Letters of Interpretation

OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. Each letter constitutes OSHA's interpretation of the requirements discussed.

Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information.

These letters of interpretation and the standards they address may not apply to OSHA State Plans. State Plans are required to have standards and enforcement programs that are at least as effective as OSHA's and may have different or additional requirements. Please see OSHA-approved State Plans for more information.

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Date Title Standard Number
Clarification on the use of smoke escape hoods/masks by area monitors during a building evacuation. 1910.134
Clarification on firefighters with facial hair who enter IDLH atmospheres and use a self-contained breathing apparatus. 1910.134, 1910.134(g)(1)(i)(A)
Use of smoke escape hoods meeting the ANSI-ISEA standard 1910.134, 1910.134(c)(2), 1910.134(d)(2)(ii), 1910.134(k), 1910.134 App D
OSHA Training Standards Policy Statements 1910.134(k), 1910.147(c), 1910.1030(g), 1910.1200(h), 1926.21
Clarification of OSHA's position on preemption precluding state court findings with regard to defective NIOSH-certified respirators. 1910.134
Definition of a single use and negative pressure respirator 1910.134
Clarification on equivalent test nebulizer for qualitative fit tests. 1910.134
Difference between voluntary and non-voluntary use of a respirator. 1910.134
Maintenance of medical evaluation and fit test records as required by the Respiratory Protection Standard. 1910.134, 1910.134(m), 1910.1020
Clarification of OSHA denial of FirePASS's variance request and respiratory protection requirements in oxygen-deficient atmospheres. 1910.134, 1910.134(d)(2)(iii)
Tuberculosis and Respiratory Protection Enforcement 1910.134, 1910.134(f)(2)
Clarification on whether to use quantitative or qualitative fit-testing for full-facepiece PAPRs. 1910.134, 1910.134(f)(8)
Requirement for employer to assess potential hazards of handling trailer debris to provide necessary PPE and hazard communication information to affected employees. 1910.120(q), 1910.132, 1910.134(a)(2), 1910.1200
Tuberculosis and Respiratory Protection. 1910.134, 1910.134(f)(2), 1910.134(f)(3)
Clarification of OSHA's asbestos standards for general industry and construction and the respiratory protection standard as applied to medical surveillance of employees. 1910.134, 1910.1001, 1910.1001(g), 1910.1001(g)(1), 1910.1001(l), 1926.1101, 1926.1101(h), 1926.1101(h)(1), 1926.1101(h)(2), 1926.1101(h)(2)(ii), 1926.1101(l)(4), 1926.1101(m)(1)(i)
OSHA training Standards Policy Statement. 1910.134(k)(5)(ii), 1910.147(c)(7)(i), 1910.1030(g)(2)(vii)(N), 1926.21(b)(2)
Performance of user seal checks and whether positive and/or negative seal checks are required when donning a respirator. 1910.134, 1910.134 App B-1
Clarification of OSHA's requirement for breathing air to have at least 19.5 percent oxygen content. 1910.134, 1910.134(d)(2)(i)(A), 1910.134(d)(2)(i)(B), 1910.134(d)(2)(iii)
PSM compliance for ammonia refrigeration systems. 1910.38, 1910.119, 1910.119(d)(3)(i), 1910.119(d)(3)(ii), 1910.119(e)(3), 1910.119(j)(6)(i), 1910.119(j)(6)(ii), 1910.119(k)(2), 1910.119(l)(2)(i), 1910.119(l)(4), 1910.119(l)(5), 1910.119(m)(3), 1910.119(o)(1), 1910.120, 1910.134, 1910.147, 1910.147(c)(4)(ii)
Tuberculosis and Respiratory Protection: prohibition on enforcement of annual fit testing requirements during fiscal year 2006. 1910.134, 1910.134(f)(2), 1910.134(f)(3)