Smoke detectors provide the earliest means of fire detection and should always be considered before heat detectors for fire detection.
There are environmental conditions such as dust and humidity that present complications for smoke detectors. However, heat detectors tend to be immune to these conditions and can then be used as an alternative.
Flames from a fire must reach one third of room height before heat detectors trigger and are therefore considered a slow means of fire detection.
Heat detectors must never be installed in fire escape corridors or computer rooms. They should also be avoided in "clean" electrical equipment rooms.
They should not be used in gas discharge circuits unless environmental conditions dictate otherwise.
There are also certain types of fires that do not emit smoke e.g. alcohol fires so heat detectors are preferable. Where there may be complications with the environment one should consider the use of the multi criteria detectors that look at fire signatures of comparable levels of heat and smoke before operating.
These should be considered before heat detectors.
Heat detectors are NOT recognised as life safety devices and are therefore unsuitable to detect fires in sleeping areas.
In sleeping quarters, like a hotel room, smoke detectors are preferred.
