A number of years ago we were camped in Wells Grey park in central British Columbia. An elderly neighboring man in a truck camper put on a percolator coffee pot in the morning to make coffee and went out to prepare his boat to go fishing for the day. He forgot about the coffee pot and went off fishing.
Several hours later he returned. Being a heavy smoker, he lit a cigarette and headed for his campsite. Fortunately he stopped to talk with some other campers. He finished his cigarette and looked for another before heading back to his camper. He was out of cigarettes so he returned to his camper.
When he opened the door, he was almost overcome by the propane fumes that had filled the camper. The coffee pot had boiled over in the morning and put out the flame on the burner, leaving the propane to escape filling the camper with the gas. He said that he was very lucky, as he almost always had a cigarette going and would very likely have had one going then if he hadn't run out.
Luckily as well, none of the other possible ignition sources in the camper ignited the propane, as that would have been a huge explosion.