Lockout/Tagout — The Control of Hazardous Energy

OSHA's Control of Hazardous Energy standard (29 CFR 1910.147) is one of the most frequently cited general industry standards. It protects workers who service, maintain, or repair machines and equipment from the unexpected release of hazardous energy. Every year, LOTO-related incidents kill approximately 120 workers and injure nearly 50,000. Hazardous energy types covered: electrical, mechanical, hydraulic, pneumatic, chemical, thermal (heat and cold), and gravitational (components held up by springs, gravity, or other means). All forms must be identified and controlled.

The LOTO procedure has six essential steps: (1) Prepare — identify the equipment to be serviced, all energy sources, and the type and magnitude of each; (2) Shut down — notify affected employees and shut down the equipment using normal stopping procedure; (3) Isolate — physically isolate all energy sources by opening disconnects, closing valves, or otherwise blocking energy flow; (4) Apply LOTO devices — place each authorized employee's lock and tag on every energy isolation point; (5) Release stored energy — bleed hydraulic lines, discharge capacitors, restrain springs, lower suspended components, or otherwise neutralize all stored/residual energy; (6) Verify — attempt to start the equipment (confirm it doesn't start) and use a meter or test light to verify de-energization. To restore energy after maintenance: verify work is complete, remove all tools, ensure all workers are clear, remove LOTO devices (only the person who applied them), notify affected employees, and restore energy.

LOTO hardware: locks must be individually keyed (no master key that could be used without the authorized employee's knowledge), tags must identify the employee, and lockout hasps allow multiple workers to apply their own locks for group LOTO situations. LOTO devices must be used only for LOTO — not for securing tool boxes or other purposes. LOTO must be performed before any maintenance, repair, or service that could expose workers to hazardous energy — even 'quick' jobs like clearing a jam or changing a belt. LOTO audits must be conducted at least annually to verify the procedure is being followed correctly.