LPG odorant concentrates in refinery processing lube oil. One day in Lee Vining, CA. I emptied the oil out of a pot that saw a lot of use in Mexico. Those were the days when the dump would magically catch fire once a week. The oil was dumped on cardboard. Not a drop hit the earth.
Move kleige lights and boom mikes...
Fire department responds to emergency. "Massive LPG leak at disposal site"
Methyl Ethyl Mercaptans hold the Guinness Book record for the smelliest stuff on earth.
So...when leak testing is inconclusive check for oil stains near the filler and 10% valve. Clean with smelly carburetor cleaner followed by alcohol.