[M.D. Holloway]

The most common type of freeze can is one containing HCFC and are class II ozone depleters. Not as bad as Freon but still bad for the ozone.

The Montreal Protocal of which he US is a supporter limits the use of CFCs only to the cleaning of absolutely essential industries such as cleaning computer chips. Even thos restrictions are scheduled for rapid phase out.

Use of a HCFC to freeze a bolt would be against the rules established by the EPA to help the US comply with he Montreal Protcol. Use of CO2 gas for the same person would not be illegal but EPA tells me that if you filled a normal aerosl can with CO2 the pressure would be so high it would burst. To sell a can full of CO2 you would have to have much thicker can.

A downside to using freezing to loosen bolts is that freezing make metal brittle so they might snap when you tried to apply force.

So long thread short - I guess it doesn't matter, the idea just doesn't make sense for a product notion...