The U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) has issued its official interpretation and explanation of the phrase "on site in one location" in the "Application" section of OSHA's Process Safety Management (PSM) of Highly Hazardous Chemicals standard. The interpretation was published in the June 7 Federal Register.

"This official interpretation should help provide additional clarity to an earlier Notice of Proposed Rulemaking on the threshold quantities of highly hazardous chemicals," said Assistant Secretary of Labor for OSHA Edwin G. Foulke Jr. "This interpretation has been accepted by our stakeholders and should further aid those who are affected by the PSM standard."

OSHA interprets "on site in one location" to mean that the standard applies when a threshold quantity of a highly hazardous chemical (HHC) exists within an area under the control of an employer or group of affiliated employers. It also applies to any group of vessels that are interconnected, or in separate vessels that are close enough in proximity that the HHC could be involved in a potential catastrophic release.

The meaning of "on site in one location" was at issue in a recent case before the Occupational Safety and Health Review Commission. In that decision, the Review Commission asked whether that language was meant to limit, in some way, the applicability of the standard to a highly-hazardous chemical process. The Review Commission decided it could not determine whether the cited activities were both "on site" and "in one location," and requested that OSHA clarify its interpretation.