Motor Vehicles and Marine
The Motor Vehicles and Marine domain applies origin-and-cause method to vehicles, vessels, and their distinctive energy systems. Expect questions on compartment-specific origins, fuel and electrical systems, and the hazards of modern high-voltage batteries.
Vehicle fires
Think in systems: fuel delivery, electrical, mechanical and exhaust, and emission controls. Engine-compartment fires commonly trace to fuel line leaks, damaged or aftermarket wiring, or overheated components; catalytic converters can ignite vegetation or leaked fluid but rarely start the vehicle fire alone. Post-crash fires require analysis of deformation, fuel system compromise, and available ignition sources. Determine whether the vehicle was running, recently operated, or modified.
Modern vehicles add high-voltage battery packs. Thermal runaway can begin without an external ignition source, can reignite hours or days later, and creates stranded-energy hazards. Quarantine the vehicle, monitor it, and use appropriate PPE and isolation procedures.
Marine fires
Boats combine gasoline, fiberglass, and confined spaces. Gasoline vapor is heavier than air and accumulates in the bilge; vapor plus a spark produces an explosion with outward deformation of the hull and deck. Shore power systems, galvanic corrosion, DC wiring, LPG systems, and battery charging are recurring sources. The hull identification number identifies the vessel, and salvage plus water damage complicate evidence preservation.
Worked example
A gasoline inboard boat is found with the engine hatch displaced upward and fire damage concentrated above the bilge. Reasoning: outward displacement supports a vapor explosion in the bilge rather than a fire that began above deck. The investigator checks the fuel system for leaks, the bilge blower operation, and the ignition protection of electrical components. Fuel found in the bilge supports the hypothesis, but the ignition source must still be identified or the cause reported as undetermined.
Traps that cost marks
Blaming the catalytic converter by default; overlooking aftermarket wiring and accessories; failing to establish whether the vehicle was operating; treating an electric-vehicle battery fire as extinguished when it can reignite; ignoring salvage and water damage when reading a vessel's fire patterns.