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.

February 28, 1997

MEMORANDUM FOR:     PATRICIA CLARK
                   Regional Administrator

FROM:               JOHN B. MILES, JR., Director
                   Directorate of Compliance Programs Assistance

SUBJECT:            Akzo-Nobel Chemicals - Limits of a Process

The Region II - Office of Solicitor is currently considering a case involving Akzo-Nobel Chemicals. The Region II Office of the Solicitor through the National Office of the Solicitor, has requested from this office an interpretation of OSHA's 29 CFR 1910.119 (Process Safety Management [PSM] of Highly Hazardous Chemicals [HHC]; Explosives and Blasting Agents) standard. Specifically, they have requested an interpretation on the issue of the extent of the limits or boundaries of a covered process.

In this case, the company does not dispute it has a covered process, as defined by 29 CFR 1910.119. However, what is disputed is the limits or the boundaries of the process downstream from the equipment the company stipulates is part of the covered process. The company contends that interconnected equipment downstream from what it stipulates as the covered process should not be included in the boundaries of the covered process. The company contends there is no circumstance, i.e. deviations, upsets, releases, etc., which might occur downstream (outside) from the stipulated covered process, which could affect a catastrophic release of HHC in the upstream stipulated covered process. Therefore, the company contends that since there is no potential for a catastrophic release of a HHC, those downstream aspects should be considered as being outside the limits or boundaries and should not be considered as part of the covered process.

It is OSHA's position that this issue can be resolved through the following analysis: Employers must determine:

1) the extent of process(es) by utilizing the definition of process [1910.119(b)] which includes any vessels which are connected and separate vessels located such that a HHC could be involved in a potential release. Engineering and administrative controls required by the PSM standard to prevent catastrophic release of a covered HHC may not be used to determine the extent of a process as defined in paragraph 1910.119(b). This interpretation is predicated on the assumption that an event such as an explosion will take place in the process notwithstanding such controls;

2) determine whether the process contains at any particular time a threshold quantity (TQ) or greater amount of a PSM HHC. If so, the process is covered by the PSM standard; and

3) consider each aspect of the process as defined to determine the extent of PSM coverage for each particular aspect. Aspects of the process which contain a HHC would be covered by all PSM elements, such as information, process hazard analysis and mechanical integrity. Aspects which do not contain HHC, but are interconnected or located nearby are part of the process. Such aspects may or may not be covered by the PSM standard based on whether the particular aspects could cause a HHC release or interfere with mitigating the consequences if there was a HHC release. If the particular aspects do not contain a HHC but could cause a HHC release or interfere with mitigating the consequences of a HHC release, then based on the employers analysis, various elements of PSM would apply to these aspects;

If based on this analysis, it is determined that interconnected equipment downstream from the stipulated covered process cannot cause a HHC release or interfere with the mitigation of the consequences of a HHC release, and the equipment does not itself contain a TQ or greater amount of a HHC, then such equipment could safely be considered outside the limits or boundaries of the covered process.

OSHA intends that the PHA be an objective verification to ensure that the process, as determined by the employer (using steps including #l through #3 above) is managed in accordance with the requirements of the PSM Standard.

Paragraph 1910.119(l) process safety management of changes are anticipated over the service life of the process. Aspects of the process impacted by a change must be reevaluated to determine the extent to which they are covered by the PSM standard. Of concern is that aspects could be removed from further consideration by an earlier evaluation of the process if the extent of the process was determined other than described above. As a consequence of a change, an overlooked aspect could contribute to the cause of a catastrophic release or interfere with mitigating the consequences if there was a HHC release.

The determination as to whether Akzo-Nobel Chemical's equipment which is interconnected and downstream from what they stipulate to be a covered process would be based on the analysis process delineated above.

If you have any questions contact Ron Davies (202)219-8031 or Mike Marshall (202)219-8118 ext. 12, of my staff.