Yes. Look at http://brucegoldfarb.com/?p=28 to read of a restaurant that was just about as obliterated from a single 20-pound cylinder.

Propane tends to accumulate in the basement. It's heavier than air, and it can lose its smell. Your house could be filled with an explosive mixture, and you could be totally unaware.

Propane detectors are absolutely essential. Unlike a smoke detector, which is installed on the ceiling, a propane goes on the floor or the lowest point.