 Chlorinated solvents used to remove oil from metals, such as automotive brake cleaners, are converted to phosgene by the UV rays of arc welding processes.Phosgene may also be produced during testing for leaks of older-style refrigerant gases.Chloromethanes (R12, R22 and others) were formerly leak-tested "in situ" by employing a small gas torch (propane, butane, or propylene gas) with a sniffer tube and a copper reaction plate in the flame nozzle of the torch.