A Good Seal
Why Respirator Fit Testing Is Essential for Filtering
Facepiece Respirators
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Certain activities that directly involve workers will always require respiratory protection. These activities include firefighting, abrasive blasting, and various construction work, among others. The testing and approval of respirators for their intended uses is conducted by NIOSH according to its 1995 final rule on respiratory protective devices (42 Code of Federal Regulations Part 84). Where respirators are mandatory, OSHA’s respiratory protection standard requires a respiratory protection program that includes fit testing of employees to verify the respirator can achieve the requisite seal with the wearer’s face. This is necessary for the wearer to achieve the assigned level of protection against the workplace inhalation hazards for which the respirator is designed and approved. Respirators are intended to provide adequate protection against airborne contaminants when the employer implements an OSHA-compliant respirator program, which includes requirements for training, fit testing, use, and maintenance. Respirators that are not properly selected, used, or maintained can result in a significant reduction in protection in industrial or healthcare settings. Employers and employees may consider fit testing to be burdensome and time-consuming, robbing time from vital work. However, successfully passing a fit test is necessary to verify that the wearer can properly don and position the respirator. Failure to have an acceptable respiratory protection program in place can needlessly expose the wearer to airborne particle exposures. FILTER EFFICIENCY The term “filter efficiency” describes the effectiveness of a filter to prevent penetration of particles. However, the term is meaningless unless the conditions under which efficiency is measured are identified. This point is conveyed by a memorable analogy that appeared in a 1940 U.S. Bureau of Mines report: “Chicken wire is 100 per cent efficient against chickens, but not against sparrows.” NIOSH certification testing uses aerosols of the most penetrating particle size at high air velocity rates. Particle sizes of aerosols in most workplaces are generally larger and captured with even greater efficiency. In addition, typical worker breathing rates are lower than those used during NIOSH filter certification testing. Thus, filter efficiency will be higher in the workplace than that measured during NIOSH approval tests. Furthermore, in most workplaces, filter efficiency increases as particulates are collected by the filter. Wearers need to be concerned about being properly fitted using an OSHA-accepted fit-test method, using the respirator when required, and using it in a manner consistent with its instructions. If the NIOSH-approved respirator has the correct filter, the primary concern is the fit of the respirator to the wearer’s face to reduce airborne particle exposure. RESPIRATOR FIT Respirators are often described as “well-fitting,” “having a tight seal,” and “snug.” These terms are well intended but meaningless regarding the protection afforded by the respirator unless a respirator of a specific make, model, style, and size is fit tested to the individual wearer. (See the sidebar for an explanation of OSHA’s “fit factor.”)
OSHA’s Fit Factor, Explained OSHA regulations define acceptable methods for fit testing. The fit test requires a minimum fit, described as a fit factor. Essentially, the fit factor is a measure of the respirator seal to a wearer’s face. When a wearer fails to achieve the required fit factor in the fit test—that is, when the leakage around the respirator seal is greater than the allowable level—the wearer will likely not attain the expected level of protection provided by the respirator class.
Upon a fit test failure, the individual being fit tested must continue trying different respirator models, sizes, or both until they successfully pass the fit test. If a wearer cannot pass a fit test with any tight-fitting facepiece, one option is a loose-fitting powered air-purifying respirator (PAPR), which provides a continuous flow of filtered air to the wearer. Since a loose-fitting PAPR does not require tight sealing surfaces, fit testing is not needed. Reassignment to a job that doesn’t require respiratory protection is another option for wearers who cannot pass a fit test.
Never try to force-fit the same respirator. If a fit test is not performed, the level of protection is unknown.
THE VALUE OF FIT TESTING For more than 50 years, research studies have been performed to determine workplace and simulated-workplace measurements of respiratory protection. These studies formed the basis for establishing protection factors specified in national consensus standards. In 2006, OSHA issued a final rule that defined these “assigned protection factor” (APF) regulations. APFs are the expected level of protection for a respirator class when used in an OSHA-compliant respiratory protection program (RPP). Fit testing is a required element of an OSHA-compliant RPP. If the wearer is not provided the same make, model, style, and size respirator with which they are fit tested, the protection provided by the wearer’s respirator is uncertain.
The significance of fit testing was demonstrated in a simulated workplace protection factor study published in the Journal of Occupational and Environmental Hygiene in 2007. Researchers assessed 15 models of NIOSH-approved, half-facepiece elastomeric respirators equipped with N95 filters, 15 models of NIOSH-approved N95 filtering-facepiece respirators, and 6 models of surgical masks. Test results revealed that passing fit testing resulted in the respirators providing the expected level of respiratory protection—that is, achieving an APF of 10 for half-facepiece respirators—whereas without fit testing, all respirators provided less than half of the expected level of protection from inhalation hazards. The study found that surgical masks did not provide any significant level of protection.
Currently the only means to assess the expected level of protection for the unique combination of wearer and respirator is the wearer passing a respirator fit test. Without a fit test, the respirator cannot be expected to provide the wearer with the level of protection predicted by the APF of the respirator class.
Figure 1. Quantitative respirator fit testing of an N95 filtering facepiece respirator. Image copyrighted by and courtesy of TSI Inc.
When OSHA was developing its respiratory protection standard, the agency sought information on fit-testing practices from multiple stakeholders. OSHA’s assessment of this information was incorporated into the preamble of the standard, which states, “Individuals with poorly fitting respirators were often detected only through fit testing, and not by other methods such as observation of changes in facepiece fit, failure to pass a user seal check, or an employee reporting problems with the fit of the respirator.”
The 1998 report “Fit Testing and Use of Negative Pressure Respirators for Protecting Military Personnel Against Chemical Warfare Agents” by Roy T. McKay identifies the following reasons for fit testing:
• Fit testing can identify poorly-fitting respirators that will not provide adequate protection due to face seal leakage.
• Fit testing has been successfully used to identify defective respirators that were not identified during routine inspection by the user.
• Perhaps the most beneficial aspect of fit testing respirator wearers is the training opportunity it provides. Fit testing is one of the rare situations that permits an individual to have personalized training. During fit testing, the respirator wearer can have their respirator inspected by the fit test operator, who has had more experience inspecting respirators. The operator can observe respirator donning and user seal-check techniques, identify deficiencies, and make recommendations. The operator can also provide insight not generally available in a classroom training session. For example, the process of fit testing respirators can provide a level of training not generally appreciated, especially when fit testing is used to help select a better-fitting respirator. In addition, positive feedback during respirator donning as part of a fit test may be vital to determine whether the respirator is donned correctly in the workplace.
• The ability to practice donning procedures while simultaneously conducting a fit test is a valuable training tool. Individuals who practice respirator donning without access to fit testing—that is, in the absence of any feedback—may simply reinforce improper donning techniques. Feedback should be provided to every respirator wearer and is considered an indispensable part of an effective respirator training program.
• In the industrial environment, the fit test is often used as the final exam to assess the wearer’s ability to don the respirator without any assistance and then subsequently pass the fit test. When used in this fashion, the fit test provides a method to evaluate the user’s understanding of information provided during respirator training and their ability to properly don the respirator and adjust the straps without any assistance.
When a fit test is administered, it must be done correctly. A poorly fitting respirator can pass both quantitative and qualitative fit tests if the tests are administered incorrectly. For an explanation of common fit testing errors and solutions, watch the video of McKay’s presentation to the Canadian Aerosol Transmission Coalition on YouTube. Another useful resource is “Understanding Filtration Efficiency Testing and Fit Testing in Filtering Facepiece Respirators (FFRs),” an informative fact sheet on fit testing available from the NIOSH National Personal Protection Technology Laboratory.
RICHARD W. METZLER, MSIE, is former director of NIOSH/NPPTL and chaired the ANSI/ASSE Z88.2 subcommittee.
DAVID L. SPELCE, MS, CIH (1997–2015), served as the Navy’s respirator expert from 1987 to 2015.
JAMES S. JOHNSON, PhD, CIH, QEP, is chair of ASTM subcommittee F23.65 on respiratory protection.
CHRISTOPHER C. COFFEY, PhD, is the former associate director for science (retired) of NPPTL.
TIMOTHY R. REHAK, PE, is a retired general engineer with the NPPTL Respirator Approval Program.
ROY T. MCKAY, PhD, is past chair for ANSA/AIHA Z88.10, Respirator Fit Test Methods.
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Bureau of Mines: “Testing Respiratory Protective Equipment for Approval” (August 1940).
Journal of Occupational and Environmental Hygiene: “Simulated Workplace Protection Factors for Half-Facepiece Respiratory Protective Devices” (June 2007).
NIOSH: “42 CFR Part 84 Approval of Respiratory Protective Devices” (June 1995).
NIOSH: “Understanding Filtration Efficiency Testing and Fit Testing in Filtering Facepiece Respirators (FFRs)” (2021).
Occupational Health Clinics for Ontario Workers: “Common Respirator Fit Testing Errors and Solutions” (presentation by Roy T. McKay, October 2022).
OSHA: Assigned Protection Factors Final Rule, 29 CFR Parts 1910, 1915, and 1926 (PDF, August 2006).
OSHA: Respiratory Protection, 29 CFR Parts 1910 and 1926 (January 1998).
University of Cincinnati: “Fit Testing and Use of Negative Pressure Respirators for Protecting Military Personnel Against Chemical Warfare Agents,” Report for NAVSEA (1998).