OK, as Deputy Chief of a Fire Department on the top of a really big hill on a medium-sized highway, we deal with vehicle fires more than any other type of call. In the summer we may get two vehicle fires in a week. Please let me know if any of the below info doesn't make sense.
If you have a small electrical fire in the dash, you usually notice the smoke when the fire is tiny, and you can usually knock it out with anything. So a small (2 pound) BC extinguisher in each door of your truck would be a fairly safe bet for in-cab fires. Anything bigger and people end up mounting it behind the seat, or behind the fridge, and can't get it fast enough when they really need it. You want the extinguisher in your hand and ready to go within about 3 seconds of shutting off the ignition and taking off your seat belt. And you want to know how to use it, so buy an extra one and use it on a practice fire (and get your spouse/partner to practice as well) so that you are not reading the directions when you really need to use it.
For a serious engine fire, bigger is better.
As an example, we have put 1500 gallons of foam into an engine compartment on a Dodge Diesel Pickup and that sucker was still burning. Granted, usually by the time we get there with our truck, the fire has really taken hold.
But I would say carry a 20-pound ABC at a minimum for it to give you a good chance of putting a fuel or oil based fire out if the engine or tranny is hot.
(FYI - We have more fires starting in the tranny than any other part of the vehicle).
Also adding a 20-pound class D would be good if you have space for it and can afford it.
Make sure they are regularly checked, and also check the mounting brackets every month to make sure they stay secure on the trail, but come off properly when you need them. They should cost you between $150 and $200 each for the ABC's and about $400ish for the D.
Don't worry about the corrosion factor. You can deal with it after the fire is out. But if you don't get it out in the first couple of minutes, you are buying a new truck anyway.
Note - I would never recommend the average person using a water-based extinguisher on a vehicle fire. Even though we regularly use water/foam, we have all our protective gear on, and attack the fire at a greater distance than you would be using an extinguisher.
We use a Halligan Bar or Kelly Tool to open the hood to allow us to attack from a safe distance. The way we do this is to hammer a line diagonally across the hood, and then we pry up one corner, giving us a deflection shield, and maintaining containment while still allowing foam access from 40 feet away. Of course, we destroy the hood of the vehicle in the process.
You would likely be kneeling next to the truck trying to spray up and in. You would be closer, and much more exposed.
What is the danger with water? Pretty much EVERY vehicle made today has a lot of magnesium-alloys in the build. And that is all over the vehicle. A classic training video we use shows a fire-fighter spraying water into the drivers' window on a car fire, and there was a magnesium-alloy in the steering-column on this particular make. The blast blew the doors off, and tossed him about 30 feet away into the ditch. Even with non-magnesium-alloy parts, the cold water hitting hot steel often makes things blow apart. I have been peppered with bits of steel from 40 feet away. That's why we wear the big funny-looking helmets. :ylsmoke:
I would be very cautious about attacking a modern-vehicle fire with a water-based extinguisher if I was dressed in street clothes. If that's all you have, and someone is in the car, you do what your conscious tells you that you need to do to get them out. But if the vehicle is un-occupied, just keep the other traffic away, and call the insurance company.
Regarding class D fires, you may carry one for 20 years and never need to use it. But if you know you have a magnesium-alloy steering column, and you have a fire in the cab, or if you have a wheel fire with magnesium/aluminum-alloy wheels, then having that Class D extinguisher on the outside of your truck will quickly go from a $400, 20-pound piece of bling, to the savior of your $50,000 truck. Even more common alloys can be an issue. Most people think aluminum is pretty safe, but burning aluminum can cause unpredictable outcomes. When mixed with water it can produce hydrogen, which will make your simple wheel fire pretty exciting.
Cheers
Ray
