1. n. 
Abbreviation for Occupational Safety and Health Act of the US. OSHA laws protect safety and health of workers and give workers the right to know what materials they are handling. Safe handling of mud chemicals and the general safety of all drilling operations are of prime concern to OSHA, the operator and the mud engineer. Monitoring for toxic hydrogen sulfide [H2S] in air around the rig and testing mud for sulfides are an essential part of rig safety.