and then issue an override signal to the monitoring system  120  to avoid a false alarm, when appropriate. 
       FIG. 2  is a flow diagram that shows a method of operation of the monitoring system  120  for handling override signals from local override panels. 
     This shows how the monitoring system  120  determines whether to generate a fire alarm when the monitoring system  120  receives alarm signals sent by fire sensors  20 - 1 ,  20 - 2 ,  20 - 3 ,  21 - 1 , and/or  21 - 2  and/or information sent from non-fire detecting devices (e.g. motion detectors  44 , or surveillance cameras  103 ) and override signals sent from override panels  50 - 1 ,  50 - 2 , when the fire sensors, the non-fire detecting devices, and the override panel are located within the same room of a building (e.g. the kitchen) as the source of the alarm signals. 
     In more detail, in step  202 , the fire detection system is in its normal idle state, and remains in the state until an alarm signal is received in step  204 . This alarm signal would typically be generated by any one of the fire sensors  20 - 1 ,  20 - 2 ,  20 - 3 ,  21 - 1 , and/or  21 - 2 , in the illustrated example. 
     In step  206 , the fire detection system determines whether or not a manual pull station such as pull station  42  has been activated. In general, the activation of a manual pull station is determined by the system to be strong evidence of a potential fire and as a result the flow proceeds to the generation of a building or general alarm state in step  222 . 
     On the other hand, if a manual pull station has not been activated, the ID number of the activated fire sensor is sent to the monitoring system  120  to determine the location of the fire sensor. Specifically, the proximity between the override panel and the activated fire sensor is assessed. If a local override panel is not located in the same room as the room in which the activated fire sensor is located or also potentially a nearby room, then again, general building alarm state is initiated in step  222 . 
     On the other hand, if there is an available local override panel  50 - 1 ,  50 - 2  such as in the same room or a nearby room or in the same apartment or on the same floor as the activated fire sensor, then in step  212 , the system optionally determines whether or not people are detected in the room and/or a nearby room and/or in the same apartment and/or on the same floor as the activated fire sensor. If people are not determined to be in the same room as or otherwise nearby the override panel, then it does not make sense to wait for the activation of the override signal since no one is in proximity to activate the override panel  50 - 1 ,  50 - 2 . Thus, in this case, the fire alarm is generated. 
     On the other hand, if it is determined that people are in proximity to the override panel  50 - 1 , then the local alarm is generated in step  214  and a local override delay is performed. The justification is that if there is a local override panel  50 - 1 ,  50 - 2  local to the source of the alarm signals, and people are further present, then they should be notified that the fire detection system is in the process of potentially generating a fire alarm by generating the local alarm. The local alarm thus gives them an opportunity to override the generation of fire alarm. 
     From step  214 , processing takes one of two paths. If the local override is selected, such as by a user pressing override button  54  such as on the local override panel  50 - 1 , then the fire alarm is blocked in step  220 . On the other hand, if the override is not selected within the local override delay, which can be as short as a 10 seconds or as long as several minutes, then the general alarm state for the building is activated in step  222 . 
       FIG. 3  is a flow diagram that shows a method of operation of the monitoring system  120  for handling override signals from security desk override panels  50 - 2 . 
     This shows how the monitoring system  120  determines whether to generate the fire alarm when the override panel  50 - 2  is installed in a different room than the fire sensors that generated the alarm signals and the non-fire detecting devices. In the example, a desk override panel  50 - 2  is installed in a security office  62  that generates the override signals. 
     In steps  302  and  304 , the fire detection and alarm system  10  waits for the receipt of fire alarm signals such as from one of the fire sensors  20 - 1 ,  20 - 2 ,  20 - 3 ,  21 - 1 , and/or  21 - 2 . 
     If the fire alarm signals originate from a manual pull station as determined in step  306 , then the fire alarm is not blocked and a general building fire alarm is generated in step  330 . 
     On the other hand, if the fire alarm signal is not from a manual pull station then the record ID of the fire sensor sending the alarm signals is sent to the monitoring system  120  and its location is determined in step  308 . It is then determined if a security override panel is installed in step  310  and whether the sensor sending the alarm signals is subject to security desk override. If so, then a local desk alarm is generated in step  314  at the security desk override panel  50 - 2  and a local acknowledgment delay process is started in step  314 . 
     The process then circulates between steps  316  and  318 . Specifically, the monitoring system  120  in step  316  checks whether or not the security desk personnel have acknowledged the local alarm, which is generated by, for example, an audible signal from speaker  150  of the override panel  50 - 2 . The audible signal may further include a synthetically generated verbal description of the location of the alarm signals. 
     On the other hand, the monitoring system determines whether or not the security desk personnel have taken too long to acknowledge the local alarm in step  318 . If the security desk personnel do not acknowledge the local alarm, in for example 20 seconds to a minute by depressing the button  54  on the panel  50 - 2  or by verbally acknowledging the local alarm in the case of a voice recognition system, then the general fire alarm is generated in step  330 . On the other hand, if within the delay, the security desk personnel do acknowledge the local alarm as determined in step  316 , then a second override delay is started in step  320 . Specifically, this delay allows the security personnel to investigate the location that was the source of the alarm signals to determine whether or not a fire is actually present. 
     A dead man&#39;s switch-type delay is now initiated. That is, if the security desk override delay expires as determined in step  324 , then the general building fire alarm is generated in step  330 . This addresses the situation where the security personnel investigate the fire and learn that a fire is actually present and then become consumed with putting out the fire or assisting others, for example. In another situation, the security desk personnel could become overwhelmed by the fire. In such situations, then a fire alarm will be generated in step  330  at the expiration of the override delay as determined in step  324 . 
     On the other hand, if within the override delay, which can be as short as tens of seconds to as long as several minutes, the override signal is generated by the security personnel such as by depressing switch  54  on the security desk override panel  50 - 2 , then the fire alarm is blocked in step  326 . This addresses the situation where the security personnel investigate the location of the fire and discover that no fire is present. Then, they generate the override signal from the security desk override panel  50 - 2 , for example, or potentially some other override panel within the building to thereby block the generation of the fire alarm in step  326 . 
       FIG. 4  is a system block diagram showing a second embodiment of a fire detection system with an event context system. 
     In this embodiment, the event context system  122  of the monitoring system  120  receives alarm signals in response to detected fire conditions from the fire sensors  20 - 1 ,  20 - 3 ,  21 - 1 , and/or  21 - 2  and contextual information from one or more non-fire sensor devices. The non-fire detecting devices include surveillance cameras  103 - 1 ,  103 - 2 , motion detectors  44 , and manual pull stations  42 . In addition, the non-fire detecting devices in this embodiment include temperature monitors  74 , humidity monitors  75 , and power monitors  62 - 1 ,  62 - 2 , in examples. 
     The non-fire sensors  42 ,  44 ,  62 - 1 ,  62 - 2 ,  62 - 3 ,  74 ,  75 ,  103 - 1 ,  103 - 2  send contextual information associated with the environment of the fire sensors  20 - 1 ,  20 - 3 ,  21 - 1 , and/or  21 - 2 . In one example, the environment of the fire sensors includes a wiring closet  72  and a nearby room  52  within which the fire sensors are installed, where the fire sensors can detect conditions indicative of fire in both the wiring closet  72  and the nearby room  52 . In the same example, the contextual information is the determined presence or absence of individuals in the room  52  and in the wiring closet  72 . 
     In more detail, the wiring closet  72  in this example includes a temperature monitor  74  and potentially a surveillance camera  103 - 2 . Each of these non-fire detecting devices generates context information that is detected by the monitoring system  120 . 
     In a similar vein, other rooms within the building such as kitchen  52  further include additional non-fire detecting devices for generating context information for the monitoring system  120 . For example, the motion detector  44  detects motion such as people moving within the room  52 . The surveillance camera  103 - 1  captures images from the room which can then be analyzed by the image analytics system  128  or an analytics system incorporated within the camera. Further, a humidity monitor  75  monitors humidity within the room  52 . 
     In the illustrated example, power monitors  62 - 1 ,  62 - 2 ,  62 - 3  are further provided for circuit breaker panels  40  and or specific appliances  32 ,  36 , respectively. For example, the stove  32  has a power monitor  62 - 2 . Further, the toaster  36  has its own power monitor  62 - 3 . In addition or alternatively, a power monitor  62 - 1  is provided for the circuit breaker panel  40  that controls the electricity to the room  52 . 
     Each of these power monitors provides power consumption information back to the monitoring system  120 . Specifically, in the illustrated embodiment, the event context system  122  analyzes the contextual information provided by these non-fire detecting devices to determine whether or not a fire alarm signal should be generated. 
       FIG. 5  shows a table of dependencies that the event context system  122  applies to the contextual information received from the one or more non-fire sensor devices, and also shows pseudocode of an exemplary software action that references the dependencies, and where the event context system executes the exemplary software action for determining whether to generate the fire alarm in response to the alarm signal sent from the fire sensors. 
     This shows one implementation of the event context system for determining whether to generate the fire alarm in response to the alarm signal sent from the fire sensors  20 - 1 ,  20 - 2 ,  20 - 3 ,  21 - 1 , and/or  21 - 2 . In the implementation the monitoring system  120  generates a fire alarm when an alarm threshold is reached for any one of the fire sensors  20 - 1 ,  20 - 2 ,  20 - 3 ,  21 - 1 , and/or  21 - 2 . However, the sensitivity, specifically the alarm threshold, is adjusted based on the contextual information received from the non-fire detecting devices  42 ,  44 ,  62 - 1 ,  62 - 2 ,  62 - 3 ,  74 ,  75 ,  103 - 1 ,  103 - 2 . 
     In the example, the event context system adjusts the alarm threshold by creating dependencies from the contextual information, where the dependencies are associated with states of the non-fire detecting devices and aspects of contextual information they provide, in examples. The event context system then references the dependencies in software actions to determine whether to generate the fire alarm in response to the alarm signals sent from the fire sensors. 
     In the exemplary software action, the alarm threshold is initially initialized to a default threshold. However, the software action uses conditional logic that references the dependencies and the default threshold to adjust the alarm threshold. The alarm threshold can be adjusted in either an increasing manner (e.g. less likely to trigger a fire alarm) or in a decreasing manner (e.g. more likely to trigger a fire alarm) using the dependencies created from the contextual information. 
     In more detail, in the illustrated embodiment, the event context system  122  maintains dependencies that have the effect of changing the alarm threshold for the associated fire sensor based on context information from non-fire detecting devices. For example, for smoke detector  1   20 - 3 , an increase dependency  140 - 1  concerns whether current system time of the alarm signal is between 5 PM and 8 AM. Such dependency would be created based on the assumption that during those periods of time people would be present and activate a pull box station if a fire were actually present. 
     In another example, smoke detector  2   20 - 1  increases its threshold (becomes less sensitive to fire) if the kitchen motion detector  44  is active due to increase dependency  140 - 2 . Here the assumption is that if people are in the kitchen they might be cooking and therefore generating smoke. Thus, the smoke detectors threshold should be increased. On the other hand, smoke detector  2  has a decrease dependency  140 - 4  which makes it more sensitive when the motion detector  44  in the kitchen  52  is inactive (people are not present in the kitchen). 
     Smoke detector  3  has an increase dependency  140 - 3  that decreases its sensitivity making it less likely to generate an alarm if the stove power monitor  62 - 2  registers that the stove is drawing power, i.e., turned on, and drawing greater than 2 Amp. Here, the logic is that if the stove is working, the generated smoke could be from cooking, and therefore the smoke detector  20 - 1  should become less sensitive. 
     In the case of heat detector  1   21 - 2 , its sensitivity decreases  140 - 5  and specifically its temperature alarm threshold increases when the humidity monitor  75  detects an ambient humidity of greater than 80%. In effect, the threshold for an alarm is increased, making the heat detector  1   21 - 1  less sensitive during high humidity levels. On the other hand, if the humidity level is very low than a decrease dependency  140 - 6  is provided. 
     Heat detector  2   21 - 2  includes an increase dependency  140 - 7  that increases its alarm threshold when the video analytics system  128  determines that people are present based on the video data from surveillance camera  103 - 1 . The logic here is that if people are present in the kitchen then the heat generated may be from their bodies or from their cooking and not be indicative of fire. Therefore the threshold for generating a fire alarm should be increased. On the other hand, if the video analytics system  128  determines that no people are present in the kitchen  52  then the threshold for fire is decreased by a decrease dependency  140 - 8 . 
     The pseudocode listing  82  illustrates how potentially multiple increase dependencies and decrease dependencies are combined by the event context system  122  to adjust the alarm thresholds applied by the monitoring system  120  for each of the separate fire sensors. 
     For example, for smoke detector  1 , if any one of potentially three increase dependencies are true, then the alarm threshold for the device is increased by 50%, thus making the device less sensitive and the monitoring system less likely to generate an alarm. At the same time if any one of three or more decrease dependencies are determined to be true then the alarm threshold is decreased by 50%, in the illustrated embodiment. The final alarm threshold is then determined by combining the default alarm threshold with any increaseFactor or decreaseFactor determined by the analysis of the increase and decrease dependencies. In this way, the system uses context information from non-fire detecting devices to change when fire alarms are generated. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Technology Classification (CPC): 6