What snrub said, if you have an old gas motor like a briggs or similar, hook the exhaust up so that it blows into an opening and let it run for a 15 minutes, even choke it as much as will allow it to run. will remove all the oxygen out of the tank and you can cut on it as you please, safer then water that will just concentrate the gas fumes into a smaller area, not deactivate them, and also pretty much impossible to cut underwater.
