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 OSHA standards when an employer is using the "Focused Electrode Leak Locator" (FELL) 1910.302, 1910.303, 1910.307(c)(1), 1910.307(c)(2), 1910.307(c)(3), 1910.399, 1910.146
Application of 29 CFR 1910 Subpart S to design of industrial machinery 1910 Subpart S, 1910.303(a), 1910.399
NRTL requirements for shielding gas regulators. 1910 Subpart S, 1910.303(a), 1910.399, 1910 Subpart Q, 1910.251, 1910.253
Approval of employee-furnished equipment for use in hazardous locations; definition of "electric utilization equipment." 1910.303, 1910.303(b)(1), 1910.399
Acceptability of using a light switch as a disconnecting means for the electrical lockout/tagout standard. 1910.303(b)(2), 1910.333(a)(2), 1910.333(b)(1), 1910.333(b)(2), 1910.399
The definition of "Readily accessible" does not necessarily preclude the locking of electrical panels, provided those needing ready access are provided a key or lock combination. 1910.399
Approval requirements for replacement, modification, repair, or rehabilitation of electrical utilization equipment. 1910.7, 1910.302(b)(2), 1910.303(a), 1910.399
Use of personal cooling fans listed for "residential use only" in an industrial setting. 1910.303, 1910.303(b)(2), 1910.399
Use of temporary panelboard ingress barriers in General Industry settings. 1910.303, 1910.303(a), 1910.399
Electrical equipment approved by a NRTL is acceptable to OSHA. 1910.7, 1910.303(a), 1910.303(b), 1910.399
Acceptability of locking switches in the closed (on) position for transformers attached to the main bus duct system. 1910.304(d)(1), 1910.399
Fixed Wiring in Research Facilities and High Voltage Cable Tray Systems at Department of Energy (DOE) Research Laboratories 1910.305(a), 1910.305(a)(2), 1910.305(a)(2)(iii)(B), 1910.305(a)(3), 1910.305(b), 1910.305(g)(1), 1910.305(g)(1)(i), 1910.305(g)(1)(iii), 1910.399
Electrical equipment grounding requirements on concrete floors. 1910.304, 1910.304(f)(5)(v)(C)(5), 1910.303(g)(1), 1910.399
Installation and use of electrical equipment must be consistent with NRTL intructions for that equipment. 1910.303(b)(2), 1910.399
Use of portable vacuum cleaners for cleaning up aluminum and wood dust. 1910.399, 1910.307, 1910.307(b)(2)
Acceptability of modifying a standard on/off switch to provide lockout capability to a machine. 1910.147, 1910.147(c)(3), 1910.147(c)(2)(iii), 1910.303(a), 1910.399, 1910.303
Electrical safety requirements for rechargeable racks for paging transmitters. 1910.305(j)(3), 1910.399
Applicable OSHA standards and safety considerations for microwave device use in a laboratory 1910.1450, 1910.1450(e)(3)(vii), 1910.97, 1910.303(b)(2), 1910.399, 1910.106, 1910.1000
Review of electrical schematic diagrams; OSHA does not approve equipment designs. 1910.399(a), 1910.304(f)(3)(i)
Applicability of OSHA's LOTO standards; isolation and verification procedures. 1910.147, 1910.333(b), 1910.399