Respirator Fit Comparison Study Shows that Many Popular N95 Disposable Respirators Do Not Meet Fit Capability Standard

Without proper fit and seal against your face, an N95 may leak around the edges and offer far less protection than it claims

West Bridgewater, MA (September 15, 2022) – A recent comparison study of some of the most popular commercial N95 disposable respirators shows many of those N95s struggle to seal well against the wearer’s face and therefore may not protect as well as they claim. The study was conducted using the relatively new ASTM F3407-20 Respirator Fit Capability (RFC) Standard to evaluate respirator product designs on overall fit capabilities.

The study pointed out the dangers of wearing a disposable N95 respirator without ensuring that it fits and seals well around your face. 75% of the N95s tested did not meet the fit capability standard. As a result, they did not provide the 95% filtration protection they were designed for.

Global advanced materials manufacturer Shawmut Corporation recently presented the comparison study of popular commercial N95 filtering facepiece respirators at the 2022 International Society for Respiratory Protection Conference (ISRP2022). Held once every two years, the ISRP conference serves as a global forum for the exchange of knowledge related to the science, technology, regulation, development, and practice of respiratory protection.

The purpose of Shawmut’s comparison study was multi-fold, with an emphasis on assessing the ability of the ASTM F3407 Respirator Fit Capability (RFC) Standard to compare the fit capability performance of a range of several popular commercial NIOSH-approved disposable N95 filtering facepiece respirators (FFRs) of various designs – molded cup, flat-fold, trifold and duckbill. A focus was also placed on understanding how FFR design and construction factors may impact overall fit performance, as well as assessing the relative performance of other popular FFR designs in the market at the time of the study (such as KN95s) compared to N95 FFR designs.

“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 for a wider range of face sizes,” said James Wyner, CEO of Shawmut. “Achieving high filtration is relatively easy; achieving a good seal in a mask that has high filtration is a challenge,” Wyner added. “That’s why evaluating how well a respirator fits a wide range of people, in accordance with the ASTM F3407 standard, is so valuable.”

Several years prior to the start of the pandemic, NIOSH identified that a standard was needed to evaluate the fit capability of an FFR prior to its inclusion in an OSHA-regulated workplace fit testing program, as that was not a part of its N95 regulatory process. NIOSH requested ASTM International develop such a standard. Working with NIOSH, ASTM developed the F3407 RFC Standard and published it in October of 2020. Per NIOSH, the purpose of the RFC standard is to increase the probability that available respirators fit a general worker population. NIOSH is currently reviewing how to incorporate the ASTM F3407 RFC Standard into its regulatory process. The RFC Standard is currently voluntary for respirator manufacturers.

Shawmut’s comparison study included 450 individual subject tests and 3,600 interior air samples of 18 popular and readily available disposable respirator market models using a 25-person test group. The respirator model lineup comprised 12 N95s, 5 KN95s and 1 KF94.The test group included 13 males and 12 females and selected in accordance with the NIOSH bivariate test panel, which is designed to be representative of the U.S. civilian workforce.

Overall, there were large differences between N95 designs tested in terms of fit capability and minimum levels of protection. 75% (9 of the 12) of the N95s tested did not meet the fit capability standard (which calls for a minimum fit capability of 50% of the 25 panelists), and fit performance varied dramatically across individual N95 models. The study found that there is a great deal of variability in the fit of different respirator models across the human test group. Some models performed consistently across subjects, while others performed inconsistently or poorly on most subjects. Of the 12 N95 models tested, only 3 passed the RFC standard. Two others fell 1 panel subject short of passing. Six of the 12 tested did not even achieve a 25% passing score (see attached chart).

Fit variability may be an important metric for general consumer use with some respirators offering a more consistent fit across wearers than others. With regard to form factors, some styles seemed to be more robust than others, with cup designs performing better than duckbills and flat-folds. However, within each style there was still a great deal of variability in performance across subjects. The results suggest that fit variability is an important consideration for consumers who will be selecting an FFR. There appears to be an advantage to choosing a style that performs well on individual test subjects as opposed to one that fits poorly on everyone; however, there are no guarantees that a given style will perform consistently over time or across different individuals.

No KN95 mask passed a fit test on any individual in the comparison study panel. This indicates that KN95 masks do not perform well even with high-quality 95% filtration. Wyner added, “The idea that a properly vetted KN95 is any way comparable to an N95 is categorically wrong and dangerous, and KN95 masks do not deliver comparable safety performance. The KN95s tested may pose risks to the general public and should not be conflated with N95s.”

The Importance of Respirator Fit and Seal

Since their development in the 1970s, NIOSH-approved N95 filtering facepiece respirators have been at the forefront of respiratory protection. However, in recent years, there has been debate regarding the dynamic fit characteristics of these respirators and there appear to be large differences between N95 designs in terms of fit capability and minimum levels of protection.

Until recently, public health organizations have not had a tool to identify which NIOSH certified filtering facepiece respirators adequately protect workers in the workplace. Product development efforts have lagged, creating worker protection gaps, and users are hard pressed to know if an FFR will fit their face or protect them from harmful gases, vapors and/or particles while they are working. The ASTM F3407 standard represents a significant step forward in respiratory protection and will make it much easier to select appropriate respiratory protection based on face fit capabilities. It is expected that as knowledge of respirator fit increases among users, increased use will also lead to increased demand for better-designed respirators that fit and seal to the wearers specific face shape and size.

Ultimately, if a respirator does not fit you and seal properly, it cannot protect you, no matter how comfortable it is, what fancy features it has or how much marketing muscle is behind it. The ASTM F3407 Standard was found to be essential to understanding respirator fit performance and adoption of the standard is likely to produce improvements in respirator design effectiveness.


About Shawmut Corporation  

Shawmut Corp. uses materials innovation to improve people’s lives, employing expertise in fabric formation, coating, and laminating to deliver high-performance materials and components to the Automotive, Health & Safety, Defense, Protective, and Custom Laminating Solutions verticals. Shawmut applies its keen understanding of the unique challenges of materials for medical applications to its Protex™ line of personal protective equipment (PPE), including high-quality N95 respirators and non-surgical isolation gowns, all manufactured in the U.S. To learn more about Shawmut’s N95 respirator, click here. As a fourth-generation, family-run global company headquartered in West Bridgewater, MA, Shawmut employs over 700 employees worldwide in multiple manufacturing plants and commercial offices across North America, Europe, and Asia.  Shawmut can be found online on LinkedIn, Facebook, and Instagram. To learn more, visit

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