Overview of The ASTM F3502-21 Barrier Face Covering Standard

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.