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Notice of Opportunity for Public to Provide NIOSH with Comment: Positive-Pressure Closed-Circuit Self-Contained Breathing Apparatus

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Information about this document as published in the Federal Register.

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The National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC), Department of Health and Human Services.


(1) Notice of opportunity for public to provide NIOSH with comment on the public's reevaluation of NIOSH limitations on and precaution for safe use of positive-pressure closed-circuit self-contained breathing apparatus, Authority: Public Law 91-596.(2) Notice of opportunity for manufacturers and stakeholders to provide NIOSH with input on the NIOSH prohibition against using a respirator which uses a breathing gas of pure oxygen during direct exposure to open flames and/or high radiant heat.


The NIOSH, National Personal Protective Technology Laboratory (NPPTL), is currently reevaluating its limitations on and precaution for safe use of positive-pressure closed-circuit self-contained breathing apparatus. As stated in the Federal Register (Vol. 50, No. 222, pages 47456-47457 dated Monday, November 18, 1985) NIOSH's position on this topic is that:

Available information does not demonstrate to the satisfaction of NIOSH that positive-pressure closed-circuit self-contained breathing apparatus which use a breathing gas of pure oxygen can be used during direct exposure to open flames and/or high radiant heat and assure the wearer's safety. Therefore, NIOSH has determined that until it has been demonstrated to the satisfaction of NIOSH that those devices can be worn under such conditions, it is prudent to presently limit the use of positive-pressure closed-circuit self-contained breathing apparatus which use pure oxygen breathing gas to mines and mining atmospheres which do not involve exposure to open flames or high radiant heat.

Background: NIOSH/NPPTL is currently developing performance concepts as part of the rulemaking process to develop a Closed-Circuit Self-Contained Breathing Apparatus (CC-SCBA) Module. This process has identified that flame and heat durability requirements need to be considered as part of the module. On possible inclusion to the requirements is the National Fire Protection Agency (NFPA) Heat and Flame Test, NFPA 1981, Section 8.11. NIOSH has conducted laboratory testing on two (2) different manufacturer's apparatus. In the initial testing, NFPA testing procedures were followed with the exception that a “dummy” cylinder was used in lieu of the oxygen cylinder. Test results were encouraging and were presented at NIOSH/NPPTL public meetings held on July 19, 2005 and on October 12, 2006. Arrangements are being made to conduct the same tests with full oxygen cylinders.

Additional research was garnered through testing conducted at a second laboratory. NPPTL personnel witnessed a Flame Engulfment Test. In Germany, Department 8 of the Association for the Promotion of German Fire Safety (VFDB) has included in its Guideline 0802 the same requirements for Close-Circuit Breathing Apparatus that has been written into the draft European Standard EN137 for Open-circuit Compressed Air Breathing Apparatus for flame engulfment. In this Directive, if special thermal loads for protective equipment cannot be excluded during tactical operation, the device must pass the flame engulfment test which is described in Appendix D. Their flame engulfment test is similar to NFPA's. In addition, this directive requires that when using closed-circuit compressed air breathing apparatus, type positive pressure with mixed gas supply (N2, O2) with an oxygen content of ≥ 30% by volume in the breathing circuit risks by oxygen emerging from a leakage in the mask cannot be excluded. These devices must pass the oxygen flame engulfment test procedure described in appendix G as follows:

  • Simulate possible oxygen enrichment under a firefighter helmet according to EN 443 through a defined leakage in the respiratory protective mask (2.5 mm, 10 mm above the right temple strap). The test set-up simulates real conditions by equipping the test head with real hair, a flame protection hood and the respective neck curtains.
  • Flame engulfment test is in accordance with Appendix D

○ Device is attached to a test dummy and preheated in an oven at 90 ± 5° C for 15 minutes

○ Complete unit is then exposed to direct flames for 10 seconds

○ Test dummy with the apparatus is then lifted to 150 ± 5/0 mm and dropped

○ During the entire test, the device is connected to a breathing machine. The pass/fail criteria are:

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  • Device must not continue to burn for more than 5 seconds
  • No component that secures the device to the user's body or that secures the cylinder must come off or be displaced
  • Breathing resistance as per EN 137 are met
  • The test head must not continue to burn for more than 5 seconds.

The closed-circuit self-contained breathing apparatus used in the test witnessed by NIOSH/NPPTL personnel successfully passed all of the listed criteria.

Additionally, the National Institute of Standards and Technology (NIST), Building and Fire Research Laboratory, Fire Research Division has provided a computational fluid dynamic (CFD) study of oxygen dissipation into the environment surrounding a respirator facepiece. For this study, 3-dimensional scans were taken of actual heads and masks for use in the CFD software. Leak geometries representing an imperfect seal were defined. Other variables included oxygen concentration fields and flow streamlines for multiple combinations of fuel and air in the surrounding environment, content of the leak, various breathing patterns, etc. Conclusions reached during the study were:

  • Oxygen expelled through leak in respirator is propelled away from head region through advection and dissipates through diffusion.
  • Risk of flammable mixture near head is observed in 10% propane environment.
  • This is an extreme environment (fuel-rich, near flammable mixture.)
  • In case of flammable environment, oxygen leak results in small, fuel-lean region near head.
  • In fuel-lean environment, oxygen further decreases fuel concentration.

NIST Technical Note 1484 titled, “A Computational Model of Dissipation of Oxygen from an Outward Leak of a Closed-Circuit Breathing Device” available through the internet at this link,​bfrlpubs/​fire07/​PDF/​f07024.pdf chronicles the research work completed by NIST.

Through this announcement, NIOSH/NPPTL is seeking input from stakeholders and manufacturers to determine the following:

1. Opinion on the current prohibition.

2. Provide supporting data to maintain, modify, or rescind the current prohibition.

3. If additional research is needed to support rescinding the prohibition, what would it entail?

4. Willingness to participate in a collaborative agreement with NIOSH/NPPTL to conduct research on this topic and support willing to provide.

5. Other comments on the subject.

Public Comment Period: Submit input to the NIOSH Docket Office within 60 days after the date of publication of this notice in the Federal Register. Reference Docket Number NIOSH-123 in comments.


Input can be submitted by:

  • Mail: NIOSH Docket Office, Robert A. Taft Laboratories, M/S C 34, CC SCBA O2 Prohibition—NIOSH Docket Number 123, 4676 Columbia Parkway, Cincinnati, OH 45226.
  • E-mail:
  • Fax: (513) 533-8285.
  • Phone: (513) 533-8303.
  • NPPTL Web Site:​niosh/​npptl.

Contact Person for Technical Information: Timothy R. Rehak at 412-386-6866 or e-mail:

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Dated: January 16, 2008.

James D. Seligman,

Chief Information Officer, Centers for Disease Control and Prevention.

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[FR Doc. E8-1273 Filed 1-24-08; 8:45 am]