What's this CO2 stuff about. I use CO2 for my onboard air, but for fire exting too? Obviously there must be something different.
mmmmmm, a methane BBQ, sounds good.....
It is one and the same stuff. Fires rely on the 'fire triangle' of heat, oxygen and fuel to burn. Fire extinguishers focus on knocking one or more of these elements out of the chain to contain the fire. For example, water is used to cool fires, dozers are used to remove fuel in forest fires, and the one I always love, the use of explosives to put out oil well fires - consume the oxygen, quickly!
My understanding is that dry chem units operate by smothering the fuel source and starving the fire of oxygen. In fact, a by-product of the chemical decomposing is CO2 (from what I remember) which also helps to displace oxygen.
Pressurized, liquid CO2 works on the same basis. As it is released, it creates a gas (like it does when it fills your tires). The CO2 displaces the oxygen and helps to contain the fire by smothering it in CO2. There may be a bit of a cooling element, but probably not that important for a raging fire.
While both dry chem and CO2 are quick to go (usually 10 seconds), you would be amazed how how effective they can be. In a previous life, I used to get annual training at a fire station. They would give us a small dry chem fire extinguisher and light a 'flash pan' filled with diesel fuel (something like 10' x 8'). You would approach the fire and S L O W L Y loft the chemical onto the fire, smothering it from front to back. You can conain a fire of this size if you are careful. If you 'shoot your load too fast' :ugh: you will find that the fire doesn't go out and you spread flaming fuel everywhere!

If you can't contain the fire and your extinguisher is gone, drop it and back away facing the fire and wait for the pros!
Not sure what you would have to do to mod a tire unit to fight fires.
Cheers, Hugh