After an armed guard employed by Schaad Detective Agency, Inc., was shot and killed during an attempted robbery on the Pennsylvania Turnpike, the Occupational Safety and Health Administration issued the company a serious citation alleging a violation of the personal protective equipment (PPE) standard, 29 C.F.R. § 1910.132(a). The Secretary alleges that Schaad violated the standard by failing to ensure that its armed guards assigned to provide security for the turnpike’s fare collection operation wore bulletproof vests. Following a hearing, Administrative Law Judge Dennis L. Phillips vacated the citation, concluding that the cited provision does not apply. We agree that § 1910.132(a) does not apply—albeit for different reasons than those of the judge—and so we also vacate the citation.