Engineering Controls Database
Welding Operations: Local Exhaust Ventilation Systems
|
Welding operations produce gaseous and aerosol by-products composed of a complex array of metals, metal oxides, and other chemical species volatilized from either the base metal, the welding electrode, or the flux material. The effect of welding fumes and gases on a welder’s health can vary depending on such factors as the length and intensity of the exposure, and the specific toxic metals involved. Welding processes involving stainless steel, cadmium – or lead-coated steel, or metals such as nickel, chrome, zinc, and copper are particularly hazardous as the fumes produced are considerably more toxic than those encountered when welding mild steel. Mild steel consists mainly of iron, carbon, and small amounts of manganese, phosphorous, sulfur, and silicon, while stainless steel contains mainly iron, chromium, nickel, titanium, and manganese. The NIOSH criteria document identifies arsenic, beryllium, cadmium, chromium (IV), and nickel as potential human carcinogens that may be present in welding fumes |
|
| Census data indicates that over 700,000 workers in the United States are involved in welding or allied processes. Animal and epidemiological studies suggest that welding is associated with a wide range of adverse health effects such as metal fume fever (with symptoms resembling the flu), pneumonitis, chronic bronchitis, and decrements in pulmonary function. A large body of evidence suggests that welders have a 40% increase in relative risk of developing lung cancer as a result of their work. Other cancers associated with welding include leukemia, cancer of the stomach, brain, nasal sinus, and pancreas. Welding processes are known to generate aerosols with a significant fraction in the nanometer size range. Recent research also has indicated that particles in the nanometer size range may have adverse health effects. Other health hazards during welding can include vision problems and dermatitis arising from ultraviolet radiation exposures, burns, and musculoskeletal stress from awkward working positions. | |
Two portable local exhaust ventilation units were evaluated. One, MEF, was a mobile, wheeled fume extractor unit with a 2 meter flexible arm. The other, BSFM-2101, was a portable fan unit on a support stand with a flexible arm. The workers place the portable LEV unit near the welding spot so as to best capture the welding fumes. Neither of the local exhaust ventilation units was equipped with filters during the study. Instead, the captured fumes were exhausted via flex-duct to a point outside the welding area.   |
|
| 214-11-A; 214-12-A; 214-13-A; 214-15-A; | |
|
gas metal arc welding gas tungsten arc welding metal worker shielded metal arc welding welder welding |
|
| Without LEV, total welding fume concentrations ranged from 2 to 60 mg/m3 of air. Ventilation cut the fumes to 3 to 13 mg/m3. |