Oil and gas extraction, and associated servicing activities involve many types of equipment and materials. Identifying and controlling hazards is critical to preventing injuries and deaths (US Department of Labor, no date).
Alternative definition: For the purpose of the C155 - Occupational Safety and Health Convention, 1981 (No. 155) (ILO, 1981):
a) the term branches of economic activity covers all branches in which workers are employed, including the public service.
b) the term workers covers all employed persons, including public employees.