After an employee of MasTec North America, Inc., was electrocuted while working in an aerial bucket relocating energized, overhead power lines, the Occupational Safety and Health Administration issued the company a citation alleging a serious violation of the Electric Power Transmission and Distribution standard. The cited provision requires employers to “ensure that no employee approaches or takes any conductive object closer to exposed energized parts than the employer’s established minimum approach distance, unless . . . [t]he energized part is insulated from the employee and from any other conductive object at a different potential.” 29 C.F.R. § 1926.960(c)(1)(iii)(B). Following a hearing, Administrative Law Judge Dennis L. Phillips affirmed the violation. On review, MasTec contends that the Secretary failed to establish the company’s knowledge of the violative condition. We agree and therefore vacate the citation.