Does My Face Covering Work? Ask ASTM F3502
Each industry has its own unique hazards, making the search for a face covering difficult.
- By Hugh Hoagland, Michael McDonald, Ruwan Wijesundera, Rob Taylor, Brian Shiels
- Aug 02, 2021
The coronavirus made popular the face coverings in public spaces all over the world as a means to stop transmission of the virus. This means that face masks, or cloth face coverings (CFCs) were also commonly found in workplaces of all kinds.
ASTM's new F3502 Barrier Face Covering Specification, issued February 15, 2021, comes in time to improve the fit, function and other characteristics of face masks. This standard was issued unusually fast in ASTM consensus and addresses everything you need to know about how to test cloth/barrier face coverings.
ASTM F3502 points to several test methods or specifications to assist test labs, certification bodies, manufacturers and end users to assess and properly market CFCs for worker protection when additional respiratory protection is not needed in the work environment. These include, but are not limited to, filtration, breathability and fit or leakage assessments. Let’s take a look at each one.
Filtration. The ASTM F3502 standard addresses filtration by testing 20 samples of cloth face coverings—ten in new condition and ten after a maximum number of cleaning cycles (as specified by manufacturer). These face coverings are tested for both sub-micron particulate filtration efficiency (PFE) and airflow resistance using a method similar to N95 respirator testing with modified acceptance criteria. Testing is performed on full products or, for certain products, the area of the product that fully covers the person’s nose and mouth.
Since CFCs are normally made of launderable fabrics, the standard also requires the testing of PFE’s impact from routine laundering or cleaning. This is most commonly accomplished by normal machine laundering to a standard test method like AATCC TM 135 (North American home laundry). But other laundry preconditioning methods are available, including ISO 6330 (European home laundry), NFPA 2112 (industrial laundry) or hand washing.
Breathability. Airflow resistance is tested by a method described in the standard but is similar to inhalation/exhalation resistance testing for N-series respirators: Method for Determination of Inhalation and Exhalation Resistance for Air-Purifying Respirators as per NIOSH Procedures TEB-APR-STP-0003 AND TEB-APR-STP-0007.
ASTM F3502 again uses a two-level classification system for airflow resistance/breathability, with Level 1 (good performance) for cloth face coverings with airflow resistance being between 5 mmH2O to 15 mmH2O, and Level 2 (better performance) having airflow resistance less than 5 mmH2O. Any cloth face covering with resistance higher than 15 mmH2O would be non-compliant with ASTM F3502.
Fit or Leakage Assessment.
The F3502 Specification requires the manufacturer to self-report a leakage assessment that can be as simple as a product design analysis. For manufacturers wishing to provide a quantitative analysis, they can supplement (but not replace) that leakage assessment with F3407 Test Method for Respirator Fit Capability for Negative-Pressure Half-Face piece Particulate Respirators to determine the leakage ratio.
Other acceptable “examples of means to accomplish a leakage assessment could include dimensional analysis, computer modeling, placement of barrier face coverings on standardized head or head/torso forms and judging their respective areas of coverage and conformity to the head or head-torso form face showing conformance to the fit and sizing characterizations of AATCC M14-2020 or performing a quantitative analysis.”
Other fit tests are required in NIOSH 42 CFR Part 84 (depending on the device) but these tests are stricter than the ASTM F3502 standard.
Four Function Classifications
Based on the above-noted performance levels for PFE and airflow resistance, there are four possibilities for overall performance. These are based on the lowest efficiency and highest resistance measured for the 20 tested samples (inclusive of samples subjected to cleaning/laundering):
- Level 1 for both PFE and Airflow Resistance
- Level 1 for PFE and Level 2 for Airflow Resistance
- Level 2 for PFE and Level 1 for Airflow Resistance
- Level 2 for both PFE and Airflow Resistance
It should be understood that Level 2 for both parameters represent the best performance of the cloth face covering but fit is also an important consideration. It should also be noted that some individuals with specific medical conditions (adults or children) could perceive difficulty breathing while wearing a barrier face covering with Level 2 airflow resistance.
Flame Resistance vs. Flame Spread
Flame spread and flame resistance are important in some work settings, so ASTM F3502 addresses them by pointing to applicable standards. Standards ASTM F1506 and NFPA 2112 addressed providing some level of protection and assured flame resistance to the CFCs. Neither standard addressed function from a particulate filtration, airflow resistance or fit perspective. Now ASTM guides flame resistance (by pointing to proper standards) and addresses the proper function. (For Fire Fighting see NFPA 1971 and our article on the true arc flash and flame protection afforded by SCBA devices.)
Flame spread is tested on all clothing sold in the U.S. by regulation 16 CFR Part 1610, however, this standard does not address flame resistance as often assumed. Garments can burn in this test method and most do, it is a control of "how fast" they burn. It prevents the sale of Class 3 garments (those who burn too quickly). Cloth face coverings are considered wearing apparel and are subject to 16 CFR Part 1610 at a minimum, and the application to F3502 is that the material flammability/flame spread be Class 1, but for true AR/FR/FFR or other flame rated standards, the CFCs must meet other, more stringent, standards below.
ASTM F1506 for arc rated clothing and the NFPA 2112 for flash fire rated clothing committees moved very quickly to add CFCs to their scope and tone down labeling requirements and certification requirements to help workers exposed to flash fire and arc flash get the PPE they needed early in the crisis but neither of these standards addressed the fit of the CFC, function of breathability or particulate filtration. ASTM F3502 does just that.
- NFPA 2112-2018 issued their changes in August 11, 2020 in TIA 18-1, Reference: various sections in Chapter 1, 2, 3, 4, 5, 6, 7, 8, Annex A and C. This was a change in labeling requirements and third-party certification. The CFCs were not defined as a product so only the components required certification to speed production.
- ASTM F1506-20a updated the standard in Nov. 3, 2020 to include CFC's. with only a change in labeling requirements.
Reuse must be specified by the manufacturer and if allowed, must be tested. The face coverings may not have exhalation valves. If the device requires replaceable filters, they have to be designed so they cannot be inserted improperly. Transparent parts are allowed if the design allows enough filtration to provide the source control function.
Labeling requirements include manufacturer’s name, model or style number and a citation of meeting the ASTM F3502 standard. An additional product use document/packaging statement about the limits of the CFC shall also be included if the device is not also dual certified as a medical mask or a respirator, and several other requirements to meet traceability, sizing, care and use and legislative requirements for garments.
Test Labs Qualified to Perform the Testing
Labs which perform this testing are required to be ISO 17025 accredited for the testing and the manufacturer must meet the ASTM F3050 quality control measures. ISO 9001 labs do not have the competency requirements for this type of testing.
This article originally appeared in the July/August 2021 issue of Occupational Health & Safety.