Upon
ultraviolet (UV) radiation in the presence of
oxygen,
chloroform slowly converts into phosgene by a
radical reaction. To suppress this
photodegradation, chloroform is often stored in brown-tinted glass containers. Chlorinated compounds used to remove oil from metals, such as automotive brake cleaners, are converted to phosgene by the UV rays of
arc welding processes.
[8]
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. If any refrigerant gas was leaking from a pipe or joint, the gas would be sucked into the flame via the sniffer tube and would cause a colour change of the gas flame to a bright greenish blue. In the process, phosgene gas would be created due to the thermal reaction. No valid statistics are available, but anecdotal reports suggest that numerous refrigeration technicians suffered the effects of phosgene poisoning due to their ignorance of the toxicity of phosgene, produced during such leak testing.[
citation needed] Electronic sensing of refrigerant gases phased out the use of flame testing for leaks in the 1980s. Similarly, phosgene poisoning is a consideration for people fighting fires that are occurring in the vicinity of freon refrigeration equipment, smoking in the vicinity of a
freon leak, or fighting fires using
halon or halotron.