We have discussed “pressure testing” and the hazards associated with these required tests many times. This is an example of what can go wrong when doing these tests with a compressed gas vs. hydrostatically! A mechanical contractor was increasing the pressure into the 4-inch compressed air line from approximately 125psi to the TEST PRESSURE of 175 psi a failure occurred. One employee died and the other was seriously injured by sections of piping. (See video of another pneumatic pressure test gone bad)