Every household needs a rubber O-ring. Just recently I borrowed a friend's cooker and discovered it didn't have an O-ring where it connects to the gas tank. Since everyone has some type of propane accessory, like a grill, cooker, heater or torch, more than likely the rubber O-ring is missing or cracked from age.
I don't think this is a real danger because the manufacturer of the accessory would have a warning label with it when it was bought new about such an O-ring. But it would have to leak if it were cracked, costing you money in lost propane.
Check your hoses for cracks. They crack with age. When installing this rubber O-ring, show kids – that way you can explain to them this is the same thing that caused the Space Shuttle Challenger to blow up in 1986.
Chris Miller, Strasburg