August 8, 2002
Welding smoke and fumes can be dangerous, but there are several types of equipment designed to clean the air welders breathe. Capturing airborne pollutants at the welding source is the most effective technique available. Common designs include source capture arms, portable source capture air cleaners, downdraft or sidedraft tables, and smoke extraction systems. Other air purification devices include ambiant air capture systems and breathing masks and respirators.
Every company dreads indoor pollution problems: the visit from an Occupational Health and Safety Administration (OSHA) inspector, the call from a former employee's attorney requesting damages, the loss in production when an employee goes home sick from welding fumes. All of these problems cost the company money and add stress, but they can be avoided.
An estimated 562,000 workers are at risk for exposure to chemical and physical hazards while welding, cutting, and brazing, according to OSHA (www.osha.gov). Welding smoke and fumes are among the leading causes of welding injuries. A typical welder can inhale a number of harmful substances, each with the potential to harm his health and a company's bottom line.
Just a few examples of pollutants that are common in welding smoke are chromium, manganese, ozone, nickel, arsenic, asbestos, silica, cadmium, nitrogen oxides, cobalt, phosgene, beryllium, acrolein, fluorine compounds, selenium, carbon monoxide, copper, lead, and zinc.
Exposure to these substances can cause various illnesses. One of the most common is metal fume fever, which is caused by zinc, magnesium, copper, and copper oxide fumes. According to the National Institute for Occupational Safety and Health (NIOSH, www.cdc.gov/niosh/homepage.html), it has been estimated that 30 to 40 percent of all welders have experienced metal fume fever at some time.
Symptoms may include chills, thirst, fever, muscle ache, chest soreness, coughing, wheezing, fatigue, nausea, and a metallic taste in the mouth. Figure 1 shows other welding fume hazards.
It's no wonder that OSHA has taken an interest in welding and developed Standard 29 CFR 1910. However, equipment has been designed to help keep employees healthy and companies compliant with OSHA regulations.
Capturing airborne pollutants at the welding source is the most effective technique available for reducing welders' exposure to fumes. Common designs include source-capture arms, portable source-capture air cleaners, downdraft or sidedraft tables, and smoke extraction systems.
Source-capture Arms. Source-capture arms typically are connected to fixed air cleaners via ducting. Often a worker can change the position of the arm for convenience. Some arms have lighted hoods for better visibility, motorized movement for easier positioning, and are available in a variety of lengths and diameters to suit the application. Some are as long as 28 feet.
Portable Source-capture Air Cleaners. An air cleaner and an arm rolled into one unit, portable source-capture air cleaners can be rolled from workstation to workstation and positioned in the same ways that a source-capture arm is positioned. Recently a new portable cleaner was introduced on which air cleaning attachments can be switched much like a home vacuum cleaner. Such attachments include a single arm; dual arms for two workstations; a downdraft table; a backdraft hood; and a long, flexible hose with a hood (see Figure 2).
A new type of portable source-capture air cleaner can use attachments such as a single arm (a) and a downdraft table (b).
Downdraft Tables. The downdraft table serves as both a workbench and an air cleaner. A rigid grill supports the work, while an air cleaner below draws smoke and fumes down and away from the worker. A worker can weld, grind, and cut on the same table.
Sidedraft Tables. Similar to the downdraft table, the sidedraft table's draft hood is mounted at the same level as the workpiece, pulling pollutants to the side and away from the worker.
Smoke Extraction Systems. These systems use extraction-type welding guns equipped with an air inlet nozzle that, when connected to a smoke extraction air cleaner, captures fumes generated as the weld is laid (see Figure 3).
Ambient systems are popular and generally do a good job of cleaning the ambient air in a plant. This method consists of several air cleaners in a racetrack air pattern that scrub the desired area and direct the fumes to air cleaners.
Smoke extraction air cleaners extract fumes at the gun.
Typically, 10 ft. from the floor is an ideal mounting height for ambient-air cleaners. A minimum of eight air changes per hour (ACH) is recommended. In heavy-fume applications, 10 to 12 ACH are appropriate. These systems are best used in addition to source-capture equipment, not as a replacement.
Respirators and masks also help to shield workers' lungs from hazardous fumes. Available in many capacities, filter media, and configurations, masks should supplement ventilation equipment. The drawback of masks is that workers think they are uncomfortable and inconvenient and sometimes refuse to use them at all.
While plant and shop managers and owners continually look for new ways to increase production and decrease cost, protecting employees often ranks low on the priority list. However, employee safety is one of the keys to achieving both goals—by working to keep employees healthy and more focused on their work, a company can more easily avoid common production pitfalls such as employee downtime, OSHA noncompliance, and lawsuits.
Jerold Jay is a design engineer for the Micro Air® product line manufactured by Metal-Fab Inc., P.O. Box 1138, Wichita, KS 67201, phone 316-943-2351, fax 316-943-2717, e-mail email@example.com, Web site www.microaironline.com. The Micro Air line includes source-capture units, ambient-air cleaners, dust collectors, and mist collectors for welding and metal processing applications.
Providing safety-related information such as that found in this article is one of the goals of the FMA/CNA Safety Committee. The committee comprises representatives of the Fabricators & Manufacturers Association, International (FMA); Norman-Spencer, Inc.; and CNA. The Safety Committee provides information and assistance to improve workplace safety and the manufacturing environment. For information, call FMA's customer service department at 815-399-8775
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