Page 366 - IGC BOOK

Fire Detection

The earlier a fire can be detected, the more time there is for occupants to escape and the better are
the chances of extinguishing or at least containing the fire. A wide range of devices exists for
detecting either heat or smoke. Each of these has some advantages and disadvantages
Flame Detection

Photoelectric cells detect the emission of infra‑red / ultra‑violet radiation.

Flammable Gas Detection

Flammable gas detectors measure the amount of flammable gas in the atmosphere and compare
the value with a reference value. When this is exceeded the gas supply valve is closed an alarm is
actuated.

Heat Detection

Heat detection can be used as a means of actuating a mechanical control or sprinkler system. The
disadvantage of heat detection is that toxic smoke can be evolved from burning materials long
before sufficient heat is generated to trigger the mechanism. These systems are rarely relied upon
as a means of raising the alarm, however where fires raise little smoke, e.g. solvent fires, fixed
temperature or rate of rise detectors can be used.

Fusible Links

Sensors operated by the melting of a metal (fusion detectors), e.g. used to open automatic smoke
vents and close ventilation system dampers and shutters; or expansion of a solid, liquid or gas
(thermal expansion detectors), e.g. to actuate sprinkler systems.

Thermal Expansion, Fusible Solder Link Sprinkler Head Thermal Expansion, Quartzoid Bulb Sprinkler Head

ENSIGN | Unit IG2 – Element 10 –Fire 21