That's a good point about the water vapour in exhaust. I was mainly considering it for dirty get-back-moving welding when you're in the middle of the woods using the vehicle alternator/battery as a welder. It doesn't make any sense to have a spool gun with you in the woods if you're going to try that anyway. Just bring rods and arc weld.

I saw some guys who had made bumpers for their Jeeps out of capped pipe, then put fittings on it and filled it with compressed air. So their bumpers did double duty as a compressed air tank. I thought that plus an alternator welder would be a great in the middle of nowhere fix anything solution.