New NIOSH Study Supports the OSHA Annual Fit Testing Requirements for Filtering Facepiece Respirators

Posted on by Ziqing Zhuang, PhD; Michael Bergman, MS; and Jaclyn Krah, MA


circle head 4Results of a recently completed NIOSH study confirm the necessity of the current Occupational Safety and Health Administration (OSHA) respirator fit testing requirement, both annually and when physical changes have occurred. The study’s conclusions emphasize that respirator users who have lost more than 20 pounds should be re-tested to be sure that the current size and model of respirator in use still properly fits. For over three years, NIOSH researchers followed a cohort of 229 subjects measuring N95 filtering facepiece respirator (FFR) fit and physical characteristics (e.g., face size, weight) every six months.  Prior to this study, very little research existed looking at the relationship between respirator fit over an extensive period of time and the change in facial dimensions, as could be caused by weight gain or loss. OSHA requires FFR users to undergo an annual fit test, which is vital to ensuring continued proper respirator fit. In addition to annual fit testing, OSHA requires that fit testing be repeated “whenever an employee reports, or the employer or the physician or other licensed health care professional makes visual observations of changes in the employee’s physical condition that could affect respirator fit (e.g. facial scarring, dental changes, cosmetic surgery, or an obvious change in body weight.” (OSHA, 1998)


The appropriate length of time between respirator fit tests has been a point of debate and discussion for many years. Fit testing can be time-consuming and a burden to workplace resources (Zhuang, 2015). OSHA addressed these concerns in 1998 when publishing the respiratory protection standard (OSHA, 1998). During the public comment period for OSHA’s rulemaking, data from four companies were considered in establishing the annual fit test requirement.  Three of the companies reported <3% of employees failed fit testing after 1 year and one company conducting biannual fit tests found that 7% of their employees switched to different sizes or models because of a failed fit test.  OSHA considered a two-year 7% failure rate unacceptable (meaning that a high percentage of employees could be relying on poor-fitting respirators if not fit tested annually), and thus supported an annual fit testing requirement (OSHA, 1998).

In 1999, NIOSH endorsed all provisions of OSHA’s 29 CFR Part 1910.134 relating to the frequency of fit testing (NIOSH).  Despite this endorsement, questions surrounding the frequency of respirator fit testing remained from employers (e.g., especially those in the healthcare sector) and the industrial hygiene community. Examples are located in the comments to a previous NIOSH science blog on this topic titled Frequency of Respirator Fit Testing. In response to these continued concerns, NIOSH initiated a study to address three primary questions:

  1. Does respirator fit change over time?
  2. Does weight change cause respirator fit change?
  3. Is annual fit testing necessary?

NIOSH conducted a pilot study of 10 subjects to investigate the variation in fit test data to assess the background failure rate. The subjects were tested in order to match them with a properly-fitted respirator.  The subjects repeated the tests two and four weeks after the initial tests.  Adequate fit was maintained for all 10 subjects during this time period. After conducting this pilot study, researchers were ready for the three-year large scale study that would examine the link between how often someone is fit tested and the changes in N95 FFR fit when weight fluctuation occurs and alters facial dimensions. More detailed background information for reporting of this pilot study can be found in a previous NIOSH Science Blog titled Frequency of Respirator Fit Testing and in the manuscript published in the Journal of Occupational and Environmental Hygiene (Zhuang et al., 2011). 

The Study

Subjects were recruited from a group of study volunteers used for certification testing and physiology studies, as well as from the general public in southwestern Pennsylvania.

Researchers focused on FFRs because they are the most commonly-worn respirator used in the healthcare industry and the necessity of annual fit testing for these types of respirators is often debated. The study included seven different sizes and models of N95 FFRs, all of which were purchased for the CDC Strategic National Stockpile at the time the study was initiated.

The researchers were interested in measuring the fit factor, which tells the researcher whether a respirator fits the subject properly or not.  Subjects qualified for the study by demonstrating acceptable fit for one of the N95 FFR models in the study.  They then used samples from that same FFR model for the remainder of the study.  Fit factors from nine donnings (putting on the respirator) were measured and physical characteristics of the subjects were captured approximately every 6 months for a 3-year period.

The Results

Of the 229 subjects that initially enrolled in the study, 134 completed all seven visits. Data was omitted for subjects who participated in only the first visit, leaving 195 subjects who participated in two or more visits. Subjects were categorized by face length and width and the researchers determined that the distribution of facial dimensions of the 195 participants were a good representation of the general U.S. workforce (Zhuang, 2007 & Zhuang 2005).

The estimated percent of workers whose respirator did not fit them increased with increasing length of time between fit tests, from 10% at Year 1 to 20% at Year 2, doubling those at risk for exposure if not fit tested, and to 26% at Year 3. This exceeds the 7% threshold used by OSHA in 1998 during rulemaking. Additionally, twenty-four percent of subjects who lost more than 20 pounds no longer maintained an acceptable fit.


This study found that respirator fit did change over time. The greater the weight loss, the higher the chance that respirator fit will change. Therefore, this NIOSH study supports the current OSHA requirement for annual fit testing. Additionally, respirator users who lose more than 20 pounds since his or her last fit test should prioritize scheduling a fit test to ensure proper respirator fit. Though further research is necessary, because of the similarity in face seal between other tight-fitting respirators and FFRs, these findings may be applicable not only to FFRs but also to other tight-fitting respirators. The full NIOSH study titled, “Temporal Changes in Filtering-Facepiece Respirator Fit”, is published in the Journal of Occupational and Environmental Hygiene and can be accessed through Taylor & Francis Online.


Dr. Zhuang is the Material and Equipment Performance Team Leader in the Research Branch at the NIOSH National Personal Protective Technology Laboratory (NPPTL).

Mr. Bergman is an Associate Service Fellow in the Research Branch at the NIOSH National Personal Protective Technology Laboratory

Ms. Krah is a Health Communication Specialist in the NIOSH National Personal Protective Technology Laboratory.



U.S. Occupational Safety and Health Administration: Respiratory Protection, 29 CFR 1910.134: Final rule. Federal Register Notice. 63:1152-1300 (1998).

Zhuang, Z., M. Bergman, E. Brochu, A. Palmiero, G. Niezgoda, X. He, R. Roberge, and R.E. Shaffer: Temporal Changes in Filtering Facepiece Respirator Fit. JOEH. 2015 (ePub ahead a print, DOI: 10.1080/15459624.2015.1116692).

U.S. Institute of Medicine: Assessment of the NIOSH Head-and-Face Anthropometric Survey of U.S. Respirator Users. Washington, DC: The National Academies Press, 2007

Zhuang, Z., Benson, S., Lynch, S., Palmiero, A., & Roberge, R. (2011). Laboratory study to assess causative factors affecting temporal changes in filtering facepiece respirator fit: Part I–pilot study. Journal of occupational and environmental hygiene, 8(12), 729-739.

Zhuang, Z.Q., B. Bradtmiller, and R.E. Shaffer: New Respirator fit test panels representing the current US civilian work force. J. Occup. Environ. Hyg. 4(9): 647-659 (2007).

Zhuang, Z.Q. and B. Bradtmiller: Head-and-face anthropometric survey of US respirator users. J. Occup. Environ. Hyg. 2(11): 567-576 (2005).

NIOSH [1999]. NIOSH Policy Statement: NIOSH Respirator Use Policy/OSHA’s I91 0.1 34. August 4, 1999.



Posted on by Ziqing Zhuang, PhD; Michael Bergman, MS; and Jaclyn Krah, MA

14 comments on “New NIOSH Study Supports the OSHA Annual Fit Testing Requirements for Filtering Facepiece Respirators”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    Relevant and well anticipated through monitoring and survelience from all industrial sectors to provide the betterment towards maintaining healthy personnel in mana- ging the realistic PPE towards their performances; by constantly retrieving the datas via audits.

    This is a great study to support the Health Care Industry. As stated,” further research is necessary.” Are there plans to do a study on full face air purifying respirators (APR)? Their sealing surfaces and material composition differ greatly from the N95. Thanks.

    Yes. Respirators, such as N95 filtering facepiece respirators, used in an occupational setting regulated by OSHA must be NIOSH-approved and used in the context of a complete respiratory protection program per the OSHA regulation 29 CFR 1910.134 ( A complete respiratory protection program includes fit testing which indicates that the proper size facepiece is being worn. Additionally, respirators should be used in accordance with the manufacturer’s instructions. Respirators used outside of the manufacturer’s recommendations are not considered to be fully compliant with the terms and conditions of the NIOSH approval, which may be an issue for OSHA regulated workplaces.

    I am looking for location or place to get a Fit test, which I will need for a N95 mask. I am a dental hygienist and live in the Bay Area. I cant not find someone that is certified to the the fit test and need I since I am in the front line and close face contact when I do my job. I have medical concerns that make this a necessary test to know this type of mask will work for me.
    Can anyone direct me to locations and phone numbers that I can call and schedule. I am to go back very sson and need to schedule this first before my return. HELP PLEASE
    San Jose , Santa Clara, Cupertino, Santa Cruz area would be great, I just can not find anyone or location.
    Thank you

    There are companies/organizations that provide training on how to do a fit test such as FitTesters, Inc.,( and Roy McKay (, etc. The AIHA ( may have additional offerings. The listing of these organizations does not represent NIOSH endorsement and NIOSH does not recommend one organization over the other. The ANSI/AIHA/ASSE Z88.10-2010 standard consists of recommendations for qualifications of persons who conduct respirator fit testing.
    OSHA may be able to provide additional assistance as they regulate fit testing. To reach a regional or area OSHA office, you can go to OSHA’s Regional & Area Offices webpage ( or call 1-800-321-OSHA (6742).

    As somebody who is not fully well versed on the subject I find this to be very insightful, particularly the way OSHA handles it.

    Interesting look at the changes in fit over time. If weight gain or loss was controlled for, what percentage changed over the first two years? Also, I have been tryin to find data on fit testing impacting respiratory infections. Does anyone know and studies focused on fit testing and downstream effects?

    Weight analysis of the combined data from visits 2–7 showed that of the subjects who lost 20 lb, 24% had unacceptable fit. However, the percentage changed over the first two years was not estimated when weight gain or loss was controlled for. We are not aware of any study that was focused on fit testing and downstream effects.

    Please OSHA reconsider the TIME FRAME. Yearly fit testing is VERY EXPENSIVE and BURDENSOME especially to nursing schools. And hospitals. Weight gain or loss and the frequency of using an N95 is very minimal and is low priority in the big scheme.
    I am an RN and an educator , fit testing should be every 2-3 years – NOT YEARLY! As an RN we are required to complete CPR every 2 years, but FIT testing every year??!! Doesnt make sense!
    Please OSHA take the burden of this costly low priority requirement and CHANGE to every 2-3 years!!

    Thank you for your comment. NIOSH is the federal institute that conducts research and makes recommendations for preventing work-related injuries, illnesses, and deaths. The 2016 NIOSH study* on which this NIOSH Science Blog is based supports that fit testing be performed annually. Workers rely on an appropriately fitting respirator to achieve the expected level of protection of their type of respirator. Fit testing verifies this. As described in this science blog, the 2016 study found that respirator fit did change over time. The greater the weight loss, the higher the chance that respirator fit will change. The estimated percent of workers whose respirator did not fit them increased with increasing length of time between fit tests, from 10% at Year 1 to 20% at Year 2, doubling those at risk for exposure if not fit tested, and to 26% at Year 3.

    *Zhuang, Bergman, Brochu, et al. (2016). Temporal Changes in Filtering-Facepiece Respirator Fit. Journal of Occupational and Environmental Hygiene. 13(4):269–278.

    Your post offers helpful background and guidance on a vital step in making sure respiratory protection is effective: the fit test. The many fit test techniques, the importance of a good fit, and the function of fit testing in ensuring worker safety have all been explained clearly. It is clear from your writing that you are passionate about improving workplace safety. We appreciate you spreading the word about this post and helping people learn more about the importance of fit testing.

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