An unusual, tragic cross connection with gas occurred at a propane plant in New England in August 1982. Two houses caught fire, a woman was thrown against a wall when her washing machine exploded, and about 500 people had to evacuate their homes. This incident could have been prevented with the installation of an approved double‐check‐valve assembly on the service line. The article describes common cross connections, causes of cross connections, and keeping the air out by installation of backflow preventers.