Human beings them selves is best detector of accidental fire when conscious and present in the vicinity. However, it is not always possible and not even desirable to leave detection of fire at their capacity, availability and efficiency for they can not remain present at all the places, time and environmental conditions.
Unwanted fire / Accidental is very devastating in nature by its own phenomena and / or its related by-products. Immediate after incipient stage, it can be detect on smoldering, flame and heat, or decay stage. Detection in finishing or decay stage has no mean by its principle, because there will not remain to save except adjacent areas to prevent.
Fire can be detect by sensing the presence of one or more of the manifestations of combustion, i.e., heat, smoke, flame, fire gas, radiation. Looking to the fire characteristics, Heat Detectors, Smoke Detectors, Radiation Detectors and Gas Detectors are available. We can use them in such a different manner according to the best fit. Spot type, Line type, Air sample type is the example of it. Hence operational mode can be select Non-restorable , Restorable or Self restorable mode.
An interesting thing is selection of such detectors to assume the probability X Consequence calculation. BS 5839, L.P.C. Rule; IS 2189 codes are best reference for above.Fixed Temperature, R.O.R., Rate Compensation, Linear Heat Sensing, Fluid Expansion types are example of Heat detector; Ionisation, Optical, Beam, Air Sampling can be give reference to a Smoke Detector; Electromagnetic Radiation Fast Response, IR, UV, UV&IR, Spark / Ember, Laser Beam are comes under Flame detection; Semi Conductor Based, Catalytic Element Based, Ultrasonic Based is Gas Sensors.
Fire in enclosure has its own nature to develop and spread depend upon specific structure and arrangements. There are several preventive methods is in practice and remains must be cover in this scope in interest of “Life and Property Safety”. It may meaningless if selection of detector/s, installation according to engineering calculation will not fit to the target area/s. Factors affecting performance of fire detectors mainly in four type: Sensitivity, Reliability, Maintainability, and Stability. Sounding a fire alarm by automatic detection in an enclosure also propagate calculation of Fire Dynamics as well as its positioning.