Effects of voltage and wire feed speed on weld fume characteristics.

Welding generates high concentrations of ultrafine particles, which research suggests may be more toxic than larger particles. Fume characteristics were measured in a controlled apparatus as a function of voltage level and wire feed speed. Particles were sampled close to the welding process on mixed cellulose ester membrane filters and analyzed for iron, manganese, and total particulate matter at an accredited industrial hygiene laboratory. An ultrafine condensation particle counter measured the particle number concentration, and an optical particle counter measured the particle size distribution. Submicrometer particle number concentrations and iron, manganese, and total particle mass concentrations all depended on voltage levels but not on wire feed speed at a constant voltage. Ultrafine particle concentrations were more than three times greater at 23.5 V than at 16 V. Particles 0.5-0.7 microm in diameter counted by the optical particle counter increased from 9800 particles/cm(3) at 16 V to 82,800 particles/cm(3) at 23.5 V. Manganese concentration was 1.7 mg/m(3) at 16 V vs. 6.4 mg/m(3) at 23.5 V. The data suggest that welders should use lower voltage levels whenever possible.