vented box for Honda 2200 generator

Texaco dealer in Athens, Ga in the early 70's. Truck was unloading one summer night into a bulk tank at the distributorship. Humidity was high and air was still. In one of the buildings at the distributorship was a waterheater with a gas pilot light. As the hollow where the plant was located filled with fumes, they reached the pilot light and the whole area blew up. We heard the explosion from 15 miles to the north. Windows were blown our of many of the businesses in downtown from the concussion. The public housing across the street and up on the hill had a building that had to be torn down because it lifted second floor off the walls. The driver was badly burned but not killed. Every fire dept in the area sent trucks to help contain the fire. It burned all night and into the next day.
Fumes will explode. I was there helping evacuate the folks in the housing apts.