Evan, I use either Nitrogen or CO2 gas as a purge when I'm welding or cutting on fuel tanks. Set up a pressure regulator at a slow constant flow into the tank and lei it run for a couple of minutes to displace all the oxygen.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!