This incident shows us that just because a pipe contains a chemical that may not be included in a PSM/RMP program, it does not mean the level of risk is any less. This explosion was caused by construction workers using a cutting torch to remove old piping from a boiler room and cut into a pocket of residual propane. The workers were removing discontinued piping that was used for fueling the boiler. One of the pipes had residual propane still inside it and when workers began to cut the pipe with a cutting torch, the propane flashed inside the boiler room.