Control of exposure to welding fumes by ventilation and helmet pressurisation.

Occupational hygiene conditions were examined in a welding shop after repairing the air-handling unit. Good indoor air quality was achieved with the new replacement ventilation system. The airborne dust concentrations varied from the detection limit of 0.1 mg/m3 to 0.8 mg/m3 at the stationary sites. Even the breathing zone concentrations of the welders remained below or equal to 2.1 mg/m3. The concentrations of carbon monoxide did not exceed the level of 1 cm3/m3. In addition to the good efficiency of replacement ventilation during mild winter conditions, the local exhaust ventilation proved to be even more significant than pressurisation of helmets in decreasing the dust exposure of welders and other workers exposed due to dust distribution in the welding shop.