RE: Most Dangerous Tool

> Could the flame have backed up into the propane
> canister as I unscrewed it?

Nope, there's no air inside the canister, so the propane can't burn in there.

Part of the reason propane is relatively safe, it has a fairly narrow range of
flammable mixtures.  In effect, it only burns at the interface between propane &
air, where the mixture is just right.  (Unless of course you've gone to great
lengths to mix it just right, like with a carburetor.)

Randall