During welding, exposure to vapors from chlorinated hydrocarbons can produce which gas?

• A. Ammonia
• B. Phosgene Gas
• C. Sulfur Dioxide
• D. Chlorine Gas

Answer: (B)

Exposure to vapors from chlorinated hydrocarbons during welding can produce phosgene gas. At welding temperatures, chlorinated solvents or cleaners can decompose in the arc or on hot metal, releasing chlorine. In this hot, oxygen-containing environment, chlorine can combine with carbon monoxide (from incomplete combustion) to form phosgene (COCl2). Phosgene is a highly toxic gas that irritates the eyes, nose, throat, and lungs, with the potential for delayed pulmonary edema, so even small exposures are dangerous. To prevent this, avoid chlorinated solvents near the weld, ensure adequate ventilation, and remove any chlorinated contaminants from the work area. Ammonia, sulfur dioxide, and chlorine gas are not the typical products of heating chlorinated hydrocarbons in welding conditions.