Abstract:
Local Exhaust Ventilation (LEV) systems are commonly used to prevent exposure to harmful fumes generated by welding operations. Welding processes are hazardous activities that pose a unique combination of both safety and health risks to more than 500,000 workers nationwide in a wide variety of industries. Welders are expoed to fumed containing different gases and metal aprticles, depending on the composition of the welding electrodes, welded material, welding method, welding position, ventilation system, and the use of respiratory protective devices.
Airborne concentrations of metal fumes generated by welding activities can be reduced with the use of Local Exhaust Ventilation (LEV), a mechanical system that draws fumes away from the welders' breathing zone. This is the preferred method to capture airborne contaminants at their source thereby potentially reducing or even eliminating the need for respiratory protective devices. The primary goal of this study was to evaluate the effectiveness of two commercially available portable LEV systems.
The two LEV systems evaluated in this study were a welding gun with a built-in fume extraction system connected to portable vaccuum, and a portable vaccuum with a small, bell-shaped hood connected to the exhaust system by a flexible hose. Two of the most common types of welding (Gas Metal Arc and FLux Core Arc Welding) were conducted by three apprentice welders using three different ventilation conditions (gun-mounted fume extractor, worker-positioned extractor, and no ventilation) in 3 different welding postions (horizontal, vertical, flat, and overhead). Worker exposure to welding particulate was recorded by real-time personal particulate monitor.
Results of this study showed that LEV systems were effective only if certain conditions were met. LEV effectiveness depends on several variables including its proximity to the welding operation. To be most effective, the distance between the hood and the source of fumes should be no more than two duct diameters. Howver, maintaining a close proximity to the weld is not always feasible. The effectiveness of the gun-mounted fume extractor was related to the welding position. Additional determinants, such as welder's body position and welding type, also influence the effectiveness of LEV systems.