The engine compartment in a truck is narrow and hot, with many potential hotbeds.
A hot engine shares a limited space with hydraulics and fuel tubes, electric installations, compressors, heaters and much more that can constitute fire hazards.
The course of event of a fire in an engine compartment is often fast and difficult to suppress with only a hand extinguisher.


Read more here:

Fire suppression for all engine compartments (pdf folder)