Some hazards require special consideration with fire protection being provided by more than one type of fire detection media.
One of these schemes is where infra-red fire sensors are installed together with Linear Heat Detector Cable (LHDC). Two types are employed as each has specific beneficial characteristics:-
Infra-red fire detectors excel at sensing fast moving hazards.
LHDC provides extensive coverage in static harsh environments.
Coal Conveyors are a particular application of this combined scheme. The use of volatile fuel such as PRB coal makes the correct protection of coal handling plants essential, as the risk of potential loss is greatly enhanced.

A fire condition within a conveyor system may be considered to be :-

A "static" fire - On a stationary conveyor belt, or within the conveyor mechanism / housing.

A "moving" hazard - Hot or burning coal imported onto a traveling conveyor belt.
It has been established that each of the above requires a different form of fire detection to provide a reliable fast responding and trouble free system.
See: Fire Protection Guidelines for Conveyors Transporting Coal