Fire detectors with environmental data input

[0001] The invention pertains to regional monitoring and alarm systems. More particularly, the invention pertains to such systems which automatically respond to environmental characteristics throughout the region to adjust an alarm detection process.

[0002] Various methods are known for combining signals from different types of sensors in order to distinguish fires from nuisance conditions. These multicriteria detectors are intended to sense the earliest fire products in order to achieve a quick and accurate response. Representative forms of processing are disclosed in each of Lee D. Tice, Fire Detection System and Method Using Multiple Sensors, US 2006/0119477 A1, Jun. 8, 2006; Lee D. Tice, Multi-Sensor Device and Methods for Fire Detection, US 2006/0181407 A1, Aug. 17, 2006; Lee D. Tice, Multi-Sensor Device and Methods for Fire Detection, US 2004/0189461 A1, Sep. 30, 2004; Lee D. Tice, Multiple Sensor Apparatus and Method, U.S. Pat. No. 5,483,222, Jan. 9, 1996; Lee D. Tice, Apparatus Including a Fire Sensor and a Non-Fire Sensor, U.S. Pat. No. 5,659,292, Aug. 19, 1997; Lee D. Tice, Multi-Sensor Device and Methods for Fire Detection, U.S. Pat. No. 7,068,177 B2, Jun. 27, 2006, assigned to the assignee hereof and incorporated by reference.

[0003] Currently, in known systems, end-users can only select a detector sensitivity (or in rare cases specify descriptive labels, such as “lobby”). End-users are often not well equipped to properly select a sensitivity for a given space.

[0004] In addition, performance based codes are becoming more prevalent. Performance based codes provide placement of detectors based on system performance goals (such as building occupants evacuated in 60 seconds) rather than prescriptive requirements (such as one detector every 30 feet). As the change is made to performance based codes, fire detection systems that support detectors that are aware of their environment will become more valuable.

[0005] It has also been recognized that when smoke detectors are positioned in a high airflow area (such as near a vent), their response can be delayed or entirely disabled. Furthermore, other ambient conditions can make false alarms more likely (c.f. shower steam).

[0006] There is thus an on-going need to be able to incorporate environmental information into alarm decision processing so as to enhance performance and to improve reliability. It would be preferable if such information could be acquired and updated, automatically, to the greatest extent possible while the system is carrying out normal processing.

[0011] While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, as well as the best mode of practicing same, and is not intended to limit the invention to the specific embodiment illustrated.

[0012] Embodiments of the invention function to optimize alarm decision processing methods before a fire breaks out. Data can be entered manually that describes the space (context) in which the detectors reside. Data can also be gathered by the detectors themselves and acted upon directly or in processed form. The alarm decision methods could be adjusted based on patterns of prior conditions or a fixed set of prior conditions

[0013] Data could be processed at the detector(s) or at the system control panel. Detection processing commonly takes place in both the detector(s) and the system control unit, or, panel. Embodiments of this invention thus include methods for increasing the speed and accuracy in the detection of fire using fire detectors in combination with additional environmental information.

[0014] In one aspect of the invention, fire detection is implemented using two new methods. First, the fire alarm system—either the detector or the control panel—will provide for the input of initial conditions about the space that is being protected. Typically, detectors are set to one of several sensitivities throughout a building based on an educated guess on the part of the system designer. In accordance with the invention, a system designer will input the dimensions of the room or space and other parameters important to the development of a fire. These parameters will be factored into the alarm decision processing along with the amount of smoke that is sensed. Second, the fire detectors can use inputs from a multisensor arrangement to optimize the sensing of fire. Typically, multicriteria detectors use different sensors to sense the various fire products. In accordance with the invention, the multiple detectors can be used to adjust the detection processing before occurrence of a fire.

[0015] In some known fire alarm control units, or panels, there are user interfaces that show maps of the protected premises. This same information can be used as an input to the alarm decision processing. For example, a higher ceiling may warrant higher sensitivity. Higher airflow (as in a hallway) may warrant greater smoothing. This represents additional information, provided by the user or installer, on which to base an alarm decision.

[0016] The detector(s) can also provide important information before the fire. If the detector(s) sense abnormally high temperatures at the ceiling, there may be greater stratification and sensitivity may need to be increased. Perhaps the detector will sense increased CO₂. That may mean that the likelihood of fire is lessened. An increase in O₂ may mean greater propensity for fire—or a hotter fire. Detection can be optimized based on information gathered before the fire—possibly even hours, days, or weeks in advance. This information can be provided manually by the user or automatically acquired by the detectors themselves.

[0017] Exemplary Manually Input Information

• • [0018] Use building floor plan as manual input data (ceiling height, room length, width)
    • [0019] Info is already input into some fire alarm control panels to aid responding firefighters
  • [0020] Expected temperature
  • [0021] Typical air changes
  • [0022] Is the space on an outside wall?
  • [0023] Is there natural light in the space?
  • [0024] Fuel load—furnishings, chemicals, etc.
  • [0025] Type of occupancy?
  • [0026] Expected use of space?
  • [0027] Type of HVAC?
    • [0028] Heat: electric (resistive), natural gas, hot water

[0029] Exemplary Automatically Sensed Information

[0030] Sensors could be co-located or remote from one another

• • [0031] Airflow
    • [0032] Could use the dual thermistors on detector
    • [0033] Could adjust detector sensitivity based on airflow
      • [0034] Higher sensitivity with high airflow
      • [0035] More drift compensation with high airflow
      • [0036] More smoothing with high airflow
    • [0037] Could generate a trouble condition with excessive airflow
  • [0038] Absolute temperature in room at ceiling
    • [0039] Possible pre-stratification information
    • [0040] Is high temperature (120 F) indicative of no occupants?
    • [0041] Is temperature trend information a proxy for occupancy
  • [0042] Temperature delta between two heights in room
    • [0043] Pre-stratification information
    • [0044] Could be done with two beam detectors at different heights
      • [0045] Could IR be used for temperature detection?
  • [0046] Occupancy
    • [0047] High CO₂ indicator of occupancy?
  • [0048] Cleanliness (number of dust particles)
    • [0049] Could be done with a photo chamber
  • [0050] Increased hazard
    • [0051] Increased level of oxygen?
    • [0052] Flammable gases
  • [0053] Visible light
    • [0054] Day/night adjustment from outside light
    • [0055] Occupancy based on artificial lighting
  • [0056] Humidity
  • [0057] Sound
    • [0058] Indicator of occupancy?
  • [0059] Are building utilities being used?
    • [0060] Phone, electric, gas, water usage to indicate occupancy?

[0061] In another aspect of the invention, ambient sensors (flow, temperature, humidity) can be added to a smoke detector to monitor the ambient environment for out-of-specification conditions. This would allow the smoke detector to signal a trouble condition, or take other actions to prevent non-operation or false alarm.

[0062] Smoke detectors or thermal detectors often include heat sensing thermistors to provide an additional type of fire indicating output. Thermistors can be configured as airflow sensors. With software and circuitry in accordance with the invention, the thermistors can be pulsed at higher power, raising their temperature. The rate of cooling can be correlated with the rate of airflow. The smoke detector can check airflow at either random or periodic intervals to assess whether it is installed in too high an airflow area, and signal the condition either locally, or at the control panel.

[0063] Duct smoke detectors require a minimum airflow to operate. By adding an airflow responsive thermistor to a duct detector, it is possible to detect and to signal a trouble condition when insufficient airflow is present. Insufficient airflow could be caused by a filter loaded with dust, and needing maintenance, providing an obstruction. Such conditions could be sensed with one or more local thermistors to then generate an environmentally based trouble indicating signal.

[0064] Humidity/condensation sensors can be added to a smoke detector to signal a poor placement condition (c.f. near a stove, bathroom, or other steam source) locally or at the control panel.

[0065] FIG. 1 illustrates a system 10 which embodies the present invention. The system 10 incorporates a plurality of detectors 12 which are, via a medium 14 in communication with a fire alarm control unit 18. Detectors 12 can be different and unlike one another. They include one or more ambient condition sensors of smoke, temperature, flame and the like all without limitation. They can also incorporate one or more gas sensors.

[0066] Medium 14 can be implemented as a wired or wireless medium all without limitation. Wirelessly coupled detectors, illustrated by a plurality of detectors 20 could be in, for example, RF communication with the control unit 18.

[0067] Detectors 12, 20, representative examples, which have been illustrated in previously noted published patent applications and issued patents assigned to the assignee and incorporated by reference herein, are illustrated in FIG. 1 installed in and monitoring a region R. The region R could be a single story region or a multiple story region all without limitation.

[0068] The alarm control unit 18 can include one or more programmable processors 18a as well as executable software 18b. Control unit 18 can include a graphical display device 18c and a manually operable input device, for example a keyboard 18d.

[0069] Those of skill will also understand that while conventionally one or more fire alarm control units, such as the control unit 18 would be located adjacent to or within a portion of the region R, those units could be at least in part displaced from the region R and in communication with the detectors 12, 20 via one or more computer networks such as the Internet.

[0070] Those of skill in the art will understand that the detectors of the pluralities 12, 20 could each include one or more programmable processors and associated software for carrying out various aspects of alarm processing. Some or all of the alarm processing could be carried out in control unit 18. Neither the exact location nor the precise form of alarm processing represents limitations of the present invention.

[0071] FIG. 2 is a flow diagram of processing 100 in accordance with the invention. Initially the detectors are installed in the region R, 102. Space related and other parameters can be manually entered into the system 10, 104. Selected ambient conditions can be automatically sensed 106.

[0072] The alarm processing can be adjusted or optimized in accordance with the entered parameters and sensed conditions, 108. The region can then be monitored 110 on an ongoing basis. It will be understood that the automatic sensing can be periodically reinitiated to carry out further adjustments and optimization of the alarm processing 108 in real-time. The region monitoring 110 can then be reinitiated.

[0073] The results of modifying alarm processing could also be displayed on device 18c for use by an operator. Regional characteristics can be manually entered by an operator via keyboard 18d.

[0074] Those of skill in the art will understand that the types of processing disclosed above and in the various published applications and issued patents incorporated herein by reference are representative and illustrative only. Other forms of alarm processing can be utilized in accordance with the invention where such are susceptible to being adjusted and optimized in accordance with the space related parameters as well as the automatically sensed ambient conditions as noted above.

[0075] FIG. 3 illustrates an exemplary smoke detector 30 of a type that might be incorporated into the pluralities 12, 20 discussed previously. Detector 30 incorporates a smoke sensing chamber 32 and one or more thermistors 34. The thermistors 34 are oriented so as to be exposed to ambient airflow 38, from the region adjacent to the respective detector 30 which may or may not contain smoke.

[0076] As those of skill in the art understand, smoke detectors, such as the detector 30, require a range of airflows to operate correctly. If the airflow is too low or too high, the respective detector may not respond correctly. For example, a detector installed near a vent may not respond to smoke as fast as desired since the smoke might be diluted by fresh air coming from the vent. Alternately, a slow response is possible in connection with duct smoke detectors where low airflow can result due to one or more filters of the respective detectors being clogged with dust.

[0077] While the thermistors 34 can be used to sense heat from developing fires, which provides an alternate form of sensing to the smoke sensing chamber 32, those thermistors can also be used to detect airflow at the respective detector.

[0078] FIG. 4 illustrates aspects of circuitry of the detector 30 which can be coupled to the thermistor or thermistors 34. Such circuitry could include detector control circuits 40 which those of skill in the art will understand could be implemented, at least in part, by a programmable processor 40a and associated, executable control software 40b. The control software 40b can be recorded on a computer readable medium which is coupled to the processor 40a.

[0079] Control circuitry 40 is in turn coupled to a source, such as a voltage source 42 and a current control element 44. The current control element 44 can be in turn coupled to thermistor 44 as well as an input, see line 46, to the control circuits 40.

[0080] The source 42 can be used to couple electrical energy to the thermistor or thermistors 34 thereby raising their respective ambient temperature or temperatures. The amount that the respective temperature or temperatures increases is related to ambient airflow 38 by a known relationship. Output voltage, on the line 46, which can be processed in either analog or digital form via control circuits 40 indicates the temperature of the thermistor or thermistors 34. That temperature indicator is also related to airflow across the respective thermistor or thermistors. Where indicated airflow is either too low or too high the control circuitry 40 can indicate a need for maintenance or indicate a trouble condition via the medium 14 to the system control circuitry 18. The control unit 18 can in turn notify an operator that a respective member of the plurality 12 or 20 is indicating either low airflow or high airflow which can then be investigated and evaluated. Necessary maintenance functions can then be carried out relative to the respective detector or detectors.

[0081] It will be understood that the illustrative detector 30 could be implemented as either a duct smoke detector or a ceiling mountable smoke detector without departing from the spirit and scope of the present invention.

[0082] From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.