Marty, if you're gonna blast someone in the face cause their face is on fire, you're gonna want halotron or halon. Both CO2 and Halon and Halotron displace oxygen to put the fire out.

CO2 is in such a heavy extinguisher cause it is under so much pressure to keep it in liquid form, the tank is steel and heavy duty.

Halon and halotron can be kept in aluminum, much less pressure to keep it in a liquid.

All of them when you release the pressure and shoot it, turn the liquid to a gas. Becuase less pressure difference there is less cold on the halon and halotron.

The C02, you can litterlly point it at the ground and create dry ice with a full shoot off. It is really really cold.

For our purposes, none of them are any better or worse than the other. Halon and halotron are less cold so it changes the cooling of the engine a little bit, but in the short bursts you will use the CO2, man, it just aint a big deal.

Now one thing for everyone to keep in mind, almost every startup fire I have ever seen blown out with a fire ext, they could have easily been blown out with a battery operated leaf blower. Not that it hurts anything to blow them out with co2 or halon, but it is expensive that way.

I only pull the extinguisher out now if I think the airplane is gonna catch. Otherwise I just blow them out.

When I start engines in my garage, I pull down my compressed air line and blow the engnines with compressed air.

FWIW.

Sean