Methods for detection of flame rely on optical recognition of fire signatures, this is the phenomena introduced to the surroundings by a fire. NFPA 72 categorizes as Radiant Energy–Sensing Fire Detectors , fire detectors that sense the radiant energy produced by burning substances.
UV DETECTORS respond to radiation in the spectral range of approximately 180-260 nanometers. They offer quick response and good sensitivity at comparatively short ranges (0 – 50 ft).
UV/IR DETECTORS, UV optical sensor is integrated with an IR sensor sensitive to both UV and IR radiation emitted by a flame.
MULTI SPECTRUM IR, multiple infrared spectral regions to further improve differentiation of flame sources from non-flame background radiation.
VIDEO IMAGE FLAME DETECTORS employ standard charged couple device (CCD) image sensors, commonly used in closed circuit television cameras, and flame detection algorithms to establish the presence of fires. The imaging algorithms process the live video image from the CCD array and analyze the shape and progression of would be fires to discriminate between flame and non-flame sources.
17.8.2.2* The selection of the radiant energy–sensing detectors shall be based on the following:
(1) Matching of the spectral response of the detector to the spectral emissions of the fire or fires to be detected
(2) Minimizing the possibility of spurious nuisance alarms from non-fire sources inherent to the hazard area
As usual, sound engineering criteria must be employed for a suitable selection and final location of flame detectors
17.8.3.2.1* The location and spacing of detectors shall be the result of an engineering evaluation that includes the following:
(1) Size of the fire that is to be detected
(2) Fuel involved
(3) Sensitivity of the detector
(4) Field of view of the detector
(5) Distance between the fire and the detector
(6) Radiant energy absorption of the atmosphere
(7) Presence of extraneous sources of radiant emissions
(8) Purpose of the detection system
(9) Response time required
References:
-NFPA 72 National Fire Alarm and Signaling Code
-General Monitors Staff, Flame detection Technologies