For those who dont believe that open flame heaters can be dangerous, here is my story:
I sold a 70 Z/28 to a friend. I delivered it to his house and we put it in his 2 car garage. That night, the garage exploded so the fire investigator naturally looked at the car for a gasoline leak. Come to find out, his lawn mower gas tank leaked. His water heater had a pilot lite flame and the heater was about 2 ft above the garage floor. When the gasoline fumes reached the 2 ft deep level, the pilot light lit the mixture. It blew the garage door across the alley to hit the house behind him. The explosion moved the exterior garage wall outward about 6" and the garage floor was cracked. I did not harm the car at all. Think about it... a 16' x 8' garage door is about 18,000 sq inches and a gasoline explosion that produces only 0.1 psi means the garage door was hit with almost an instantaneous force of a ton.