I have a fire extinguisher in
every car I drive!
They're pretty much a requirement for any older car as far as I'm concerned. Old wiring, fuel and oil leaks, and more maintenance (ie, increased odds of me messing something up
) all mean a greater risk of fire. And then there's the value/rarity of the car, its not like you can just go out and pick out another E-body at the local dealer even if your insurance company covers the entire loss.
As far as powder vs CO2 - in order to reliably extinguish an automotive related fire with a CO2 extinguisher it would have to be HUGE (or your fire pretty darn small). CO2 extinguishers are great for sensitive equipment (computers etc), but they work by displacing oxygen. Once the extinguisher runs out, the oxygen returns, and everything that was on fire is usually still hot. The CO2 does usually form ice, and cools the air very well, but it vaporizes as soon as it gets anywhere near the fire, so it won't cool the burning objects. Especially true when you're dealing with hot metals. Most CO2 extinguishers are not even rated for class A combustibles (includes plastics). This is why they tell you to empty a CO2 extinguisher even after the flames go out, as the chances of re-ignition are higher than with any other extinguisher type. On fuel fires especially, even if you get the fire out, in short order you will have the
exact same situation, spilled fuel, a hot car, and plenty of fuel vapor, and now no extinguisher. They also have a limited range, as the gas will only go so far from the nozzle in high enough of a concentration to put out the fire. BTW, halon was banned awhile back, so unless you already have one, you won't be able to get one of those.
Dry chemical powder extinguishers are messy, don't get me wrong. But they isolate the fire from oxygen by creating a barrier that stays there long after the extinguisher has run out, so if you get the fire out, it usually stays out. Especially true for small fuel fires, the powder will isolate the fuel AND the fuel vapor, greatly reducing your chances of re-ignition. The most common type, the ABC rated extinguisher, usually contains monoammonium phosphate. This stuff is somewhat corrosive, and can damage electronic equipment. It's definitely not good for computers, but, in a non-circuit board environment (like most of our cars) I wouldn't worry too much about it. Yes, I'd still clean it up thoroughly, but I wouldn't stress about my car never being the same again. I definitely wouldn't be concerned if I fired it off in my engine compartment, which I've done before (not on the Chally fortunately). Under the dash is a little different, and it would be a pain to clean up, but most of the car fires I see (firefighter by trade) start in the engine compartment. And I'd rather have a dry chemical extinguisher for an engine compartment fire, hands down.
Bottom line, I'd rather have to spend some time cleaning up the dry chem powder than have to spend my time filing a claim with my insurance company.