I have a couple of small fire extinguishers that I need to get recharged and get at least one put in the truck. VERY important thing to have IMHO...although one thing people forget is that they need to be inspected periodically, and looking at the gauge doesn't necessarily cover it! I had a full fire extinguisher in my old van, and I guess the pressure relief valve went bad or something on those lines. It started hissing, and I barely had time to get it out of the cab before it started discharging on its own
I think there were still chemicals in it (don't remember which type of extinguisher it was), but it discharged until it was completely depressurized.
FWIW this discussion reminds me of some training I did with the Scouts at a Coast Guard station a number of years back. They had pots filled maybe 1/4 of the way with diesel fuel, and they would ignite the fuel and, after a safety/how-to lecture, send a kid (dressed in full fire gear) with an extinguisher to put the fire out. It was meant to train the kids on how to properly operate a fire extinguisher to put out a shipboard fire. The USCG people had to use a lit flare to ignite the fuel in the pot, and even with the flare, it took a full minute (or even longer if the wind picked up) to get the fuel burning...
I would recommend a dry-chem ABC extinguisher...they're messy, but you'll be able to put out any fire that you'll see on one of these trucks (or on any vehicle, unless you have a car with magnesium wheels....if a mag wheel catches fire {a rare Class D fire}, you may as well break out the Smores
)...