The Act can be found in the United States Code at title 29, chapter 15.
The first federal safety legislation was enacted in the Progressive period. In 1893, Congress passed the Safety Appliance Act, the first federal statute to require safety equipment in the workplace (the law applied only to railroad equipment, however). In 1910, in response to a series of highly-publicized and deadly mine explosions and collapses, Congress established the federal Bureau of Mines to conduct research into mine safety (although the Bureau had no authority to regulate mine safety). Backed by trade unions, many states also enacted workers' compensation laws which discouraged employers from permitting unsafe workplaces. These laws, as well as the growing power of labor unions and public anger toward poor workplace safety, led to significant reductions in worker accidents for a time.
Industrial production increased significantly in the United States during World War II, and industrial accidents soared. Winning the war took precedence over safety, and most labor unions were more concerned with maintaining wages in the face of severe inflation than with workplace health and safety. After the war ended, however, workplace accident rates remained high and began to rise. In the two years preceding OSHA's enactment, 14,000 workers died each year from workplace hazards, and another 2 million were disabled or harmed. Additionally, the "chemical revolution" introduced a vast array of new chemical compounds to the manufacturing environment. The health effects of these chemicals were poorly understood, and workers received few protections against prolonged or high levels of exposure. While a few states, such as California and New York, had enacted workplace safety as well as workplace health legislation, most states had not changed their workplace protection laws since the turn of the century.
On April 14, 1969, President Richard Nixon introduced two bills into Congress which would have also protected worker health and safety. The Nixon legislation was much less prescriptive than the Johnson bill, and workplace health and safety regulation would be advisory rather than mandatory. However, Representative James G. O'Hara and Senator Harrison A. Williams introduced a much stricter bill similar to the Johnson legislation of the year before. Companion legislation introduced in the House also imposed an all-purpose "general duty" clause on the enforcing agency as well. With the stricter approach of the Democratic bill apparently favored by a majority of both chambers, and unions now strongly supporting a bill, Republicans introduced a new, competing bill. The compromise bill established the independent research and standard-setting board favored by Nixon, while creating a new enforcement agency. The compromise bill also gave the Department of Labor the power to litigate on the enforcement agency's behalf (as in the Democratic bill). In November 1970, both chambers acted: The House passed the Republican compromise bill, while the Senate passed the stricter Democratic bill (which now included the general duty clause). A conference committee considered the final bill in early December 1970. Union leaders pressured members of the conference committee to place the standard-setting function in the Department of Labor rather than an independent board. In return, unions agreed to let an independent review commission have veto power over enforcement actions. Unions also agreed to removal of a provision in the legislation which would have let the Secretary of Labor shut down plants or stop manufacturing procedures which put workers in "imminent danger" of harm. In exchange for a Republican proposal to establish an independent occupational health and safety research agency, Democrats won inclusion of the "general duty" clause and the right for union representatives to accompany a federal inspector during inspections. The conference committee bill passed both chambers on December 17, 1970, and President Nixon signed the bill on December 20, 1970.
Act also established the National Institute of Occupational Safety and Health (NIOSH), an independent research institute in the then-Centers for Disease Control.
The Act defines an employer to be any \"person engaged in a business affecting commerce who has employees, but does not include the United States or any state or political subdivision of a State.\" The Act applies to employers as diverse as manufacturers, construction companies, law firms, hospitals, charities, labor unions and private schools. Churches and other religious organizations are covered if they employ workers for secular purposes. The Act excludes the self-employed, family farms, workplaces covered by other federal laws (such as mining, nuclear weapons manufacture, railroads and airlines) and state and local governments (unless state law permits otherwise). The Act does cover federal agencies, as well as the United States Postal Service.
Section 5 of the Act contains the "general duty clause." The "general duty clause" requires employers to 1) Maintain conditions or adopt practices reasonably necessary and appropriate to protect workers on the job; 2) Be familiar with and comply with standards applicable to their establishments; and 3) Ensure that employees have and use personal protective equipment when required for safety and health. OSHA has established regulations for when it may act under the "general duty clause." The four criteria are: 1) There must be a hazard; 2) The hazard must be a recognized hazard (e.g., the employer knew or should have known about the hazard, the hazard is obvious, or the hazard is a recognized one within the industry); 3) The hazard could cause or is likely to cause serious harm or death; and 4) The hazard must be correctable (OSHA recognizes not all hazards are correctable). Although theoretically a powerful tool against workplace hazards, it is difficult to meet all four criteria. Therefore, OSHA has engaged in extensive regulatory rule-making to meet its obligations under the law.
Due to the difficulty of the rule-making process (which is governed by the Administrative Procedures Act), OSHA has focused on basic mechanical and chemical hazards rather than procedures. Major areas which its standards currently cover are: Toxic substances, harmful physical agents, electrical hazards, fall hazards, hazards associated with trenches and digging, hazardous waste, infectious disease, fire and explosion dangers, dangerous atmospheres, machine hazards, and confined spaces.
Section 8 of the Act covers reporting requirements. All employers must report to OSHA within eight hours if an employee dies from a work-related incident, or three or more employees are hospitalized as a result of a work-related incident. Additionally, all fatal on-the-job heart attacks must also be reported. Section 8 permits OSHA inspectors to enter, inspect and investigate, during regular working hours, any workplace covered by the Act. Employers must also communicate with employees about hazards in the workplace. By regulation, OSHA requires that employers keep a record of every non-consumer chemical product used in the workplace. Detailed technical bulletins called material safety data sheets (MSDSs) must be posted and available for employees to read and use to avoid chemical hazards. OSHA also requires employers to report on every injury or job-related illness requiring medical treatment (other than first aid) on OSHA Form 300, "Log of Work-Related Injuries and Illnesses" (known as an "OSHA Log" or "Form 300"). An annual summary is also required and must be posted for three months, and records must be kept for at least five years.
Section 11(c) of the Act prohibits any employer from discharging, retaliating or discriminating against any employee because the worker has exercised rights under the Act. These rights include complaining to OSHA and seeking an OSHA inspection, participating in an OSHA inspection, and participating or testifying in any proceeding related to an OSHA inspection.
Section 18 of the Act permits and encourages states to adopt their own occupational safety and health plans, so long as the state standards and enforcement "are or will be at least as effective in providing safe and healthful employment" as the federal OSH Act. States which have such plans are known as "OSHA States." As of 2007, 22 states and territories operated complete plans and four others had plans which covered only the public sector.