NIOSH Expands its CBRN Air-Purifying Respirator Protection List


Protecting Emergency Responders by Evaluating New and Emerging CBRN Hazards

By Mr. Jon Szalajda, Deputy Director and Dr. Lee Greenawald, Physical Scientist, NPPTL, NIOSH

Emergency responders rely on NIOSH-approved respirators to protect themselves from respiratory hazards. One such option includes NIOSH-approved respirators equipped with chemical, biological, radiological, and nuclear (CBRN) canisters. As part of a NIOSH-approved CBRN air-purifying respirator (APR), air-purifying escape respirator (APER), or powered APR (PAPR), the CBRN canister provides protection against dozens of CBRN hazards that may be present in an emergency environment. Importantly, APERs are designed and approved for escaping from, and not entering, a workplace where CBRN hazards above the immediately dangerous to life or health levels are suspected.

NIOSH categorizes CBRN hazards into seven different chemical families. In 2001, this hazard assessment concluded with 139 hazards identified across the seven chemical families, formally called the NIOSH CBRN APR Protection List (NIOSH 2005, NIOSH 2018). NIOSH uses 11 chemicals—known as test representative agents (TRAs)—to test the protective ability of a canister claiming CBRN protections for APRs, APERs, and PAPRs against the identified hazards within these seven families.

Since 2001, CBRN hazards have evolved in type, usage, and dissemination (Greenawald et al. 2020). Further, hazard assessment modeling has become much more sophisticated, and the understanding of filtration science has vastly improved. Therefore, in 2016, NIOSH initiated a project to conduct an updated CBRN hazard assessment to identify and evaluate new/emerging chemical and radiological hazards to ensure the 11 TRAs selected in 2001 are still representative of all hazards.

These chemical and radiological hazards were anticipated to be categorized into one of NIOSH’s seven chemical families: Organic Vapor, Acid Gas, Base Gas, Hydride, Formaldehyde, Nitrogen Oxide, or Particulate Family. The process undertaken and the findings of this updated hazard assessment are summarized below.

Summary of the Updated CBRN Hazard Assessment Methodology

To complete this updated CBRN hazard assessment, NIOSH partnered with the Department of Homeland Security (DHS) and the Department of Defense (DOD). DHS Chemical Security Analysis Center scientists, who have extensive expertise in homeland security chemical threats and risks, reviewed chemical hazard assessments using state-of-the-art modeling tools and updated the list of chemical and radiological hazards. DOD Chemical Biological Center scientists partnered with NIOSH scientists to interpret the hazard assessments and applied cutting-edge filtration theory science and filtration empirical data to evaluate the anticipated canister filtration capabilities.

NIOSH also provided expertise drawn from NIOSH’s Respirator Approval Program regarding minimum NIOSH performance and design requirements for CBRN respirators, CBRN Statements of Standard, and current commercially available NIOSH-approved APRs with CBRN protections needed for testing. The project team included several participants from the initial 2001 hazard assessment

NIOSH and its partners first identified and compiled chemical and radiological hazards by reviewing five recent risk-based hazard assessments available to the DOD and DHS. The group then developed a four-step evaluation process to assess each identified hazard:

1. evaluating its chemical and physical properties,

2. evaluating its actual or anticipated filtration behavior within the CBRN canister (i.e., physical adsorption, chemisorption, or mechanical filtration),

3. categorizing it into one of NIOSH’s Chemical Families, and

4. comparing it against the existing TRAs in its respective Chemical Family to determine the need for additional test agents.

Updated CBRN Hazard Assessment Findings

A full description of the assessment findings appeared in a Journal of Occupational and Environmental Hygiene article (Greenawald et al. 2020). A summary of the CBRN hazard assessment evaluation steps and corresponding results can be seen in Figure 1.

Based on a review of recent hazard assessments for respiratory hazards relevant to the emergency responder, the team identified a total of 238 hazards (192 chemicals and 46 radiological). The team identified an additional 14 classified chemicals—i.e., those that are restricted to personnel with necessary security clearance—that will not be discussed in this article due to their sensitive nature. The original 2001 NIOSH hazard assessment previously identified 36 of the 238 chemicals as part of NIOSH’s CBRN APR Protection List (NIOSH 2005). Of the 238 hazards, 207 hazards were ultimately grouped into one of the existing seven NIOSH Chemical Families: 66 in the Organic Vapor Family, 29 in the Acid Gas Family (including two radiological vapors), 4 in the Base Gas Family, 1 in the Formaldehyde Family, 3 in the Nitrogen Oxide Family, 2 in the Hydride Family, and 102 in the Particulate Family (including most of the radiological particulates). These hazards were added to the existing 2001 NIOSH CBRN APR Protection List, bringing the total to 286 hazards on this list.

Some hazards could not be initially categorized due to being too unstable in the emergency responder operational environment (e.g., they decompose quickly) or requiring further testing and evaluation to confirm their categorization into a NIOSH Chemical Family. Six hazards underwent additional testing, where NIOSH ultimately determined it was appropriate to categorize these six hazards within the existing seven NIOSH Chemical Families (Greenawald et al. 2020). Table 1 lists a comparison between the 2001 and updated NIOSH CBRN APR Protection List.

Table 1: Summary of the original and updated NIOSH CBRN APR Protection List. TRA=test representative agent.

The project’s findings showed that NIOSH’s TRAs remain representative of the newly identified hazards and ultimately provided confidence to the nation’s emergency responders that NIOSH-approved respirators with CBRN canisters continue to provide the necessary protection against the latest identified chemical and radiological threats. Additionally, a standardized methodology was developed to conduct future CBRN hazard assessments, which will be highly valuable to future researchers across federal agencies.

Figure 1: Overall summary of the CBRN hazards evaluation process and results.

During the described 2018 CBRN chemical and radiological hazard assessment, researchers identified several particulate illicit drugs but did not perform an in-depth analysis of these drugs and their precursors for non-CBRN respirators or other types of PPE. NIOSH and its partners seek to expand upon the 2018 CBRN assessment with a specific focus on identifying new and emerging illicit drugs and their precursors for future proactive emergency response activities. Using the evaluation framework developed in the 2018 study, current, new, and emerging illicit drugs will be similarly theoretically assessed to inform PPE performance vulnerabilities, research gaps, standards development needs, and any necessary changes to current federal PPE guidance and recommendations for illicit drugs. This work is ongoing.


After reviewing each of the identified 238 chemical and radiological hazards, researchers found that the current NIOSH 11 CBRN TRAs continue to represent the known CBRN hazards relevant to the emergency responder and should remain the basis for NIOSH respirator approval testing for respirators claiming protections against CBRN hazards. Thus, no changes were needed to NIOSH’s original 11 CBRN TRAs or NIOSH’s CBRN APR, APER, or PAPR Statements of Standard. However, because of the described evaluation, NIOSH has expanded its original CBRN APR Protection List of 139 hazards to include those additional hazards identified—i.e., NIOSH’s CBRN APR Protection List now numbers 286 total hazards. The NIOSH CBRN TRAs and the full list of 238 hazards in each NIOSH Chemical Family, constituting NIOSH’s updated CBRN APR Protection List, can be seen at NIOSH’s CBRN Respirator Approval Resources webpage. Hazard assessment evaluation work for illicit drugs is ongoing.



NIOSH CBRN Respirator Approval Resources

NIOSH CBRN Respiratory Protection Handbook

NIOSH CBRN Statement of Standard

NIOSH Respirator Fact Sheet

NIOSH Interim Guidance on the use of CBRN Full Facepiece, Air-Purifying Respirators/Gas Masks Under 42 CFR Part 84 Lee A. Greenawald, Christopher J. Karwacki, Frank Palya, Matthew A. Browe, David Bradley & Jonathan V. Szalajda [2020] Conducting an evaluation of CBRN canister protection capabilities against emerging chemical and radiological hazards, Journal of Occupational and Environmental Hygiene, 17:10, 480-494, DOI: 10.1080/15459624.2020.1798452

About the Authors

Lee Greenawald, Ph.D. is a Physical Scientist with the National Personal Protective Technology Laboratory (NPPTL) of the National Institute for Occupational Safety and Health (NIOSH). Lee received her B.S. in Forensic Chemistry from Ohio University and a Ph.D. in Analytical Chemistry from West Virginia University. Lee has conducted various post-market research efforts regarding the performance of personal protective equipment (PPE), such as evaluating stockpiled respirators and surgical gowns after long-term storage, respirators when challenged against emerging chemical threats, and gloves when challenged with illicit drugs. Her current role includes various respirator research and certification activities as part of NIOSH’s Respirator Approval Program.

Jonathan (Jon) Szalajda became the Deputy Director for the National Personal Protective Technology Laboratory (NPPTL) division of NIOSH in September 2015. Since joining NPPTL in 2001, Jon has held various leadership roles in the organization.  Some of his duties included being responsible for developing and promulgating new approval Personal Protective Equipment (PPE) related standards and regulations, including NIOSH’s Chemical, Biological, Radiological, and Nuclear (CBRN) respirator standards. Prior to coming to NIOSH, Jon was a proposal manager for Bombardier Transportation and was the systems manager for the M40 Mask program with the Department of the Army.  He holds a BS degree in Chemical Engineering from Penn State and MS degrees in engineering from the George Washington University and the University of Pittsburgh.  He has worked in the fields of respiratory protection and PPE for over 35 years.  Jon is currently a member of NFPA Respiratory Protection Technical Committees, the Vice-Chairman of the ASTM F23.65 committee on Respiratory Protection, and a past president of the AIHA Respiratory Protection Committee.

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