How your workplace conditions, process affect your choice
August 29, 2002
Selecting the right respirator for a welder involves examining the processes used, the workplace environment, and the types of base metal and consumables used. This article offers tips for finding the right respirator for your application, preferences, and workplace.
When you ask a safety or health practitioner to recommend a welding respirator, be prepared to answer at least a dozen questions first.
The first concern in selecting an appropriate respirator is the process contaminants. The base metal and consumables generally determine the air contaminant. Material safety data sheets (MSDS) and a description of the composition of the base metal and electrodes can help you identify which contaminants may be present.
In general, the most significant contaminant from shielded metal arc welding (SMAW) mild steel is iron oxide fumes. Overexposure to copper or manganese fumes is possible during gas metal arc welding (GMAW) with copper-coated wire or if manganese is a component of the base metal or consumable.
While both operations also may generate gaseous contaminants such as ozone and oxides of nitrogen, overexposure generally isn't a problem in open work environments. Gaseous contaminants are dispersed readily by normal air currents or general ventilation.
Welding painted or galvanized surfaces or alloys such as stainless steel creates additional toxic contaminants, including zinc oxide, chromium, and nickel. Figure 1lists potential contaminants generated by welding operations and a summary of their health effects.
Next, measure the concentration of the contaminants. Evaluating the potential for high contaminant exposures involves observing the work environment. An open environment with good general or local exhaust ventilation presents less exposure risk than corners or other confined areas. Note that welding in permit-required confined spaces requires special procedures and extreme caution.
Intermittent welding is less likely to overexpose you than production welding. Collecting air samples in your breathing zone can be a reliable way to determine exposures. This typically involves using personal sampling pumps to draw the workroom air through filters and analyzing them. Guidance for performing this kind of sampling is available in American Welding Society (AWS) standard F1.1 and the Occupational Safety and Health Administration's (OSHA's) Technical Manual. Safety and health consultants and many insurance companies can assist with air sampling.
The results then are compared with the permissible exposure limit (PEL) or threshold limit value (TLV) for the contaminants sampled. PELs represent the amount of air contamination legally permissible according to OSHA. TLVs represent advisory exposure limits published by the American Conference of Governmental Industrial Hygienists.
Dividing the measured exposure by the appropriate exposure limit gives a value known as a hazard ratio. The hazard ratio defines the level of respiratory protection required.
A value less than 1 means you legally don't have to use a respirator. A value between 1 and 10 demands at least a half-facepiece respirator, and a value between 10 and 50 means a full facepiece is the minimum acceptable.
Higher levels of protection, such as powered air-purifying respirators (PAPR), must be used for exposures greater than 50 times the exposure limit. Any respirator is considered an interim measure or a last-resort control for air contaminant exposures. Good industrial hygiene practices and OSHA regulations dictate that exposures be reduced to acceptable levels with additional ventilation; changes in work practices; or other, more permanent means.
Because the majority of overexposures involve fumes only, select an appropriate particulate filter if you need to use an air-purifying respirator.
The National Institute for Occupational Safety and Health (NIOSH) certifies three series of filters for half- and full-facepiece air-purifying respirators. NIOSH identifies these filters as N (not resistant to oil), R (oil resistant), and P (oilproof), and each is available in 95, 99, and 99.97 percent efficiencies.
In most welding situations, the appropriate filter is a class N95. Use an R95 or P95 if airborne oil mist is present. Class 100 filters are necessary only if specified by a substance-specific OSHA regulation, such as the cadmium or lead standard.
After choosing the appropriate respirator facepiece and filter type, consider the specific respirator features you want for your particular workplace. Both reusable and disposable respirators are available. Examine advantages and disadvantages for compatibility with your workplace conditions, your preferences, and company management policies. Some filters have heat and spark resistance or special loading characteristics for fumes. Others are treated with a small amount of activated carbon to remove nuisance levels of odorous contaminants below PEL levels.
Finally, use any respirator as part of a comprehensive respiratory protection program as described in OSHA regulation 29 CFR 1910.134. Your program should include procedures for worker training and fit testing, medical evaluation, respirator use and maintenance, and program evaluation. Using a properly selected respirator can help ensure a healthy work environment for you.
American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126-5671, Web site www.aws.org.
National Institute for Occupational Safety and Health, 200 Independence Ave. S.W., Washington, DC 20201, Web site www.cdc.gov/niosh.
Occupational Safety and Health Administration, 200 Constitution Ave. N.W., Washington, DC 20210, Web site www.osha.gov.