Part A. Personal protective equipment is divided into four categories based on the degree of protection afforded. (See Part B of this appendix for further explanation of Levels A, B, C, and D hazards.)
The following constitute Level A equipment; it may be used as appropriate;
1. Positive pressure, full face-piece self-contained breathing apparatus (SCBA), or positive pressure supplied air respirator with escape SCBA, approved by the National Institute for Occupational Safety and Health (NIOSH).
II. Level B - The highest level of respiratory protection is necessary but a lesser level of skin protection is needed.
The following constitute Level B equipment; it may be used as appropriate.
1. Positive pressure, full-facepiece self-contained breathing apparatus (SCBA), or positive pressure supplied air respirator with escape SCBA (NIOSH approved).
III. Level C - The concentration(s) and type(s) of airborne substance(s) is known and the criteria for using air purifying respirators are met.
The following constitute Level C equipment; it may be used as appropriate.
1. Full-face or half-mask, air purifying respirators (NIOSH approved).
IV. Level D - A work uniform affording minimal protection: used for nuisance contamination only.
The following constitute Level D equipment; it may be used as appropriate:
3. Boots/shoes, chemical-resistant steel toe and shank.
4. Boots, outer, chemical-resistant (disposable).(1)
5. Safety glasses or chemical splash goggles.(1)
6. Hard hat.(1)
7. Escape mask.(1)
8. Face shield.(1)
Footnote(1) Optional, as applicable.
Part B. The types of hazards for which levels A, B, C, and D protection are appropriate are described below:
I. Level A - Level A protection should be used when:
1. The hazardous substance has been identified and requires the highest level of protection for skin, eyes, and the respiratory system based on either the measured (or potential for) high concentration of atmospheric vapors, gases, or particulates; or the site operations and work functions involve a high potential for splash, immersion, or exposure to unexpected vapors, gases, or particulates of materials that are harmful to skin or capable of being absorbed through the skin,
2. Substances with a high degree of hazard to the skin are known or suspected to be present, and skin contact is possible; or
3. Operations must be conducted in confined, poorly ventilated areas, and the absence of conditions requiring Level A have not yet been determined.
II. Level B protection should be used when:
1. The type and atmospheric concentration of substances have been identified and require a high level of respiratory protection, but less skin protection.
2. The atmosphere contains less than 19.5 percent oxygen; or
3. The presence of incompletely identified vapors or gases is indicated by a direct-reading organic vapor detection instrument, but vapors and gases are not suspected of containing high levels of chemicals harmful to skin or capable of being absorbed through the skin.
Note: This involves atmospheres with IDLH concentrations of specific substances that present severe inhalation hazards and that do not represent a severe skin hazard; or that do not meet the criteria for use of air-purifying respirators.
III. Level C - Level C protection should be used when:
1. The atmospheric contaminants, liquid splashes, or other direct contact will not adversely affect or be absorbed through any exposed skin;
2. The types of air contaminants have been identified, concentrations measured, and an air-purifying respirator is available that can remove the contaminants; and
3. All criteria for the use of air-purifying respirators are met.
IV. Level D - Level D protection should be used when:
1. The atmosphere contains no known hazard; and
2. Work functions preclude splashes, immersion, or the potential for unexpected inhalation of or contact with hazardous levels of any chemicals.
Note: As stated before, combinations of personal protective equipment other than those described for Levels A, B, C, and D protection may be more appropriate and may be used to provide the proper level of protection.
As an aid in selecting suitable chemical protective clothing, it should be noted that the National Fire Protection Association (NFPA) has developed standards on chemical protective clothing. The standards that have been adopted by include:
NFPA 1991 - Standard on Vapor-Protective Suits for Hazardous Chemical Emergencies (EPA Level A Protective Clothing)
NFPA 1992 - Standard on Liquid Splash-Protective Suits for Hazardous Chemical Emergencies (EPA Level B Protective Clothing)
NFPA 1993 - Standard on Liquid Splash-Protective Suits for Non-emergency, Non-flammable Hazardous Chemical Situations (EPA Level B Protective Clothing)
These standards apply documentation and performance requirements to the manufacture of chemical protective suits. Chemical protective suits meeting these requirements are labeled as compliant with the appropriate standard. It is recommended that chemical protective suits that meet these standards be used.
[59 FR 43268, Aug. 22, 1994]
Jonathan V. Szalajda, MS
This blog highlights the advancements made in respiratory protection for workers in the event of chemical, biological, radiological, and nuclear (CBRN) emergencies.
NIOSH research into the specific needs of responders to terrorist events began with the co-sponsoring of the Chemical and Biological Respiratory Protection Workshop with the Department of Defense (DOD) and the Occupational Safety and Health Administration (OSHA) in March 1999. Following the World Trade Center attack, NIOSH partnered with its stakeholders and RAND to assess the range of areas, including respiratory protection, in which advancements to protect responders were needed. Findings and recommendations from that assessment are published in four NIOSH/RAND reports:
- Protecting Emergency Responders: Lessons Learned from Terrorist Attacks
- Protecting Emergency Responders, Volume 2: Community Views of Safety and Health Risks and Personal Protection Needs
- Protecting Emergency Responders, Volume 3: Safety Management in Disaster and Terrorism Response
- Protecting Emergency Responders: Volume 4: Personal Protective Equipment Guidelines for Structural Collapse Events
Since then, NIOSH has developed a systematic approach to identify the hazards that responders would face, assess the capabilities of existing respiratory protection equipment to provide protection against viable threats using benchmark testing, and set certification standards that stretch the capabilities of the protective technologies to enhance the protection offered to responders during CBRN events.
The standards development and respirator certification programs conducted at the NIOSH National Personal Protective Technology Laboratory (NPPTL) have led to an increase in the national inventory of NIOSH-approved respirators with CBRN protection capabilities.
Respirator Performance and Capabilities
Under the Occupational Safety and Health Act and the Mine Safety and Health Act, NIOSH has tested and certified respirators for more than three decades to protect workers from harmful airborne contaminants.
In traditional work settings such as factories and mines, respirators are used as one component of a strategic program to protect workers from a known hazard. The challenge of protecting emergency responders is quite different in a scenario in which the hazards from a potential terrorist attack may not be known, especially at the outset. What toxic chemical, biological, or radioactive contaminants may have been released in the attack, and at what concentrations?
The assessment of the type and magnitude of the respiratory threats potentially faced by responders of a terrorist event led to the establishment of eleven Test Representative Agents (TRAs) and test concentrations that NIOSH uses in benchmark testing to assess present technologies’ ability to protect responders from likely threats. NIOSH benchmark testing, conducted prior to the attacks of 9/11, demonstrated that neither industrial nor military respirators provided protection against the full range of known or projected CBRN terrorist threats.
The development and implementation of standard test procedures since then, along with minimum requirements for the construction and performance of respirators, has enabled NIOSH to establish approval criteria for respiratory protection equipment that will withstand the anticipated threats of a terrorist event during response and recovery activities. In response to responders’ requests for assurance of performance, these criteria include performance tests against chemical warfare agents (Live Agent Testing) conducted by U.S. Army test laboratories, to verify that respirators will provide needed protection against those chemical threats.
Through the development and implementation of the NIOSH CBRN respirator performance criteria, respirators are more protective for user safety and health in a variety of emergency response situations when the respirator is certified to NIOSH CBRN protections. Implementation of these criteria through the use of regulations and standards results in overall improvements for performance, reliability, and safety of respirators.
Respirator Testing and Certification: The First CBRN Standard
Since December 2001, NIOSH has established approval criteria and approved respiratory protection equipment for five types of respirators that provide protection against CBRN agents. NIOSH has issued 91 approvals for the various respirator types for which approval standards have been implemented. These approved products include:
Respirator Type (CBRN)
Date of Final Standard
Number of NIOSH Approvals Issued
Open-Circuit Self Contained Breathing Apparatus (SCBA)
Air-Purifying Respirators (APR)
Air-Purifying Escape Respirators (APER)
Closed-Circuit Escape Respirators (CCER)
Powered Air-Purifying Respirators (PAPR)
Based on concerns raised by the International Association of Fire Fighters (IAFF), the National Fire Protection Association (NFPA), and the International Association of Fire Chiefs (IAFC), NIOSH, along with its standards development partners, the U.S. Army Soldier and Biological Chemical Command (now known as Edgewood Chemical Biological Center) and the National Institute of Standards and Technology (NIST), determined that the open-circuit, pressure demand/positive pressure Self Contained Breathing Apparatus (SCBA) would receive first priority for CBRN terrorism agent protection.
Reflecting the stakeholders’ concerns, NIOSH decided to give this type of respirator first priority because it is used where the respiratory threat level is unknown or known to be immediately dangerous to life and health (IDLH).
NIOSH’s approval for CBRN protection is referenced in the National Fire Protection Association (NFPA) 1981 Standard, Open Circuit SCBA for Emergency Services (2007 edition). In order to meet this current edition of the NFPA standard, all new SCBA must be CBRN-certified by NIOSH. The coordination with NFPA has resulted in enhanced collaboration between NIOSH and the certification bodies for issuance of the certification to NFPA 1981 requirements. U.S. fire departments purchase and use SCBA certified to meet the NFPA 1981 standard, thereby providing responders in those organizations with this added level of protection. on new units purchased since 2008.
The Second CBRN Standard
The second CBRN standard to be developed was for full-facepiece, air-purifying respirators (APR). The CBRN APR full-facepiece respirator is widely used by multiple responder groups. It provides a lower level of protection than the SCBA and its use is generally allowed once conditions are understood and exposures are determined to be at levels below those considered to be IDLH.
In response to stakeholder feedback, interoperability among air purifying elements and communications testing in the form of a speech intelligibility test, performed while wearing a respirator, have been incorporated into the respirator performance standards.
The speech intelligibility test has been incorporated into the approval criteria for the subsequently-announced respirator types as well.
NIOSH responded to the need for interoperability among air purifying elements for APRs by specifying certain construction and performance parameters that enable the interoperability of gas and vapor-removing air-purifying elements (canisters) with facepiece components from different manufacturers.
Parameters including canister size, weight, airflow resistance, capacity for gas and vapor absorption, connection-to-facepiece dimensions, and position-on-the-facepiece dimensions had to be specified to enable the safe interchange of components between various manufacturers.
Although the NIOSH approval does not allow intermixing of different manufacturers’ CBRN canisters and facepieces, these controls enable incident commanders to allow limited interchange of components at the time of supply shortages during an emergency response.
Additionally, in response to responders concerns, NIOSH supported modifications to the 2007 edition of NFPA 1982, Personal Alert Safety Systems, containing revisions that provide for strengthened performance requirements and testing regarding alarm signal degradation.
The third priority for CBRN standards was the air-purifying and self-contained escape respirators to enable the general worker population to egress safely from a potential CBRN terrorist incident. To provide another option for multiple responder groups, which also provides a higher level of protection compared to APRs, the CBRN PAPR standards development was identified as the fourth priority for standard development and implementation. The PAPR standards also addressed the identified needs and concerns of the First Receivers in the medical community.
NIOSH continues to develop approval criteria for additional types of respirators in response to responders’ needs for appropriate respiratory protection against the anticipated hazards faced in performing rescue and recovery operations resulting from viable terrorist threats, as well as HAZMAT incidents. New approval criteria to include CBRN protections are actively under development in NIOSH’s NPPTL Policy and Standards Development Branch for the following respirator types:
Closed-Circuit Self Contained Breathing Apparatus (CC-SCBA)
Supplied Air (Airline) Respirators (SAR)
Updated Powered Air-Purifying Respirators (PAPR)
Mr. Szalajda is the Branch Chief for Policy and Standards Development in the NIOSH National Personal Protective Technology Laboratory.