October 28, 2008
A little more than a year after implementing stricter hexavalent chromium standards to the metalworking industry, OSHA has gone a step further and released respirator fit testing guidelines to complement the existing standard.
Fabricators may be required to use respirators to protect themselves from inhaling fumes, particles, or dust when performing cutting, grinding, welding, coating, or painting, especially if they are in contact with chrome-containing stainless steel or coatings, which presents the risk of hexavalent chromium exposure.
In cases such as these, respirators must be provided to protect the health of a worker and be selected on the basis of hazards the worker is exposed to. Employers are responsible for establishing and maintaining an effective respiratory protection program, which includes fit-testing for all employees who are required to use one.
The Occupational Safety and Health Administration (OSHA) is looking at fit-testing again, this time with a proposal to add a new fit-test method to its existing standard. The following is a review of the current requirements.
Anyone using a negative- or positive-pressure, tight-fitting facepiece respirator must pass an appropriate fit-test that uses an OSHA-accepted protocol. Fit-testing is required before initial use, whenever a different respirator facepiece is used, and at least once a year thereafter. An additional fit-test is required whenever a change in the wearer's physical condition, such as facial scarring, dental changes, cosmetic surgery, or a significant change in body weight, could affect respirator fit.
A few basic checks must be performed even before using test protocols. The wearer should check for proper chin placement and strap tension, but be sure not to overtighten the respirator. He should make sure it fits correctly across the nose bridge—a respirator should span the distance from nose to chin—and that it doesn't slip. Along with evaluating fit and respirator position, the wearer also should perform a seal check. If leakage is detected from a poorly fitting facepiece, he needs to try another size of the same model, or another model of respirator.
The workplace exposure level determines what constitutes an acceptable fit and which OSHA fit-test procedure is required. The two types of fit-test methods are qualitative and quantitative.
Qualitative methods rely on a subjective sensation, such as taste, irritation, or smell, to a particular test agent. These test agents include isoamyl acetate, saccharin, Bitrex®, and irritant smoke. Essentially, the wearer puts on the respirator and enters a test chamber. The test agent is then released, and the wearer must determine whether or not he can smell, taste, or feel the agent inside of the respirator during a series of defined exercises.
Quantitative methods use instruments to measure face seal leakage. These protocols are more complex and thorough because they are not dependent on the wearer observing and reporting the presence of a test agent. These protocols are:
1. Aerosol generated from corn oil, salt, or DEH: The wearer enters a test chamber that is isolated from the outside air. A sampling port or probe is inserted into the respirator, and an instrument is used to create a computer record or strip chart showing the rise and fall of the test agent concentration with each inhalation and exhalation. Whenever the concentration inside the mask exceeds 5 percent for half masks, and 1 percent for full-facepiece respirators, the test subject must be refitted and retested. The fit factor is determined by the ratio of the average chamber concentration to the concentration measured inside the respirator for a series of test exercises.
2. Condensation nuclei counter (PortaCount™). This protocol uses a probe with a special sampling device installed on the respirator that samples the air from inside the mask. A probed respirator is required for each make, style, model, and size that the employer uses. These can be obtained from the respirator manufacturer or distributor. Alternatively, the manufacturer also provides probe attachments (TSI sampling adapters) that permit fit-testing in an employee's own respirator. A record of the test needs to be kept on file, assuming the fit-test was successful.
3. Controlled negative pressure (Dynatech FitTester 3000). This protocol measures leak rates through the facepiece of negative-pressure respirators. To perform the test, the subject closes his mouth and holds his breath, after which an air pump removes air from the respirator facepiece. The facepiece fit is the leak rate through the facepiece, expressed as milliliters per minute. CNP systems have built-in capability to conduct fit-testing that is specific to a work rate, mask, or gender.
For negative-air-pressure purifying respirators, users may rely on either a qualitative or a quantitative fit-test procedure for exposure levels less than 10 times the occupational exposure limit. An exposure level greater than 10 times the occupational exposure limit requires a quantitative fit-test procedure. Requirements for respirators used to protect wearers from certain airborne contaminants, such as asbestos, have their own special fit-test requirements.
OSHA's current proposal is to include an abbreviated Bitrex qualitative fit-test in its respiratory protection program. This emphasizes that OSHA is again focusing on protection programs in workplaces where respirators are required to ensure employee safety and health.
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