Respirator Fit Capability Testing: ASTM Standard F3407-20, ASTM Standard F3407-21 & ASTM Standard F3502-21

RHP Risk Management offers performance testing for Respirators and Face Masks to regulatory standards under ASTM Standard F3407-20, ASTM Standard F3407-21 and ASTM Standard F3502-21. These standards can be used by respiratory device manufacturers to design, develop, and produce better fitting respirators and face masks for general public use.

What are the ASTM Respirator and Face Mask Standards?

To address the need for a fitting characteristic evaluation, the National Institute for Occupational Safety and Health (NIOSH) requested that the American Society for Testing and Materials (ASTM) develop a voluntary consensus standard. In response, the ASTM International developed consensus standards ASTM Standard F3407-20 and ASTM Standard F3502-21. The new ASTM standards are consensus standards developed by a non-federal entity. Unlike federal regulations or statutes, consensus standards are recommendations or practices that do not have a force of law and are created by a non-governmental group of experts.

Testing Requirements for masks ensure that design and performance requirements are met. Filtration efficiency and breathability testing are carried out by RHP’s ISO-17025 accredited laboratory following the methods in Section 8 of the ASTM Standard. The leakage ratio requirement is determined using a modified version of the test procedure described in the ASTM Standard Test Method for Respirator Fit Capability for Negative-Pressure Half-Facepiece Particulate Respirators F3407-20 and F3407-21 and Standard Specification for Barrier Face Coverings F3502-21).

Performance and testing criteria define minimum barrier face covering filtration efficiency and airflow resistance performance properties. Sub-micron particulate filtration efficiency represents the ability to capture and reduce respirable droplets and aerosols that potentially contain viruses and bacteria. Airflow resistance represents the wearer’s ease of breathing or breathability while wearing the barrier face covering. The impact of repeated cleaning or laundering on continued performance is applied for measuring performance properties for those barrier face coverings that are intended to be reusable. Manufacturers are permitted to also provide test results for bacterial filtration efficiency (BFE) as supplemental information to the mandatory performance measurement of sub-micron particulate filtration efficiency.

NIOSH Bivariate Panel

To test the fitting characteristics, RHP Risk Management follows the RFC Standard using 25 human subjects with various lengths and widths of face sizes using the NIOSH Bivariate Panel representing the U.S. civilian workforce. The panel cells are numbered 1 through 10. When the test subject’s face length or face width falls on the cell boundaries, the test subject is classified into the higher number cells, designated by larger facial dimensions.

RHP’s Fit Testing Procedures

Subjects enter a chamber containing a sodium chloride (salt) aerosol and perform eight exercises (normal breathing, deep breathing, turning head side to side, moving head up and down, talking, grimacing, bending over, and normal breathing).

The 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 chamber 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 model to pass the RFC test.

For one-size models, test subjects who do not obtain an overall passing result (that is, a fit factor of at least 100) will repeat the seal check and RFC test procedure after doffing and redonning the same respirator (or a different respirator of the same size and model). If an overall passing result is not obtained after the additional donning, the test subject will be recorded as failing the RFC test. At least 13 of 25 test subjects must obtain an overall fit factor of 100 or greater for the model to pass the RFC test.

For multiple-size models, test subjects who do not obtain an overall passing fit factor result will doff the respirator, don another respirator of the same size, and repeat the test procedure. Subjects who still do not achieve an overall passing result will select another size (from the same respirator model) and repeat the RFC test procedure. Subjects who do not achieve an overall passing fit factor result on any of the facepiece sizes after wearing all the available sizes for that respirator model that will be recorded as failing the RFC test. At least 13 of 25 test subjects must obtain an overall fit factor of 100 or greater for that model. Of the test subjects passing the RFC test, one must be from each of the following groups: Group A consisting of NIOSH bivariate panel cells 1, 2, and 3 with two subjects per cell; Group B consisting of NIOSH panel cell 4 with five subjects, cell 5 with two subjects, cell 6 with two subjects, and cell 7 with four subjects; and Group C consisting of NIOSH bivariate panel cells 8, 9, and 10, with two subjects per cell. The number of subjects in each is based on population distribution of the NIOSH bivariate panel, as explained in a 2007 paper published in the Journal of Occupational and Environmental Hygiene. It is the respirator model and not the individual sizes that pass or fail the RFC test.

The Importance of Performance Validation Testing  – Jacob Persky, MPH, CIH; Wendi Egan; Roy McKay, Ph.D.

ASTM F3407-20 & ASTM F3407-21 Respirator Fit Standards

ASTM’s personal protective clothing and equipment committee (F23) developed the ASTM F3407-20 Standard Test Method for Respirator Fit Capability for Negative-Pressure Half-Facepiece Particulate Respirators (RFC Standard).

The ASTM Standard F3407-20 provides increased assurance to respirator purchasers and users that respirators that meet the requirement of this standard can be expected to effectively fit persons with various length and widths of faces, such as long and narrow or short and wide, when fit tested as part of a complete respiratory protection program in accordance with 29 CFR 1910.134.

The standard provides detailed instructions for performing a respirator fit capability test to determine the fit of air-purifying, half-facepiece respirators, which will include both filtering facepiece respirators and elastomeric respirators equipped with any type of particulate filter. Conformity assessment program scheme owners, such as the National Institute for Occupational Safety and Health (NIOSH), may be able to adopt and use the RFC standard.

ASTM F3502-21 Barrier Face Covering Standard

ASTM International’s committee on personal protective clothing and equipment, along with input from NIOSH, developed the ASTM 3502-21 Standard Specification for Barrier Face Coverings. While barrier face coverings (BFCs) are not respirators or surgical masks, the masks worn to prevent the spread of larger droplets that carry infectious organisms, but do not have to meet federal standards to confirm their performance. The new ASTM International standard is a consensus standard developed by a non-federal entity; this is the first standard to address this category of PPE.

BFCs that meet the ASTM F3502 requirements are designed to be used by the general public to cover both the mouth and nose with two primary functions:

  1. To provide source control by containing the user’s respiratory secretions and “reducing the number of expelled droplets and aerosols from the wearer’s nose and mouth into the air”
  2. To help protect the user by providing “a degree of particulate filtration to reduce the amount of inhaled particulate matter”

NIOSH recommends a new standard in masks, called Workplace Performance and and Workplace Performance Plus masks, for workplaces. Manufacturing masks that comply with the new NIOSH criteria can help protect people in the workplace from SARS-CoV-2, the virus that causes COVID-19. These masks cannot be used as a replacement for respiratory protection when it is needed. The new mask criteria and ASTM Specification for Barrier Face Coverings, F3502-21 (ASTM Standard) determine an expected level of source control performance for workers when wearing the mask according to manufacturer’s instructions.

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, and re-use potential, and leakage.

The current CDC lists barrier face coverings (BFCs) and Workplace Performance/Performance Plus masks that conform to the ASTM F3502-21 standard and NIOSH recommendations.

National Standard of Canada “Performance of Filtering Respirators”: Canadian Standards Association (CSA) CSAZ94.4.1:21

In October 2021, the Canadian Standards Association (CSA) issued CSAAZ94.4.1:21 National Standard of Canada: “Performance of Filtering Respirators”. Citing to the COVID-19 pandemic continuing to drive the need for filtering respirators that meet performance and quality requirements sufficient to protect wearers, CSAZ94.4.1:21 provides guidance for mask designers and manufacturers. Similar to the US standard ASTMF3407-20, but with some slight deviations in , CSAZ94.4.1:21 utilizes a panel of 25 volunteer test subjects with various facial dimensions to make a quantitative determination of adequate respirator fit.  CSAZ94.4.1:21 indicates “Requirements in this Standard may be referenced by government and regulatory agencies for mandatory compliance or for regulatory administration in the development of respirator user guidance.”