In May 2017, there was a release of anhydrous ammonia on the grounds of a power plant operated by Tampa Electric Company (TECO). Subsequently, the Occupational Safety and Health Administration conducted an inspection of the worksite and issued TECO a two-item serious citation alleging violations of the Hazardous Waste Operations and Emergency Response (“HAZWOPER”) standard, 29 C.F.R. § 1910.120. Only Item 2 of that citation is at issue on review—it alleges a violation of 29 C.F.R. § 1910.120(q)(3)(iv) and proposes a $9,054 penalty, because TECO employees who responded to the ammonia release did not wear positive pressure self-contained breathing apparatus (SCBA). Following a hearing, Administrative Law Judge John B. Gatto vacated the item. For the reasons discussed below, we also vacate but on different grounds than the judge.