This is a quote from Goliath_THE_X which was sent to a different mailing list I'm on. For the record he is a chemist and I truxt his word on the matter pertaining to a CO2 tank becomeing a missile. But everyone is free to beleive and thinnk what they like.

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CO2 is the safest thing to use for on-board "air". Compressed air or
any other gas would have to be pressurized to several thousand psi to
store enough gas (potential gas rocket). Since CO2 is stored as a
liquid, it makes it a very attractable source of "air". The worst
thing to worry about would be a tank flipping over in the X and the
valve getting knocked off. So much CO2 would be liberated into the
gas form, that all available oxygen would be displaced. Thus you
wouldn't be able to breath and you would die if you didn't get out of
the truck fast enough. CO2 is colorless and odorless, so if you
don't hear the gas escape it could be too late. But on the bright
side, a CO2 tank wouldn't become a rocket like a tank of compressed
air/gas.

If you don't believe the chemist........ perhaps you will believe
powertank....

"Isn't a CO2 tank like a bomb on my rig?"
NO. Unlike nitrogen or scuba tanks that hold 100% compressed vapor
energy, liquid CO2 goes through an evaporation process before it
becomes pressurized vapor energy and thus CO2 is released in a slower
manner maintaining a much lower tank pressure. This means if the
valve were to get knocked off of a nitrogen or scuba tank it would
become a gas rocket. . If the Power Tank valve were knocked off you
would be able to hold the tank in your hands like a CO2 fire
extinguisher.

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Now I agree that the o-rings will be susceptable to cracking due to cold temps of the CO2, but a properly designed CO2 and ARB setup would allow the Air temp to rise to near normal temps before it ever reached the Locker.

Cliff