Hmm, it would probably work in an emergency, but there are better options. My concerns with using CO2, versus something like an argon welding tank or compressed air, would be...
1.) In the tank, compressed CO2 is a liquid, and has to be boiled off. Depending on outside temperature and tank design, there is a limit to how fast it can produce gaseous CO2 (though this limit is admittedly high).
2.) In very cold weather, the cooling of the CO2 as it boils off will drop the temperature to a point that it will no longer turn to gas. I use to run into this while playing paintball in winter, as a kid.
3.) If there is any moisture in your air system, the cold CO2 is going to freeze it, in contrast to the air compressor air that is being heated by compression some already.
4.) If you don't have a regulator on your CO2 tank, it's coming out at several hundred PSI. If the regulator freezes or fails, you're going to blow out everything with the overpressure.
5.) As CO2 is released rapidly, it gets cold enough to form dry-ice particles. These too will freeze and clog the air system components.
A lot of that is unlikely, but it's possible. I would prefer to use an argon welding tank or SCUBA tank, because these things just aren't even possible. If I was stuck on the side of the trail somewhere and just needed to get back to civilization though, sure, even CO2 is feasible.
