Glossary · Safe work, maintenance and competence

Lockout/tagout (LOTO)

Also known as: LOTO, lockout-tagout, lockout/tagout/tryout

In machine safety, lockout/tagout (LOTO) is a procedure for isolating hazardous energy, securing the isolation devices with locks or tags, and verifying a zero-energy state before servicing or maintenance work begins. In the USA it is governed by OSHA 29 CFR 1910.147.

Machine safety
USA
Maintenance

In one sentence

Lockout/tagout (LOTO) isolates, locks and verifies hazardous energy before servicing, as required in the USA by OSHA 29 CFR 1910.147.

Example

Before replacing a die in a stamping press, the setter shuts the press down, opens and locks the main disconnect and air valve, blocks the ram, bleeds the air, and tries the start button to confirm nothing moves.

Explained in context

Context cards connect this term with others to answer one question. Also in British English and German.

How it applies

USA: 29 CFR 1910.147 requires an energy control program with written procedures, training for authorized and affected employees, and periodic inspection of the procedures at least annually. Tagout alone is allowed only where it gives protection equivalent to lockout or the device cannot be locked.
Machine safety: The typical sequence is prepare, notify, shut down, isolate, apply locks, release stored energy, verify, work, and restore with notification. Each person working applies a personal lock.
Technical documentation: Machine-specific procedures list every energy source and isolation point. The manufacturer’s instructions provide the information; the employer writes the site procedure, and both must match the machine as built.
Evidence: Periodic inspection records, training records and the procedure version in use show the program works. Having a procedure is not proof that it is followed.

Lockout/tagout vs. safety functions

An interlock, emergency stop or Safe Torque Off stops the machine through its control system. LOTO physically isolates the energy and puts it under the control of the person at risk. Only LOTO, or an alternative measure the standard permits, protects people during servicing and maintenance.