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. This 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. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

March 23, 2000

Ms. Lois M. Ferson
Manager of Standards Services
67 Alexandria Drive
P.O. Box 12277
Research Triangle Park, NC 27709

Dear Ms. Ferson:

Thank you for your November 9, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You have questions regarding OSHA's Process Safety Management of Highly Hazardous Chemicals; Explosives and Blasting Agents Standard (PSM), 29 CFR 1910.119. You have specific questions regarding the application of the PSM standard to a national consensus standard for safety instrumented systems. We apologize for the delay in our response.

Question 1: Does the modification of corporate standards to comply with ANSI/ISA-S84.01 ensure compliance with related areas of 29 CFR 1910.119?

Response: The American National Standards Institute (ANSI)/International Society for Measurement and Control (ISA) document Application of Safety Instrumented Systems for the Process Industries, ANSI/ISA-S84.01-1996 (S84.01), is a national consensus standard for the application of safety instrumented systems (SIS) for the process industries. The SIS addressed in S84.01 include electrical, electronic and programmable electronic technology. The objective of S84.01 is to define the requirements for SIS. Standard S84.01 provides information related to the design and manufacture of SIS products, selection, application, installation, commissioning, pre-startup acceptance test, operation, maintenance, documentation and testing.

It is important to note that one of the "exclusions" contained in S84.01, Section 1.2, does not define when SIS are required. As with any process equipment, the employer is responsible for any SIS that are utilized at a facility covered by the OSH Act. The employer's responsibility would include determining if SIS are needed to control hazards of a process.

The PSM standard contains a number of requirements for equipment associated with a covered process, including SIS. The PSM standard [1910.119(d)(3)] requires an employer to document information pertaining to equipment in the process, this equipment includes SIS when utilized. Specifically: 1) 1910.119(d)(3)(i)(F) requires an employer to document which design codes and standards are used for SIS; and 2) 1910.119(d)(3)(ii) requires an employer to document that SIS comply with recognized and generally accepted good engineering practices.

As S84.01 is a national consensus standard, OSHA considers it to be a recognized and generally accepted good engineering practice for SIS. As per the Operating procedures requirement of PSM, [1910.119(f)(1)(iv)], the employer is required to develop and implement written operating procedures for safely conducting activities involving safety systems and their functions. Further, the Mechanical integrity element of PSM covers SIS under 1910.119(j)(1)(iv) and 1910.119(j)(1)(v). The employer is required by 1910.119(j)(4) to conduct inspection and testing on process equipment, including SIS, as per recognized and generally accepted good engineering practices. If an employer documents per 1910.119(d)(3)(i)(F) that it will comply with S84.01 for SIS and it meets all S84.01 and other OSHA PSM requirements related to SIS, the employer will be considered in compliance with OSHA PSM requirements for SIS.

Question 2: We are interested if your agency views ANSI/ISA-S84.01 as the benchmark OSHA will use to measure compliance with 29 CFR 1910.119?

Response: The PSM standard is a performance-oriented standard. When not specified, the employer has flexibility in complying with the requirements of PSM, including recognized and generally accepted good engineering practices. With respect to SIS, OSHA does not specify or benchmark S84.01 as the only recognized and generally accepted good engineering practice. Based on input from stakeholders, OSHA stated in the PSM final rule (see F.R., Volume 57, No. 36, pg 6390) that it did not intend to incorporate by reference into PSM all the codes and standards published by consensus groups. Therefore, in evaluating whether an employer's engineering practices with respect to SIS complies with PSM, OSHA would consider among other factors, whether the employer meets the requirements of S84.01. See OSHA's website [(www.osha.gov) for a letter dated
December 7, 1995 to Mr. J.B. Evans, Union Carbide] for a similar discussion on another ISA document, ISA S91.01 ANSI/ISA-S91.01-1995 - Identification of Emergency Shutdown Systems and Controls that are Critical to Maintaining Safety in Process Industries.

The previous discussion has focused on the relationship of S84.01 to PSM. It is also important to note that there are a large percentage of processes which are not covered by PSM which may include SIS covered by S84.01. The employer may be in violation of the General Duty Clause, Section 5(a)(1) of the OSH Act, if SIS are utilized which do not conform with S84.01 and hazards exist related to the SIS which could seriously harm employees.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Such guidance could also be affected by subsequent rulemaking. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's web-site at
http://www.osha.gov. If you have any further questions, please feel free to contact the [Office of General Industry Enforcement] at (202) 693-1850.



Richard E. Fairfax, Director
[Directorate of Enforcement Programs]

[Corrected 6/2/2005]