Did you have any injuries from the freezing gas? I once made the
mistake of touching the side of a propane tank that was cryogenically
cold. It was an ordinary barbeque cylinder, but I was burning the gas
off at a very high rate through the 'ole Cajun Crawfish Cooker. Well,
before you could say doubble-dog dare, my right hand froze to the side
of the tank. The result: 2nd degree "burns", abscence of fingerprints
for 4 months (scars are smooth), and lingering nerve damage. Some days
it pays to be left-handed.

Harry