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
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)
Requirement for flame-resistant clothing in petrochemical plant covered by PSM. 1910.132, 1910.132(a), 1910.119, 1910.119(f)(1)(iii)(B), 1910.119(h)(2), 1910.119(h)(3), 1910.119(j)(2)
Clarification of the retail facilities exemption under the PSM standard. 1910.119, 1910.119(a)(2)(i)
Use of ANSI/ISA S84.00.01-2004 Parts 1-3 (IEC 61511 MOD) to comply with OSHA's Process Safety Management standard 1910.119
Requirements for the control of personnel entering a facility under the Process Safety Management standard. 1910.119(f)(4), 1910.119(h)(2)(iv), 1910.119(n)
Evaluation of scenarios regarding PSM requirements related to normally unoccupied remote facilities and natural gas processing plants (gas plant). 1910.119, 1910.119(b)
Documentation methods used to comply with the qualitative evaluation of a range of possible safety/health effects of "failure of controls" requirement of the PSM standard. 1910.119, 1910.119(e), 1910.119(e)(3)
Process safety information for ventilation system design. 1910.119, 1910.119(d)(3)(i), 1926.64(d)(3)(i)
Requirements for emergency response and planning under the Process Safety Management Standard. 1910.38(a), 1910.38(c)(3), 1910.119(n), 1910.120(a), 1910.120(q), 1910.120(q)(1), 1910.120(q)(6)(ii), 1910.120(q)(6)(iii)
OSHA enforcement policy of the PSM standard distilleries and related facilities in SIC 2085. 1910.119, 1910.106, 1910.119(a)(1)(ii)(B), 1926.64(a)(1)(ii)(B)
Clarification of PSM applicability to processes that are based partly or solely on quantities in connected atmospheric storage tanks. 1910.119, 1910.119(a)(1)(ii)(B), 1910.1450
PSM applicability to warehousing flammable liquids and other HHCs. 1910.119, 1910.119(a)(1)(ii)(B), 1910.119(b), 1910.119(o)
Process hazard analysis facilitator's training requirements. 1910.119(e)(4)
Determination of safety for existing process equipment is required prior to start-up. 1910.119(d)(3)(iii)
Retailer exemption from the PSM standard for anhydrous ammonia dealers. 1910.119(a)(2)(i)
Thomas' MAPP gas glass mold heat processes fall within the PSM hydrocarbon fuels exemption. 1910.119(a)(1)(ii)(A)
Applicability of PSM standard to on-site use of methane as fuel. 1910.119(a)(1), 1910.119(h)(3), 1926.64(a)(1), 1926.64(h)(3)
OSHA will not enforce the PSM standard at oil and gas production facilities. 1910.119(a)
Compliance with PSM and ANSI/ISA-S84.01 for safety instrumented systems 1910.119(d)(3), 1910.119(f)(1)(iv), 1910.119(j)
Process Safety Management (PSM) applicability to liquid petroleum gas (LPG) bottle filling process. 1910.119(a)