General Knowledge: Vehicle Fires

14 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.

Sources: 49 CFR 393.95, TC 21-305-20 para 4-14, TC 21-305-20 para 4-15, TC 21-305-20 para 4-16, TC 21-305-20 para 4-17, TC 21-305-20 para 4-18, TC 21-305-20 para 4-19, TC 21-305-20 para 4-9

What you need to know

393.95(f) permits either three bidirectional emergency reflective triangles conforming to FMVSS No.

125, or at least 6 fusees, plus as many additional fusees as 392.22 requires. Other devices may be added but not substituted.

Warning devices for stopped vehicles

one of the following options must be used: (1) Three bidirectional emergency reflective triangles

or (2) At least 6 fusees.

49 CFR 393.95

393.95(j) requires each fusee to be capable of burning for 30 minutes.

None of the figures offered is the one the rule gives.

Each fusee shall be capable of burning for 30 minutes.

49 CFR 393.95

393.95(a)(4) requires the extinguisher to be filled, located so it is readily accessible for use, and securely mounted to prevent sliding, rolling or vertical movement.

A locked compartment would conflict with ready accessibility.

The fire extinguisher(s) must be filled and located so that it is readily accessible for use. The extinguisher(s) must be securely mounted to prevent sliding, rolling, or vertical movement relative to the motor vehicle.

49 CFR 393.95

393.95(a)(5) requires an agent that does not need protection from freezing, and compliance with the EPA SNAP toxicity provisions.

The agent type is not otherwise specified.

The fire extinguisher must use an extinguishing agent that does not need protection from freezing.

49 CFR 393.95

393.95(a)(1)(ii) allows either a single extinguisher rated 5 B:C or more, or two each rated 4 B:C or more.

A single 4 B:C unit is not sufficient on its own.

A power unit that is not used to transport hazardous materials must be equipped with either: (A) A fire extinguisher having an Underwriters' Laboratories rating of 5 B:C or more; or (B) Two fire extinguishers, each of which has an Underwriters' Laboratories rating of 4 B:C or more.

49 CFR 393.95

Get the fire away from anything else that can burn.

A service station is the worst possible choice, which is why the manual names it specifically: you would be parking a fire next to fuel storage.

When it is discovered that a vehicle is on fire, pull it off the road in an open area away from buildings, trees, brush, vehicles, or anything else that might catch fire. Do not pull into a service station.

TC 21-305-20 para 4-15

Opening the hood feeds the fire a rush of air and can turn a contained engine fire into a blaze in your face.

Shutting the engine off stops fuel being pumped to it. Shut the engine off as soon as you can: opening the hood feeds air to the fire.

With an engine fire, turn off the engine as soon as possible. Do not open the hood if avoidable.

TC 21-305-20 para 4-15

Aiming into the flames wastes the charge; the fuel is at the base.

Standing upwind lets the wind carry the agent onto the fire instead of carrying flame onto you. Aiming at the flames rather than the base wastes the extinguisher entirely.

Stay far away as possible from the fire. Aim at the source or the base of the fire, not up in the flames. Take a position upwind from the fire.

TC 21-305-20 para 4-17

The letters are fire classes, not sizes.

This is why 393.95 specifies a B:C rating for a CMV: the fires you expect are fuel and electrical. An A rating adds ordinary combustibles like cargo. A, B and C adds wood, paper and cloth.

B and C rating extinguishers are designed to work on electrical and liquid fires. The A, B, and C type extinguishers are designed to work on burning wood, paper, and cloth; as well as electrical and liquid fires.

TC 21-305-20 para 4-16

Opening the doors gives a smouldering cargo fire the oxygen it has been starved of.

The manual says cargo fires are usually found by smell or by smoke escaping around the doors, and that the doors stay shut until you are somewhere safe with help. And not until help is available.

unless an adequate source of firefighting equipment is available, do not open the cargo doors or remove the tarpaulin until the vehicle has been moved to a safe location where help (preferably from a fire department) can be obtained

TC 21-305-20 para 4-18

Both routes are heat from friction.

An under-inflated tire flexes more and heats up, and a locked wheel grinds one patch against the road. Dual wheels are called out because heat builds between the pair. A tire dragged by a locked wheel can begin to burn for the same reason.

Tires that are not inflated properly generate excessive heat during operation. This may result in the tires igniting, especially in dual-wheeled vehicles. Tires dragged along the road surface because of a locked wheel may begin to burn.

TC 21-305-20 para 4-19

Engine off and a 50-foot exclusion on smoking and flames.

Note 397.13 sets 25 feet for smoking near a placarded hazmat vehicle, so the two figures govern different situations and are not in conflict. Both conditions apply throughout refuelling. None of the figures offered is the one the rule gives.

Turn off the engine during refueling. Do not allow smoking or open flames within 50 feet of a vehicle during fueling or at an accident scene where there is danger from spilled gasoline or other flammables.

TC 21-305-20 para 4-9

Knowing when not to fight a fire is part of the procedure.

The manual is blunt that attempting it with inadequate equipment endangers lives, and says to send for professional firefighters when possible. Inadequate equipment endangers you and others, and still fails to put the fire out.

if the fire is out of control, attempting to extinguish it with inadequate equipment not only diminishes the possibility of successfully extinguishing the fire, but it also endangers the lives of the operator and others nearby

TC 21-305-20 para 4-14

Contact bonds the nozzle to the tank so no static charge can build between them and jump as a spark.

The same reasoning is why a tactical refuelling vehicle is bonded to the vehicle it is filling.

Keep the gasoline nozzle in contact with the gas tank when fueling.

TC 21-305-20 para 4-9

Check yourself

• What must you carry to satisfy the warning device requirement?

• What is the minimum burn time for each fusee you carry?

• How must you carry a required fire extinguisher?

• What is required of the extinguishing agent in the fire extinguisher you carry?

• What two extinguisher arrangements satisfy the rule?

• How do you choose where to stop when your vehicle catches fire?

• How should you deal with the hood during an engine fire?

• How do you use a fire extinguisher correctly?

• What are the fire types a B:C extinguisher covers?

• Should you open the trailer doors when you suspect a cargo fire?

• How can your tire start a fire?

• What two precautions does the manual give for refuelling?

• What should you do when a fire exceeds what your extinguisher can handle?

• Why keep the nozzle touching the filler neck while fueling?

Answers are in the practice test for this topic.