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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How to Request a Letter of Interpretation

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Date Title Standard Number
Application of the Hazard Communication standard to gray and ductile iron castings. 1910.134
Use of Chemical Cartridge Respirators for Protection Against Mercury Vapor 1910.134(d)(3)(iii)(B)(1)
Use of Bureau of Mines Approved Gas Mask Canisters 1910.134
Facial hair and respirator wearing. 1910.134
Facial hair and the wearing of respirators. 1910.134
Acceptable respirators for exposure to ethylene oxide; Acceptable respirators for exposure to ethylene oxide. 1910.134, 1910.1047
Facial hair in the face sealing area is unacceptable. 1910.134(g)(1)(i), 1910.134(g)(1)(ii), 1910.134(g)(1)(iii)
Medical Interpretation concerning exposure to H2S and respiratory protection with a perforated ear drum. 1910.134(e)
Workers cannot sign a release so they can wear a respirator with a beard. 1910.134(g)(1)(i)
Paragraph (a)(2) applies to respirators provided for emergency use. 1910.134(a)(2)
Biopacks are acceptable for fire brigade use; Biopacks are acceptable as SCBA's and may be used in IDLH atmospheres. 1910.156(f), 1910.134(c)
Negative pressure respirators unacceptable for isocyanate paints. 1910.134
Use of skin diving hood under respirator for bearded employee unacceptable. 1910.134(e)(5)(i)
Del-Monox air purifiers are unacceptable for testing carbon monoxide concentration for compressor breathing air. 1910.134(i)(7)
Cool-view welding helmets must meet Grade D breathing air requirements; Requirements for standard welding helmets. 1910.134(i)(1)(i), 1910.252(b)(2)(ii)
Carbon Monoxide Alarm/Monitoring at Abrasive Blasting Operations. 1910.94, 1910.134
Respirator air quality standards do not apply where the NRC has jurisdiction 1910.134(i)