Overview of The ASTM F3502-21 Barrier Face Covering Standard

Posted on by Jonathan Szalajda, MS; Jeffrey O. Stull, MS; and Lisa M. Brosseau, ScD, CIH


Unlike respirators and surgical masks, the masks worn to help prevent the spread of COVID-19 don’t have to meet federal standards to confirm their performance. That lack of standardized testing and labeling has left mask users with no way to compare face covering products to make informed decisions when choosing a face covering.

While barrier face coverings (BFCs) are not respirators or surgical masks, they may prevent the wearer from spreading larger droplets that can carry infectious organisms, such as the virus that causes COVID-19. ASTM International, with input from NIOSH, recently developed a new Barrier Face Covering standard (number F3502-21) to establish a set of uniform testing methods and performance criteria. To meet the ASTM standard, a BFC must meet certain design and performance requirements, including filtration efficiency and air flow, which must be tested by an accredited laboratory and labeled accordingly.

The new ASTM International standard is a consensus standard developed by a non-federal entity. Unlike federal regulations or statutes, consensus standards are recommendations or practices that do not have the force of law and are created by a non-governmental group of experts.

The classification system in the ASTM barrier face covering standard was not intended to define the actual overall performance of the barrier face covering as either a means of source control or personal protection. Rather, the development of this national standard provides a consistent baseline that allows comparison of product claims in terms of filtration efficiency, breathability, re-use potential, and leakage.

Filtration efficiency – The level of filtration efficiency refers to how well the BFC material blocks particles from going through it when the user is exhaling or inhaling. The higher the level of filtration efficiency, the more particles are blocked from penetrating through the material. Barrier face coverings may be rated at two levels of filter efficiency, 20% or 50%, (and must be labeled accordingly) when evaluated with methods similar to those used by NIOSH to evaluate respirator particulate filters. Face coverings with 20% or higher filtration have lower performance than those with 50% or higher filtration. A NIOSH-approved respirator will perform at a higher rated efficiency than a BFC tested to the ASTM standard. For example, a NIOSH-approved respirator with an N95 filter has a minimum filtration efficiency of 95% for the test aerosol at the test flow rate of 85 liters per minute.

Breathability – If a barrier face covering is hard to breathe through, users will not be able to wear it for long periods. Therefore, ASTM incorporated requirements for breathing resistance into the specification, requiring a method similar to that used to evaluate respirator filters. The airflow resistance of a BFC must be 15 mm H2O or below. This value was selected because it represents a level thought to be acceptable to most users and is similar to the resistance for many N95 filtering facepiece respirators. The standard also recommends a second performance level of 5 mm H20 or below, which indicates better performance and a more comfortable BFC.

Re-use potential – Products marketed as “reusable” must meet the ASTM standard requirements for filtration efficiency and breathability when right out of the package and after the maximum number of laundering or cleaning cycles identified by the manufacturer.

Leakage– Leakage represents how well the barrier face covering prevents particles entering or exiting the BFC around the edges when worn on the face. The manufacturer must specify how, through their design and manufacturing process, they minimized leakage. The standard also describes a non-mandatory quantitative method for evaluating leakage using a group of human subjects.

Additionally, the standard provides design requirements for the general construction of masks, use of nonirritating and nontoxic materials, flammability, sizing, and shelf life. Manufacturers can now report that their barrier face coverings meet the baseline performance measures described in the standard. The label includes information about filtration efficiency and breathability. Users and purchasers can now select ASTM-compliant barrier face coverings based on their labeled performance in filtration, breathing resistance, and leakage.

Additional resources about the ASTM barrier face covering F3502-21 standard are available at https://astmppecollaboration.org/. ASTM International is currently providing no cost public access to their COVID-19 related standards.

Barrier face coverings are not respirators or surgical masks and are not regulated by NIOSH, or approved by NIOSH pursuant to the respirator approval program.  The NIOSH respirator approval program certifies that an individual or combination of respirators has met the minimum requirements of federal regulations at 42 C.F.R. Part 84, and that the manufacturer is authorized to use and attach a NIOSH approval label.  More information on this program is available here.

As of August 10, 2021, a list of ASTM F3502 compliant products is available. The list will be updated as new masks are evaluated.

Jonathan Szalajda, MS, is the Deputy Director of the NIOSH National Personal Protective Technology Laboratory.

Jeffrey O. Stull, MS, President of International Personnel Protection, Inc., which provides independent expertise on PPE and standards development.

Lisa M. Brosseau, ScD, CIH is a Research Consultant with the University of Minnesota Center for Infectious Disease Research and Policy and retired professor from the University of Illinois at Chicago (UIC) School of Public Health.


Posted on by Jonathan Szalajda, MS; Jeffrey O. Stull, MS; and Lisa M. Brosseau, ScD, CIH

36 comments on “Overview of The ASTM F3502-21 Barrier Face Covering Standard”

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 ».

    Thanks for this overview of this new standard. Hopefully, it will be effective at improving face covers for the public. As these face coverings are not respirators, they should not be used to replace FFRs or other respirators, correct? Given the experience over this last year with this pandemic, it seems that many more employers should be providing workers with FFRs to protect against aerosol transmission of the coronavirus.

    You are correct, face coverings are not respirators and should not be used in situations where respiratory protection is needed.

    Grateful for this explanation about the ASTM standard. And for Mark Catlin’s comment about the need for real respirators to protect workers who can’t or aren’t allowed to stay at home, given the airborne transmission of this virus.

    Where is any objective evidence re source control/protection?


    NOTE 1: “The source control/protection provided by barrier face coverings depends on
    several factors not considered in this specification, such as
    material degradation from wearer challenges including
    length of time the barrier face covering is worn.”

    NOTE 2: “Nothing in this standard addresses or implies a quantitative assessment of
    outward leakage and
    no claims can be made about the degree to which a barrier face covering
    reduces emission of human-generated particles.”

    Thank you for the comment. The notes that you are referring to are from the F3502-21 standard. Users of the F3502-2 1standard should refer to Section 1 (Scope) and Section 4 (Significance and Use), of that document to understand the specific areas addressed by the standard and its limitations, along with the reasons for choice of specific requirements.

    Good to see the CDC recognize the work that went into the F3502 standard. I’m hopeful this standard will be referenced in the next update to the CDC’s formal mask guidance and/or in OSHA’s Temporary Emergency Standard (ETS).

    The filtration efficiency and breathability reporting required by the ASTM F3502 standard should be a standard part of universal source control as we work to get this pandemic under control, especially as the vaccine-skeptical population begins returning to offices.

    On what basis, a person shall select and buy a Barrier Face Covering. Is there , at least, a crude/simple method?

    You are Right, Face coverings are not respirators and should not be used in situations where respiratory protection is needed.

    Thank You!


    Does the ASTM Level 3 Certification of masks meet or exceed the ASTM 3502-21 Mask certification standards.

    I am a layman, so if possible, please use layman’s terms to describe the comparative characteristics.

    Thank you
    J. White

    The short answer is no.

    We believe that the Level 3 certification you are indicating is actually applied to medical face masks or surgical masks that are covered by a different ASTM standard — ASTM F2100. That standard has some of the same test properties as addressed for the Barrier Face Covering in ASTM F3502, but uses different test methods. The two standards are not directly aligned, so it is not possible to do a 1-to-1 comparison. For example, Level 3 requires a fluid resistance test, which is not part of ASTM F3502. On the other side, a medical face mask that passed Level 3 would need to be tested against the specific requirements in Barrier Face Covering standard ASTM F3502 testing by an accredited laboratory and specific labeling for the product and package, which is different from that of a Level 3 medical face masks. Therefore, a unit passing one test would not guarantee that it would pass the other.

    Please please give me some actionable advice that I can implement TODAY! CDC website says to “Look for masks that are labeled as MEETS ASTM F3502.” Tell me exactly which ones meet that standard today!

    Thank you for this much needed standard. We feel a new standard was needed as there is much public confusion of the different levels and types of certifications.

    I agree with Jack. While I’m happy this standard was made, I can’t find an, “ASTM F3502” mask from a reputable retailer. Practical instructions on how someone could make their own mask would be much more helpful right now. Knowing which materials to use for the layers and some sewing patterns would be extremely helpful! In the beginning of this, the Surgeon General even had a YouTube video (although it was not well advertised 🙁 ) on how to easily make a multilayered bandana mask from a bandana & rubber bands. It was super helpful, economical, & practical for the lay public. We need more of something like that. Pleeease.

    Reply: CDC has a guide to masks Your Guide to Masks as well as the Types of Masks and Respirators on its website. Wearing a mask is one of the most important ways to reduce the risk of getting and spreading COVID-19. Improve the Fit and Filtration of Your Mask to Reduce the Spread of COVID-19 describes the types of masks available and strategies that can be used to better protect the wearer and the people they interact with. Wearing any type of mask correctly is better than not wearing a mask at all.

    masks: We have vaccine and now we need to the whole package: reliable well made masks made in US. at a reasonable priced.

    I keep getting (questionable) info on how an N95 mask MUST be constructed and the materials used. Is there a NIOSH, ASTM, CDC, FDA, etc. deign and construction standard or are the requirements simply a test standard that a product, however constructed, and using whatever materials can pass?

    And please do publish my email address – I would like comments directed back to me.

    No, there is no particular design or material of construction required for N95 respirators. There are literally hundreds of different designs approved by NIOSH for N95 masks. To receive NIOSH approval they must meet the performance requirements identified in eCFR :: 42 CFR Part 84 — Approval of Respiratory Protective Devices. Additionally, the manufacturer must have quality control procedures and manufacturing facilities to assure NIOSH that they have the ability to reliably and continuously manufacture approved respirators that meet the standard.

    Additional information about the NIOSH Respirator Approval Process in Respirator Approval Information

    In Europe we have two different standards. One for Surgical Mask tested against droplets, to measure bacterial filtration and one other for Filtering Masks (respirators) tested against droplets and aerosols, designed for virus filtration. High concentration of virus in aerosols will penetrate the Surgical Masks easily. Filtering Masks (respirators) in accordance to the European standard EN149 require 94 % filter efficiency and maximum 11 % leakage (mask filter Class FFP2). Filtering Masks (respirators) in the highest Filter Class FFP3 require 99 % filter efficiency and maximum 5 % leakage.

    I have and use the masks that adhere to F2100-19. These are 3 ply disposable masks and can be adjusted to fit a child’s face. Now I see the standard F3502 as recommended by CDC. I am also reading that both these standards cannot be compared head to head. As a trained and educated engineer, I am confused. It does not appear that I need to throw away my F2100-19 masks and buy new ones. How does one compare like for like? thanks

    The masks you purchased masks are designed and tested for use as medical or surgical masks. They were tested against a specific ASTM standard — ASTM F2100-19. That standard has some of the same test properties as addressed for the new Barrier Face Covering standard, ASTM F3502, but uses different test methods. For example, ASTM F2100-19 requires a fluid resistance test (since medial masks are designed to protect the wearer from splatter from bodily fluids during medical procedures), which is not part of ASTM F3502. On the other hand, a medical face mask that passed F2100-19 tests would not necessarily meet the specific requirements in Barrier Face Covering standard ASTM F3502 which requires testing by an accredited laboratory and specific labeling requirements for the product and package. The two standards are not directly aligned, so it is not possible to do a 1-to-1 comparison. Wearing either type of mask will provide protections over not wearing a mask at all. We don’t think it is necessary to throw away your F2100-19 masks, but you may want to consider which type to procure for the future based on your intended use. See Your Guide to Masks for guidance.

    I’m amazed that this thread basically died back in October, even after the emergence of Omicron. I had some hope that the ASTM standard was the beginning of a more intelligent approach to performance testing, reusable masks and industry standards. Alas…

    Nevertheless, note on the link to the ASTM tested masks: https://wwwn.cdc.gov/PPEInfo/RG/FaceCoverings, two reusable manufacturers seem to stand out in both filtration effectiveness and breatheability. Would be that leakage tests were also a mandatory part of the standard….

    Masks made to the ASTM standard cannot be used as a replacement for respiratory protection when respiratory protection is needed. We agree that a quantitative leakage assessment is an important performance criteria for masks. At this time, the ASTM standard performance criteria addresses filtration and breathability, quantitative leakage assessment is an optional requirement. NIOSH recommends quantitative leakage assessment and labeling criteria in masks, called Workplace Performance and Workplace Performance Plus masks, for use in workplaces Making Masks for the Workplace (cdc.gov).

    I would concur with L. Binner. It is disappointing to not see more momentum and mentions of this BFC standard given that we are still very much in the midst of a pandemic and more efficient masks are still needed (vs. cloth masks).
    Is there a particular reason the CDC or States Health Departments are not more pro-actively recommending the use of masks meeting the ASTM F3502 standard? Here in Utah for instance, they (Salt Lake County Health Dept.) are recommending KN95’s or respirators over cloth masks, nothing in between.
    Additionally, is there a plan to increase the level of efficiency of this standard? “N20” performance seem rather low.

    Thank you for your comments. The BFC is intended to be used in conjunction with public health recommendations regarding protective measures worn by the public. The ASTM F3502 specification provides a standardized set of performance requirements that includes rigorous test methods for particulate filtration efficiency and airflow resistance. By providing a specification of how testing is supposed to be performed along with criteria for reporting that information as well as labeling of the product itself, it is possible for specifiers and other organizations to dictate higher levels of performance. The two levels of performance were achieved through the ASTM consensus process for the first edition of the standard. As more information is obtained about these products and the measurement of their performance, future revisions of the specification will be carried out by the ASTM task group.

    I believe F3502 was created at a time when exposure was considered primarily to come from large droplets and formites so airborne particulate transmission was not considered as relevant, hence lower filtration bar. Now the science proves otherwise it’s high time for a review of the requirements for a barrier mask, in reality we need a US standard for Civilian Daily Use Respirator that replaces China’s ear loop KN95 and still provides a high level of fit, filtration and breathability. My vote would be for FN95 or similar, more memorable than F3502-21 to gain adoption.

    Thank you for your comments. CDC updates its consumer webpage describing the types of masks and respirators used to prevent the transmission of SARS-CoV-2. Masking is a critical public health tool to prevent the spread of COVID-19, and it is important to remember that any mask is better than no mask. To protect yourself and others from COVID-19, CDC continues to recommend that you wear the most protective mask you can that fits well and that you will wear consistently.

    “Barrier face coverings may be rated at two levels of filter efficiency, 20% or 50%, (and must be labeled accordingly)…”. 20% or 50% of what size particle? We are led to believe that all of these masks protect against covid, but there are disclaimers on the shipping containers that say they do not offer protection for covid. If the size of the covid particle is smaller than the filtration capability of the mask, then what good are they regardless of proper use and fit? 50% of .1 micron particles is better than 50% of 1 micron. If the it’s 50% of 1 micron then it’s 0% of a .1 micron particle. What is the specification?

    No specific claims are made for protection against COVID-19 as part of the ASTM F3502 specification. The submicron particulate filtration levels are determined using a very rigorous test for measuring the effectiveness of the face covering materials. The particulate filtration testing used in the ASTM F3502 standard is based on the same method applied to N95 respirators, testing with a relatively small particle size, particles with a mass median aerodynamic diameter of 0.3 microns.

    Is this ASTM F3502-21 standard comparable to China’s KN95 and Korea’s KF94 standards?

    If not, is there any comparable standard certified here in the USA?

    If I understand correctly, N95 respirators are the gold standard, but N95s have to have headstraps.

    But the earloop style seems to be the most used and preferred by the general public.

    It would be so helpful have a familiar USA standard other than N95, that we could look for when purchasing a protective mask. It’s confusing to have to look for standards used by other countries (KN95 or KF94).

Post a Comment

Leave a Reply to K. N. Krishna Prasad Cancel Reply

Your email address will not be published. Required fields are marked *

All comments posted become a part of the public domain, and users are responsible for their comments. This is a moderated site and your comments will be reviewed before they are posted. Read more about our comment policy »

Page last reviewed: August 11, 2021
Page last updated: August 11, 2021