Ozone: a critical contaminant produced during gas metal arc welding (GMAW) on aluminum alloysresolving the short- versus long-duration sampling discrepancy

Ozone is one of the gases produced during argon-shielded arc welding on aluminum alloys. Arc welding superimposes multiple episodes of intense emission of short duration onto the background level during the work shift. Short-duration exposures during welding were measured using colorimetric detector tubes and long-duration exposures, by colorimetric badges utilizing similar chemistry. Both devices were positioned on the lapel in the breathing zone. Many of the short-duration samples exceeded the 8-h TLV-TWA (threshold limit value-time-weighted average) of 0.08ppm for moderate work during argon-shielded gas metal arc welding (GMAW) also known as metal inert gas (MIG) welding. Some short-duration samples exceeded the transient limit of 0.24ppm (3x the TLV-TWA), and several exceeded the maximum of 0.40ppm (5x the TLV-TWA). Exceedance of the maximum in jurisdictions using TLVs as exposure limits necessitates control measures including effective local exhaust ventilation and respiratory protection. Ozone was undetectable (<0.04ppm) during gas tungsten arc welding (GTAW) also known as tungsten inert gas (TIG) welding. During long-duration sampling, almost all levels during GMAW were 0.08ppmh (0.01ppm averaged over 8h), the limit of detection of the sampling device. As a result, ozone is a critical gaseous contaminant (requiring control measures) during GMAW (MIG welding). Protection of the eyes against irritation in sensitive individuals dominates other considerations.