Overview of the ASTM F3407 Standard Test Method for Respirator Fit CapabilityPosted on by
The Fundamental Importance of Fit
One of the most important criteria for any filtering facepiece air-purifying respirator to be effective is that a good seal is formed between the respirator’s facepiece and the wearer’s skin. The ability to achieve this seal is called the respirator’s fitting characteristic.
In 1995, when NIOSH put Title 42 Code of Federal Regulations Part 84 (42CFR84) into operation, it did not include an evaluation of the fitting characteristics of respirators approved only for particulates.1 In addition, no voluntary consensus or other government-unique standards existed to evaluate the fit capability of a filtering facepiece respirator prior to it being used in the workplace in an OSHA-regulated fit testing program. Therefore, several studies have been conducted to determine how well NIOSH-approved particulate respirators, especially filtering facepiece respirators, fit wearers.2-8 These studies found a high number of filtering facepiece respirators on the market at the time had poor fitting characteristics. Filtering facepiece respirators that do not fit most employees place an unacceptable burden on respirator program administrators, who must then provide many models and sizes to ensure that every wearer can find a respirator that fits properly.9 In addition, poorly fitting respirators increase the number of fit tests required, increasing costs.10
ASTM International Develops a Voluntary Consensus Standard
To address the need for a fitting characteristic evaluation in the standards, NIOSH requested that ASTM International develop a voluntary consensus standard. ASTM International accepted the challenge, and requested that NIOSH, as leaders in conducting personal protective equipment research for the nation, chair the committee. This approach to standards development is consistent with the National Technology Transfer and Advancement Act of 1995, which directs federal agencies to use consensus standards to address policy objectives and activities where practical.11
ASTM International developed the ASTM F3407 – 20 Standard Test Method for Respirator Fit Capability for Negative-Pressure Half-Facepiece Particulate Respirators (RFC Standard), which was published on October 13, 2020.12 The purpose of the RFC standard is to increase the probability that available respirators fit a general worker population. Respirators meeting this standard will still have to be fit tested in the workplace on each wearer as required by the Occupational Safety and Health Administration (OSHA).13 The RFC Standard does not guarantee that a respirator will fit every wearer.
To test the fitting characteristics, the RFC Standard uses 25 human subjects with various face sizes using the NIOSH Bivariate Panel representing the U.S. civilian workforce.14 The subjects enter a chamber containing a sodium chloride (salt) aerosol and perform eight exercises. Equipment counts the salt particles present in the environment of the chamber and those that leaked into the facepiece. The number of particles that have leaked into the respirator is divided into the number of particles outside the respirator in the chamber to get each subjects RFC Standard results. To pass, a subject must achieve an RFC Standard result of at least 100. An RFC Standard result of 100 means that the number of particles outside the respirator is 100 times greater than inside. At least 13 of 25 (50%) test subjects must obtain an RFC result of 100 or greater for the respirator model to pass the RFC test. The testing procedure is described in more detail in a 2019 Synergist article.15
The RFC Standard is Expected to Have a Significant Impact
The ASTM RFC Standard will enable respirator manufacturers to develop better designed models that fit the worker population. Respirators passing the RFC Standard test method are expected to have better fitting characteristics. The RFC standard will lower costs to respiratory protection programs by reducing the number of different models needed in the program. Purchasers of particulate-only respirators could reference ASTM F3407 in their procurement packages to ensure receiving those with good fitting characteristics. The RFC Standard can be used by organizations, such as NIOSH, to ensure a minimum performance level of for all respirators used within an approval program.16 Both conventional respirator designs as well as novel respirators (such as ones without the prevalent two-strap head harness to provide adequate tension during use and even distribution of pressure) can be evaluated using the RFC standard.19
Ultimately, this RFC Standard defines performance requirements that could be used as part of a conformity assessment program to ensure that NIOSH-approved respirators will fit a specified percentage of the intended user population, thus providing workers with better protection. This is crucial in all industries in which workers are exposed to a variety of agents, one of the most notable examples being the Healthcare and Social Assistance industry sector. Healthcare workers may be exposed to biological agents, e.g., seasonal influenza, Ebola, Severe Acute Respiratory Syndrome (SARS), Influenza A H1N1, and more recently SARS-CoV-2, the virus that causes COVID-19, as well as to chemical agents.17-19
ASTM F3407 can be read for free at https://www.astm.org/COVID-19/ or purchased at https://www.astm.org/search/fullsite-search.html?query=Respirator%20fit%20capability.
How do you think your company or industry could use the RFC standard to improve your respiratory protection program?
Christopher Coffey, PhD, is a former Associate Director for Science for the NIOSH National Personal Protective Technology Laboratory. (retired)
Lisa M Brosseau, ScD, CIH is a respiratory protection consultant and retired professor from the University of Illinois at Chicago (UIC) School of Public Health
Bonnie Rogers, DrPH, RN is a Professor adjunct Department of Environmental Sciences and Engineering, North Carolina Occupational Safety and Health Education and Research Center School of Public Health, University of North Carolina at Chapel Hill.
Jonathan Szalajda, MS, is the Deputy Director of the NIOSH National Personal Protective Technology Laboratory.
- ‘‘Respiratory Protective Devices,’’ Federal Register 60:110 (8 June, 1995). p. 30336.
- Duling MG, Lawrence RB, Slaven JE, Coffey CC. (2007) Simulated Workplace Protection Factors for Half-Facepiece Respiratory Protective Devices. J Occup Environ Hyg 4:420-431.
- Lawrence RB, Duling MG, Calvert CA, Coffey CC. (2006) Comparison of Performance of Three Different Types of Respiratory Protection Devices. J Occup Environ Hyg 3:465-474.
- Coffey CC, Lawrence RB, Campbell DL, Zhuang Z, Calvert CA, Jensen PA. (2004) Fitting Characteristics of Eighteen N95 Filtering-Facepiece Respirators. J Occup Environ Hyg 1:262-371.
- Zhuang Z, Coffey CC, Lawrence RB. (2004). The Effect of Ambient Aerosol Concentration and Exercise on PortaCount™ Quantitative Fit Factors. J Inter Soc Respir Protect 21:11-20.
- Coffey CC, Campbell DL, Zhuang Z (1999). Simulated workplace performance of N95 respirators. Am Ind Hyg Assoc J 60:618-624.
- Reponen T, Lee SA, Grinshpun SA, Johnson E, McKay R. (2011) Effect of fit testing on the protection offered by N95 filtering facepiece respirators against fine particles in a laboratory setting. Annals of Occupational Hygiene. 55(3):264-71,
- NIOSH  NIOSH Investigation of 3M Model 8000 Filtering Facepiece Respirators as Requested by the California Occupational Safety and Health Administration, Division of Occupational Safety and Health. By Berry Ann, R. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Health Hazard Evaluation Report 2010-0044-3109, https://www.cdc.gov/niosh/hhe/reports/pdfs/2010-0044-3109.pdf.
- OSHA Title 29 CFR 1910.134, Appendix A—Fit Testing Procedures. Available at https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. Accessed on November 6, 2020.
- Campbell DL; Coffey CC; Lenhart SW. “Respiratory protection as a function of respirator fitting characteristics and fit-test accuracy, Am Ind Hyg Assoc J 2001 Jan/Feb; 62(1):36-44.
- National Technology and Advancement Act of 1995. Pub, L. No. 104-133. 15 USC 3701 (1996). Available at https://www.govinfo.gov/content/pkg/PLAW-104publ113/pdf/PLAW-104publ113.pdf. Accessed on January 25, 2021.
- ASTM F3407-20 Standard Test Method for Respirator Fit Capab OSHA. Title 29 CFR 1910.134 – Respiratory Protection. Available at https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134. Accessed on November 6, 2020.ility for Negative-Pressure Half-Facepiece Particulate Respirators. Available at https://www.astm.org/Standards/F3407.htm. Accessed on November 8, 2020.
- OSHA. Title 29 CFR 1910.134 – Respiratory Protection. Available at https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134. Accessed on November 6, 2020.
- Zhuang, B. Bradtmiller and R.E. Shaffer (2007). New Respirator Fit Test Panels Representing the Current U.S. Civilian Work Force, Journal of Occupational and Environmental Hygiene, 4:9, 647-659.
- Coffey C; Miller C. The respirator fit capability test: enhancing the efficacy of filtering facepiece respirators. Synergist 2019 Sep; 2019(9): Digital Extra. https://synergist.aiha.org/201909-respirator-fit-capability-test.
- NIOSH . National framework for personal protective equipment conformity assessment – infrastructure. By D’Alessandro M. Pittsburgh, PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2018–102.
- National Institute for Occupational Health and Safety NIOSH], Workplace Health and Safety Topics: Healthcare Available at https://www.cdc.gov/niosh/topics/healthcare/.
- BLS (Bureau of Labor Statistics) (2018). Career guide to industries: Health care. http://www.bls.gov/oco/cg/cgs035.htm).
- Occupational Safety and Health Administration [OSHA], 2015; Occupational Safety and Health Administration, National Institute for Occupational Safety and Health (2015). Hospital respiratory protection toolkit, Publication # 2015-117.
9 comments on “Overview of the ASTM F3407 Standard Test Method for Respirator Fit Capability”
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if this will increase the availability of OSHA-compliant half face respirator masks capable of being used in pt-facing healthcare situations, specifically in COVID or other virus-based illnesses to be used as protective PPE for the worker, it will be extremely welcome. Picking one’s way thru the myriad of masks to meet the needed healthcare situation is slow and tedious at best, especially in the face of a novel virus. Anything that can improve that process as well is beneficial.
Using ASTM F3407 Standard Method for Respirator Fit Capability will help weed out poorly designed respirators. However, the next step is for respirator manufacturers to implement this voluntary guideline. The best way to achieve the ultimate goal of better fitting respirators is incorporate this guideline or similar guideline, into the requirement for NIOSH approval. Doing so will help ensure that NIOSH-approved respirators have a greater probability of fitting a worker population. This will then be confirmed on an individual basis by having the subject pass an OSHA accepted fit test.
Roy T. McKay, Ph.D.
University of Cincinnati
Excellent information, thank you.
TSI Incorporated has been fielding numerous inquiries regarding ASTM F3407 Fit Capability Standard in the last month (mid-February – mid-March 2021). Inquiries have been coming in from North America, Europe, Asia and Australia. These inquiries from companies and researchers developing and testing Barrier Face Coverings (BFC) to the ASTM F3502 Barrier Face Covering Standard which, references using the ASTM 3407 Respirator Fit Capability quantitative fit testing procedure to get the ASTM BFC Standard “Total Inward Leakage Ratio” measurement in N99 Mode of operation for a Condensation Nuclei Counting based fit test instrument. To that end ASTM F3407 is being used by others than Respirator Manufacturers whom are not as familiar with quantitative fit testing using Condensation Nuclei Counter (CNC) based fit testing instruments. These inquiries from companies and researchers are focused on three sections in ASTM F3407 and they are as follows:
1) Section 7.1 which reads:
7.1 Condensation nuclei counter with particle classifier
technology (for example, a differential mobility analyzer). The
particle classifier technology shall only allow nominal 55 nm
particles to pass through to the condensation nuclei counter for
counting while eliminating the zero-charge and positive-charge
particles from the sample.
The companies and researchers are asking if the “nominal 55 nm particles” are only the negatively charged particles based on the information documented in NIOSH and TSI Studies on using a “differential mobility analyzer” for testing respirators with less than 99% efficient filters. The answer to this is “yes” from these studies that is it indeed “nominal 55 nm negatively charged particles” and appears to be an omission in this standard.
2) Section 7.4.4 which reads:
7.4.4 Aerosol Concentration—The aerosol concentration
shall be well mixed (that is, uniformly distributed) throughout
the chamber (+/-10 %) where the test subject(s) will be performing the test. The concentration shall be stable (that is,+/-10 % of the initial concentration of between 2000 and 8000 particles/cm3) for the duration of the test.
The companies and researchers are asking why both N99 Mode and N95 Mode of operation for a CNC based fit tester equipped with a differential mobility analyzer are not specified in this section? This appears to be an omission of N95 Mode testing criteria in this standard as it is meant to provide the ability to test filtering facepiece respirators with less than 99% filter efficiency (i.e., NIOSH Series 95 Respirators and CE FFP1 and FFP2 Respirator designs). The N95 Mode of operation would have a aerosol concentration between 200 and 800 particles/cm3, when testing respirator designs with less than 99% filter efficiency. If left in the current concentration range of 2000 to 8000 particles/cm3, you would never be able to consistently generate enough nominal 55 nm negatively charged particles (see Section 7.1 discussion), to meet the current aerosol concentration range documented in this section.
3) Section 220.127.116.11 which reads:
18.104.22.168 The test subject shall enter the chamber. The
concentration of particles in the chamber shall be measured
prior to the subject entering the chamber to ensure that it is
between 2000 and 8000 particles/cm3. The concentration of
particles in the chamber shall remain within +/-10 % of the
concentration measured at the beginning of the test for the
duration of the test.
Again, the companies and researchers are asking why both N99 Mode and N95 Mode of operation for a CNC based fit tester equipped with a differential mobility analyzer are not specified in this section as well? This appears to be an omission of N95 Mode testing criteria in this section of the standard as it is meant to provide the ability to test filtering facepiece respirators with less than 99% filter efficiency (i.e., NIOSH Series 95 Respirators and CE FFP1 and FFP2 Respirator designs). The N95 Mode of operation would have a aerosol concentration between 200 and 800 particles/cm3, when testing respirator designs with less than 99% filter efficiency. If left in the current concentration range of 2000 to 8000 particles/cm3, you would never be able to consistently generate enough nominal 55 nm negatively charged particles (see Section 7.1 discussion), to meet the current aerosol concentration range documented in this section.
With all this being identified, I formally recommend review by the ASTM F3407 Fit Capability Standard Committee, to discuss making these appropriate updates to this standard to support those companies and researchers that are currently using and will be using this standard moving forward in conjunction with the ASTM F3502 Barrier Face Covering Standard.
Greg Olson, M.S.
Global Product Specialist – Industrial Hygiene & Respiratory Protection
TSI Incorporated USA
Greg is correct.
I was a member of the ANSI Z88.15 committee, the predecessor of ASTM F3407. In the last ANSI draft, the following sentence was written:
3. Conducting the Respirator Fit Capability Test
3.1. Check the respirator to make sure the sampling probe and line are properly attached to the facepiece and that the TSI PortaCount®Pro+ Fit Tester 8038 is in the N95 Companion mode for series 95% efficiency filters per manufacturer’s instruction. For series 100% and series 99% efficiency filters, the N95 Companion mode is not used.
This was removed by ASTM, for reasons that are unclear to me.
Roy McKay, Ph.D.
Thank you for your comment.
Thank you for posting this informative blog. keep sharing
The contradiction Greg describes is concerning, but I think that it need not concern F3502 mask manufacturers, because no matter what Portacount Mode(s) F3407 describes, the ASTM F3502 standard instructs laboratories to modify the F3407 method so that barrier face coverings are tested only in N99 Mode or equivalent— i.e., without engaging a particle classifier.
Here are the relevant modifications to the F3407 method which are stipulated in sec. 8.3 of ASTM F3502 and in that section’s footnote:
— “If a condensation nuclei counter is used, testing shall be done with a condensation nuclei counter operating in the N99 mode only”;
— “If a condensation nuclei counter is used and equipped with a classifier, the N95 mode shall not be used for testing”;
— “For example, the N95-Companion Technology would not be used with the TSI PortaCount Models 8038 or 8048.”
Why would ASTM F3502 prohibit use of N95 Mode? For clues we might consider the current list of approved F3502 devices. It includes many masks with only 20% to 30% FE at 85 LPM and ~0.3 microns. See: https://wwwn.cdc.gov/PPEInfo/RG/FaceCoverings
No such mask can be expected to capture negatively charged nanoparticles nearly as efficiently as the certified respirators used to validate N95 Mode. So testing F3502 masks in N95 Mode could confound peripheral leakage with some unknown high percentage of filter penetration by nanoparticles. Instead measuring only total inward leakage for all masks (or, to be more precise, measuring fit factor with N99 Mode—the reciprocal of TIL) avoids that particular problem.
Ari Solomon, Ph.D.
Thank you for your comments. The ASTM technical committees responsible for these standards will be advised of your comments and address them as appropriate for future editions of the standards.
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