Brake cleaner safety statement: The welding hazard question: True or False that residues can generate phosgene gas when welded?

• A. True
• B. False
• C. Not specified
• D. Only under certain conditions

Answer: (A)

Chlorinated brake cleaners can leave residues that decompose when heated by welding. The heat from the welding arc can break down solvents like methylene chloride and other chlorinated compounds, forming phosgene gas (COCl2), a highly toxic substance. Even small amounts can pose a serious hazard in a poorly ventilated area, so this risk is real during welding with any brake cleaner residue present. That’s why the statement is true. To prevent it, avoid using chlorinated cleaners on surfaces to be welded, or ensure complete removal and good ventilation before welding.