The national Institute for Occupational Safety and Health (NIOSH) – National Personal Protective Technology Laboratory (NPPTL) of the Centers for Disease Control and Prevention (CDC) is responsible for the conformity assessment of respirators used in occupational settings. Conformity assessment encompasses preapproval testing and quality assurance evaluations and includes postapproval product and site audits. The stringency of this comprehensive approval process assures that once a respirator has earned NIOSH approval the user can be confident that the device will provide the expected level of protection, as long as it fits properly and is selected, maintained, and worn correctly. The Occupational Safety and Health Administration (OSHA) requires that only NIOSH-approved respirators be used in US workplaces.¹

It had been projected that during a public health emergency the supply of N95 respirators may become strained,^2,3 and, indeed, a global shortage of NIOSH-approved N95 filtering facepiece respirators was experienced during the coronavirus disease 2019 (COVID-19) pandemic.⁴ Given the high demand for respiratory protective devices (RPDs) by healthcare personnel, the shortage prompted several governmental and nongovernmental organizations to implement strategies to conserve the limited supply of NIOSH-approved respirators. Such strategies included control banding, a technique used to guide the assessment and management of workplace risks⁵; extended use and limited reuse of N95 respirators^6,7,8; the use of respirators beyond their shelf life stored in strategic stockpiles⁹; decontamination of respirators¹⁰; and the use of NIOSH-approved respirators designed to be reused, such as elastomeric and powered air-purifying respirators.¹¹

These strategies have not been enough to meet the demand for respiratory protection during the COVID-19 pandemic due to the increased use of RPDs beyond acute hospital care settings, such as nursing homes and ambulatory care clinics. Additional crisis strategies were, therefore, needed. To increase the availability of RPDs, the CDC¹² and the US Food and Drug Administration (FDA)^13,14 implemented a crisis strategy to permit the occupational use of non-NIOSH-approved RPDs designed to meet international standards that incorporate requirements similar to NIOSH-approved N95 respirators.¹⁵ To inform this process, NPPTL recommended the use of performance standards that specified protection factors of at least 10* from 7 international organizations associated with Australia, Brazil, China, Europe, Japan, Korea, and Mexico.¹² It further recommended that non-NIOSH-approved RPDs developed by manufacturers that were not NIOSH approval holders should be used only in crisis situations when no other NIOSH-approved N95 respirator or respirator produced by a NIOSH approval holder is available. At the same time, because of the shortages experienced during the COVID-19 pandemic, OSHA relaxed its enforcement guidelines around RPDs used in occupational settings.¹⁶

The primary mechanism used to implement these crisis strategies during the COVID-19 pandemic was a series of emergency use authorizations (EUAs) issued by the FDA.¹³ An initial EUA was issued on March 24, 2020, for specified disposable RPDs. A separate EUA for certain disposable RPDs manufactured in China was issued on April 3, 2020.¹³ To be eligible, respirators had to meet specified criteria.^† Authorized filtering facepiece respirators meeting the specified criteria were included in Appendix A of the EUA. Shortly after the April 3, 2020, EUA was issued, nearly 90 Chinese manufacturers were included in Appendix A.¹⁷

In response to public inquiries and concerns regarding the quality of international RPDs temporarily authorized for occupational use,^‡ NIOSH developed a supplemental filtration performance assessment process.¹⁸ The NIOSH testing incorporated a modified version of NIOSH Standard Test Procedure TEB-APR-STP-0059.^§ The abridged test included a focused assessment of the particulate filtration (air-purifying) efficiency of RPDs. Inhalation and exhalation resistance were not included.

The test was developed to rapidly evaluate the filtration efficiency of international RPDs temporarily authorized for emergency use in occupational settings for the health and safety benefit of US workers and to transparently communicate the test results. NPPTL received requests directly from federal, state, and local government agencies, healthcare providers, employers in nonhealthcare industries, public safety and first responder organizations, and universities.^** Information such as the manufacturer name, model designation, and performance standard under which the RPDs were reportedly manufactured were required components of the request.

For each valid request received, a minimum of 10 RPDs (of the same model and from the same manufacturer) were tested. The sampling protocol used to select the 10 RPDs was at the discretion of the group making the request; however, requestors reported using both a convenience, nonprobability sampling technique (in which samples were drawn from the population based on their availability) or a random sampling technique (in which each unit in the defined population has an equal probability of being selected for testing).

After NIOSH testing was complete, results were communicated to the requesting group through a formal report and were publicly released online.¹⁹ The reports included basic information about the RPD evaluated (eg, manufacturer name, model information, international standard claim), photographs, and the results for the sample RPDs tested. The results were also openly and rapidly shared with the FDA to aid the collaborative process of continually improving the EUAs.

The results included the maximum and minimum filtration efficiencies observed among the RPDs tested.^†† By reporting the maximum and minimum efficiencies, the observed range in filtration efficiency could be computed. The range indicates the consistency of filtration efficiency between the units evaluated. Understanding the consistency in filtration efficiency is important because users must be able to trust that individual units, which are labeled and packaged identically, provide a consistent level of performance when respiratory hazards are encountered in the workplace. Further, as required in 42 CFR 84,²⁰ NIOSH-approved N95 filtering facepiece respirators consistently filter out at least 95% of particulate matter, and the strategy to supplement the national supply with international RPDs includes an expectation of a similar level and consistency in filtration efficiency.

NPPTL received valid requests for testing nearly immediately after initiating the supplemental performance assessment process. The first NIOSH test was completed on April 10, 2020, 1 week after the EUA was issued. By the end of April 2020, NIOSH tests for approximately 80 distinct sets of international RPDs were completed. The test results revealed quality concerns related to both the level and consistency of observed filtration efficiency. In part due to these findings, on May 7, 2020, the FDA revised the EUA for RPDs manufactured in China by removing many of the manufacturers and models initially included in Appendix A.¹⁷ In addition, the FDA and NPPTL further partnered to heighten the role of NIOSH testing and increase the surveillance of all RPDs imported from China.¹³ The testing procedure was revised to increase the sample size and statistical power and to emphasize random sampling, thereby enhancing the ability of each test to uncover distinct pockets of filtration performance within consistently labeled RPDs.

After the April 3, 2020 EUA was revised on May 7, 2020, NIOSH testing results were categorized in 2 phases: Phase 1 included tests completed up to May 6, 2020, and Phase 2 included tests completed between May 7 and August 17, 2020.

This case study represents an interagency collaboration designed to support the health and safety of the US workforce throughout the COVID-19 pandemic. The NIOSH supplemental testing of international RPDs filled a critical gap during the COVID-19 pandemic by communicating evidence-based test results within 1 week (usually within 48 hours of the units being received) to the public and other agencies involved with the response.²¹ These results directly contributed to FDA continuously updating the EUAs to add and remove RPDs authorized for use in healthcare settings. A third phase of NIOSH testing is underway, representing a continuation of the supplemental testing of non-NIOSH-approved RPDs that continue to be listed on the FDA’s EUA.

Although NPPTL has conducted an extensive number of tests of international RPDs, other entities have conducted similar tests. Across the country, state governments have partnered with universities and third-party laboratories to evaluate the performance of RPDs conforming to international standards to inform purchasing decisions or remove substandard products from the market—all for the benefit of the US workforce in need of RPDs during the pandemic.²² The Massachusetts Institute of Technology and Harvard University, for example, found that many of the filtering facepiece respirators available for procurement during the COVID-19 pandemic do not provide levels of fit and filtration similar to those of NIOSH-approved N95 respirators.^23,24 The NPPTL procedure provides a consistent protocol for evaluating these devices and enables third-party laboratories and other organizations to conduct the testing on their own.²⁵ As the COVID-19 pandemic continues, testing will remain important to the health and safety of the US workforce.

Several limitations should be noted. First, given that a random sampling technique could not be guaranteed, the test results are generalized to the sample of international RPDs tested and may not be representative of a larger sample. Second, the tests were designed to provide a rapid evaluation of the filtration efficiency only. Given that a standard NIOSH approval evaluation consists of additional performance tests, as well as a comprehensive quality assurance review of the quality process and manufacturing site, any type of comparison between the international devices assessed and NIOSH-approved N95 respirators is not possible. In addition, certificates of approval or validation of conformance with an international standard were not provided with the samples. The authenticity of a claim that a product met or did not meet a particular international standard could, therefore, not be made.

Given these limitations, the results suggest that a substantial proportion of RPDs tested did not provide consistent filtration protection above 95% when evaluated using an adapted version of NIOSH’s test method. While the international RPDs are not a precise equivalent, the standards considered incorporate filtration efficiency specifications that are nearly equivalent to NIOSH’s requirement for N95s to have at least 95% filtration efficiency. There are several possible reasons why the products assessed did not perform to these expectations. First, companies newly established to meet the global demand for RPDs during the COVID-19 pandemic may not have had the time or opportunity to establish quality control systems needed to consistently produce high-performing RPDs. Second, shortages or an inconsistent supply of the raw materials needed to produce high-performing RPDs may have forced manufacturers to procure lower-performing filtration material. Third, several counterfeit reports were received by NPPTL. In such cases, documents may have been altered to make RPD models appear to comply with a standard when they do not, or manufacturers’ names, logos, and model numbers may have been misrepresented or counterfeited. For questions regarding product authenticity and potential counterfeiting, consumers are urged to directly contact the manufacturers and others involved in the supply chain.

Potential purchasers of international RPDs should refer to the CDC and NIOSH websites for guidance on how to evaluate respirators from other countries to determine if they provide adequate protection before making purchasing decisions. Consumers are urged to consult the FDA’s current EUAs and the results of NPPTL supplemental performance assessments.²⁰