Congress passed the Occupational Safety and Health Act of 1970 ("OSH Act" or "act") to "assure so far as possible every working man and woman in the Nation safe and healthful working conditions and to preserve our human resources …" In the years leading up to the OSH Act, approximately 14,500 workers died annually from work-related injuries, and the number of Americans dying from work-related injuries between 1966 and 1970 exceeded the number of Americans killed in the Vietnam War during that period. Additionally, work-related injuries disabled approximately 2.2 million Americans each year. Congress therefore found existing health and safety standards inadequate at protecting workers and passed the OSH Act, whereby it sought a "comprehensive, nationwide approach" to occupational health and safety. The OSH Act obligated the Secretary of Labor to protect occupational safety and health as required by the act. However, the act also created the Assistant Secretary of Labor for Occupational Safety and Health, and thus the Occupational Safety and Health Administration ("OSHA"), to whom the Secretary of Labor has delegated responsibility for his obligations under the act. The OSH Act also created the Occupational Safety and Health Review Commission ("OSHRC") —an adjudicatory agency that is independent of the Department of Labor and therefore OSHA—that is tasked with reviewing OSHA enforcement actions (i.e., citations and penalties). The OSH Act contains express limitations on its applicability. For example, Section 4(b)(1) of the act provides that the act does not apply "to working conditions of employees with respect to which other federal agencies … exercise statutory authority" over occupational safety and health regulations and standards. Congress apparently intended this language to prevent regulatory inefficiency by precluding OSHA from duplicating worker safety efforts in areas already regulated by other agencies. To that end, health and safety regulations of other agencies that apply to a workplace hazard preempt OSHA's regulations regarding that hazard. The OSH Act further expressly limits its applicability by allowing states to control occupational safety and health regulation through state plans. If OSHA approves of a state plan, which requires, among other things, that the plan provide health and safety protection that is at least as adequate as the protections provided by OSHA, then the state plan requirements, and not OSHA's standards and regulations, will apply. Finally, the OSH Act applies only to employment performed in U.S. states and territories, generally does not apply to federal, state, or local government employment, and only applies to employers with employees (i.e., it does not apply to self-employed people). The OSH Act contains two primary enforcement provisions, each of which furnishes a unique obligation upon employers. First, Section 5(a)(1) of the act, the so-called "General Duty Clause," requires all employers, regardless of industry, to provide workplaces that are free of potentially harmful hazards. Second, the act mandates employer compliance with OSHA's workplace safety standards, some of which are industry specific. The General Duty Clause and OSHA's workplace safety standards are treated the same for purposes of complaints, inspections, and citations. That is, employers are equally bound to comply with the General Duty Clause and applicable OSHA standards and both are similarly enforced through complaints, inspections, and citations. OSHA bears the burden of showing that an employer has violated the General Duty Clause or an OSHA standard by a preponderance of the evidence. Additionally, employers cannot be held liable for violations of the General Duty Clause or an OSHA standard unless they had actual or constructive knowledge of the violation's existence. Thus, after establishing that an employer has violated the General Duty Clause or an OSHA standard by a preponderance of the evidence, OSHA bears the added burden of proving that the employer did so with actual or constructive knowledge. Under the General Duty Clause, employers must provide employees with "employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm." Apparently recognizing the impracticality of having OSHA issue safety standards for every type of employer and employment, Congress intended the General Duty Clause to be a catchall provision establishing a broad employer duty to protect worker health and safety in the absence of applicable OSHA-created standards. To that end, when an OSHA-created standard applies to a hazard, an employer's compliance with the standard can be deemed to satisfy, and thereby preempt, the General Duty Clause. However, this preemption occurs only when the employer successfully proves, as an affirmative defense, that the OSHA standard adequately addresses the hazard or, if the standard inadequately addresses the hazard, that the employer did not know of the inadequacy of the standard. Thus, if an employer knows that a safety standard inadequately protects employees against a hazard, the employer must still comply with the General Duty Clause regarding that hazard. To successfully prove a violation of the General Duty Clause, OSHA must show that (1) a workplace condition poses a hazard to an employee; (2) the employer constructively or actually recognizes that the workplace condition is a hazard; (3) the hazard is causing, or is likely to cause, serious physical harm or death; and (4) feasible means exist to materially reduce or eliminate the hazard. If OSHA successfully proves a violation of the General Duty Clause, it must then show that the employer violated the clause with actual or constructive knowledge for the employer to have violated the OSH Act. A General Duty Clause violation requires that a workplace condition pose a hazard to an employee. This does not require actual harm to an employee; the ability of a workplace condition to harm an employee can render it a hazard. Additionally, OSHRC has recognized that a workplace condition can be a hazard absent a significant chance that the condition will injure an employee. On the other hand, for a condition to be a hazard, it must occur in "other than a freakish or utterly implausible concurrence of circumstances." Accordingly, for a workplace condition to be a hazard, it must be more than "utterly implausible" that the condition will injure or kill an employee, but there need not be a significant chance that it will injure or kill an employee. If a workplace condition is a hazard, OSHA must establish that it is a "recognized" hazard to prove a violation of the General Duty Clause. A recognized hazard is a workplace condition that is either recognized as hazardous by the employer's industry, or that the employer actually knows to be hazardous. In determining that an industry recognizes a hazard, OSHRC has found persuasive evidence showing that, for example, accepted industry standards or industry publications acknowledge the hazard. Similarly, OSHA can establish an employer's actual knowledge of a hazardous condition by putting forth various types of evidence, including evidence showing that there were numerous previous accidents or injuries or employee complaints. An employer's actual knowledge of a hazardous condition can sustain a General Duty Clause violation even if the employer's industry has not recognized the condition as hazardous. If OSHA successfully establishes that a workplace condition is a recognized hazard, it must prove that the hazard is causing, or is likely to cause, serious physical injury or death to an employee. OSHRC has held that the probability that physical harm or death will occur, which it considers when determining whether a hazard exists as discussed above, is irrelevant in determining whether a recognized hazard is causing, or is likely to cause, serious physical harm or death to employees. Rather, OSHRC considers the level of physical harm that an employee would face if an accident were to happen, no matter how slight the chance an accident would happen in the first place. For example, in Waldon Health Care Center , a hazardous workplace condition presented only a small chance that employees would catch Hepatitis B, a virus from which, OSHRC noted, most people fully recover. Even so, OSHRC found serious physical harm or death likely because a small percentage of people that catch Hepatitis B die or do not fully recover from it, and the hazardous condition therefore had the chance, though apparently slight, of seriously injuring or killing employees. Previous incidents wherein the recognized hazard caused serious physical harm or death are not necessary to establish that the hazard is causing, or is likely to cause, injury or death. However, it appears that previous injuries or deaths are sufficient , unless rebutted, to establish that the hazard is causing, or is likely to cause, serious physical injury or death. Reviewing courts generally defer to OSHRC determinations that a recognized hazard is likely to cause serious injury or death. Courts and the OSHRC generally agree that Congress did not intend the General Duty Clause to protect employees against all conceivable workplace hazards. Rather, Congress intended the clause to protect employees against only hazards that are preventable . Accordingly, if OSHA successfully establishes that a workplace condition poses a recognized hazard that is likely to cause serious physical harm or death to an employee, OSHA must then prove that the hazard is preventable; that is, feasible means of materially reducing the hazard exist. In practice, litigation of whether feasible means of reducing a recognized hazard exist appears to unfold in two steps. First, because OSHA bears the burden of establishing that a feasible means of abatement exists, OSHA must initially show that an employer could feasibly take specific actions that would materially reduce a risk to employees. Next, the employer often responds by arguing that OSHA's suggested actions are infeasible. OSHA bears the burden of showing that a feasible means of materially reducing a hazard exists, which requires it to show that specific abatement actions by an employer would feasibly and materially reduce the hazard. These abatement actions generally appear to fall into two categories: physical means of abatement and abatement by implementing new or additional procedures. When proposing an abatement action, OSHA can show its feasibility through evidence showing, for example, that similar employers in the industry have successfully implemented the means of abatement or industry standards recommend the means of abatement.