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Standard Interpretations
12/22/2003 - Process safety information for ventilation system design.
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• Standard Number: 1910.119; 1910.119(d)(3)(i); 1926.64(d)(3)(i)

December 22, 2003

Mr. Stephen Barker
Senior Engineer
Williams
One Williams Center
Post Office Box 21628
Tulsa, OK 74121

Dear Mr. Barker:

Thank you for your October 16, 2002 letter to the Occupational Safety and Health Administration (OSHA) regarding the documentation requirement under OSHA's Process Safety Management (PSM) standard at 29 CFR 1910.119. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in responding to your inquiry.

Background: You requested clarification of the documentation requirements for "Ventilation system design," described under 29 CFR 1910.119(d)(3)(i)(E), at these facilities: 1) natural gas compression and/or processing facilities; 2) anhydrous ammonia terminals including pressure vessel storage; 3) natural gas liquid (NGL) terminals including pressure vessel storage; and 4) gasoline/diesel terminals, including tank storage.

Scenario: You included the following proposals to meet the requirements:

  1. Where ventilation is used to declassify or alter the Electrical Area Classification (EAC) of a building, the company EAC standard (currently API 500) should be documented as the design basis of the ventilation. The documentation should include all assumptions and calculations used.


  2. Where a hydrocarbon process is housed within a building, the building should be ventilated and the design basis for the ventilation must be documented. The documentation should include what code or standard was used as the design basis as well as all assumptions and calculations. A process would include, but is not limited to pumps, piping, and/or storage of flammable liquids or NGLs. Ventilation may be mechanical or natural (vents and louvers).


  3. The code or standard must be appropriate and supportable for the process in question. Some examples are:

    1. "Structure or Building Ventilation," NFPA 58, 2001 Edition, Section 7.2.2, could be supported as appropriate for buildings at the end of the propane terminals.


    2. "Ventilation," NFPA 30, 2000 Edition, Section 5.3.4, could be supported as appropriate for buildings at most Refined Products facilities.


    3. "Building Ventilation," Williams Gas Pipelines Standard For Compressor Facility Design (FDS-1, Issue #1), Section 5.2.4, could be supported as appropriate for buildings at gathering facilities.

    EXCEPTIONS:

    1. NGL Sample Containers: So long as the total weight of NGLs stored in a building in sample containers awaiting shipment is less than 300 pounds, no ventilation requirements exist for these containers. (See NFPA 58, 2001 Edition, Section 5.3.2.1.)


    2. Refined Products Sample Bottles: So long as the total volume of Refined Products stored in a building in sample containers awaiting shipment is less than 10 gallons, no ventilation requirements exist for these containers. (See NFPA 30, 2000 Edition, Section 4.5.5.3.)

  4. Where an ammonia process is housed within a building, the building should be ventilated and the design basis for the ventilation must be documented. A process would include, but not be limited to, refrigeration, pumping, piping, and/or storage. Ventilation may be mechanical or natural (vents and louvers). The code or standard must be appropriate and supportable for the process in question. For example, the International Institute of Ammonia Refrigeration (IIAR) Bulletin 111, "Guidelines for Ammonia Machinery Room Ventilation," 1992 Edition, could be supported as appropriate for buildings housing ammonia refrigeration processes.

Question: Do the above proposals meet the 29 CFR 1910.119(d)(3)(i)(E) requirements?

Response: According to 29 CFR 1910.119(d)(3)(i)(E), employers who are covered under the PSM rule that use ventilation systems as part of their PSM programs must compile written process safety information pertaining to that equipment, including the design basis for it. Section 1910.119(d)(3)(i)(F) requires employers to document design codes or standards employed when compiling such written process safety information. (The documentation must also include all assumptions and calculations.) Therefore, industry standards such as those published by NFPA and IIAR, including NFPA 30, NFPA 58, and IIAR Bulletin 111, could serve as examples of design basis for ventilation systems, when those are designated and employed, and the documentation containing such information will meet 1910.119(d)(3)(i)(E) requirements. Such information pertaining to the equipment in the process must also include electrical classification under 1910.119(d)(3)(i)(C) and safety systems (e.g., interlocks, detection or suppression systems) under 1910.119(d)(3)(i)(H).

The industry consensus standard mentioned in your letter, API 500, does not allow reclassification of an enclosed area by means of ventilation. Section 6.3.1.2 of API 500, Second Edition, November 1997 clearly states, "Providing ventilation to allow the reclassification of an enclosed area from classified to unclassified is not allowed in enclosed areas containing devices handling hydrocarbons." Therefore, your proposal (in the scenario) which partly states, "Where ventilation is used to declassify or alter the Electrical Area Classification (EAC) of a building, the company EAC standard (currently API 500) should be documented…" is not accurate. Consequently, any documentation pertaining to such declassification will be in violation of 1910.119(d)(3)(ii).

Additionally, since we do not have information regarding Section 5.2.4 of Williams Gas Pipelines Standard For Compressor Facility Design (FDS-1, Issue #1) noted in your letter, we cannot determine whether that standard was developed based on recognized and generally accepted good engineering practices, as required under 1910.119(e)(3)(ii). If it was so developed, then it could also serve as an example as a design basis for ventilation systems at your facility.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. 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 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.

Sincerely,

Richard E. Fairfax, Director
Directorate of Enforcement Programs

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