Buses, heavy-duty trucks, waste trucks, electric and hybrid vehicles and construction, mining and farm machines all run heat sources close to fuel, oil, debris or high-voltage batteries. An onboard system protects those compartments automatically: a heat-sensing tube bursts at about 375°F (190°C) and releases water mist without electrical power, giving people time to get out and limiting the damage.

A transit bus can pull away from a stop with its rear engine compartment already burning, while the driver sits at the far end with no view of it. Haul trucks, garbage trucks and combines carry the same risk: hot engines and hydraulics running inches from fuel, oil and packed debris.

Because these fires start where no one can see them, a fire suppression system installation is planned around the hot spots of each bus, truck or machine. This guide covers which vehicles carry the highest risk, what starts the fires, what one fire costs a fleet, and how an automatic system responds.

Any vehicle with an engine, hydraulics or a large battery can burn. Five groups combine a high fire risk with a high cost when it happens.

Most transit buses and coaches carry the engine at the rear, where the driver cannot see or smell a fire until it is well-established. Dozens of passengers then have to leave through a few doors. A school bus adds children who may need help getting out.

Europe now requires automatic engine-compartment suppression on new bus and coach types with the engine behind the driver, phased in under UN ECE Regulation 107 between 2018 and 2020.

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