Two-zone model application to breathing zone and area welding fume concentration data

Area of Science:

• Occupational hygiene and environmental science.
• Industrial safety and health engineering.
• Air quality monitoring and exposure assessment.

Background:

• Shielded metal arc welding (SMAW) generates hazardous fumes, necessitating accurate exposure assessment.
• Existing welding fume generation rates are often derived from laboratory settings, potentially not reflecting real-world conditions.
• The two-zone model is a tool for estimating contaminant concentrations in ventilated spaces.

Purpose of the Study:

• To determine field-derived personal exposure emission (generation) rates for welding fume during actual pipefitter work.
• To apply the two-zone model using field data to assess welding fume concentrations.
• To compare field-derived generation rates with existing laboratory-derived values.

Main Methods:

• A professional pipefitter/welder performed SMAW on carbon steel under field conditions (boiler room and breezeway).
• Breathing zone and area air samples were collected and analyzed for total particulate (TP), iron (Fe), and manganese (Mn).
• The steady-state two-zone model was applied to the collected air concentration data.

Main Results:

• Field-derived welding fume generation rates for TP, Fe, and Mn were significantly lower than published laboratory values.
• Boiler room and breezeway personal breathing zone concentrations for TP, Fe, and Mn were quantified.
• The two-zone model effectively described personal breathing zone and area sample concentrations.

Conclusions:

• Field-derived welding fume generation rates are crucial for accurate occupational exposure assessments.
• The two-zone model can be utilized with field data to estimate welding fume exposures in industrial settings.
• This study highlights the importance of site-specific data for industrial hygienists.