First things first - please be careful! You would want to get rid of any potential to have the gas soaked garment combust by laying it out, away from any ignition sources, and allowing the gas to evaporate. Then I would recommend that you soak the garment in a bucket with a good dose of detergent overnight. At this point, the garment likely has very little residual gas, and the smell could be cleaned up with a regular wash cycle. If the first one doesn't get all of the odor out, a second cycle may be required.