Eric K. Ho purchased a hospital building with the purpose of developing the building into residential housing. Ho was aware that there was asbestos at the construction site and that he was required by law to employ contractors licensed by the Texas Department of Health to handle the asbestos. Ho instead hired Manuel Escobedo and Corston Tate, neither of whom were licensed contractors, to remove the asbestos. Escobedo in turn hired 11 illegal immigrants for labor. The workers were not provided with dust masks or given training on asbestos precautions. On February 2, 1998, a city inspector issued a stop-work order due to the possibility of asbestos at the site. Ho began negotiating with a licensed contractor, Alamo Environmental (Alamo), to remove the asbestos, but ultimately never hired Alamo. Instead, Ho resumed his illegal asbestos-removal activities until March 11, 1998, when an explosion occurred after Ho had Tate illegally tap into an unmarked pipeline. The Occupational Safety and Health Administration (OSHA) investigated the site after the explosion and issued a number of violations against Ho, including violations for his failure to provide respirators to the employees and to train the employees on asbestos precautions. OSHA also charged Ho with willfully violating the Occupational Safety and Health Act (Act), 29 U.S.C. § 651 et seq., by tapping into the unmarked pipeline. Ho conceded that he had violated the respirator and training requirements, but argued that he was not subject to the Act because U.S. Secretary of Labor Elaine Chao (Secretary) had failed to demonstrate that Ho was engaged in interstate commerce. The Occupational Safety and Health Review Commission (OSHRC) found that Ho was engaged in interstate commerce and affirmed the violations. Ho and the Secretary both appealed.