Lockout tagout, or LOTO, is a set of procedures that keeps a machine from starting up or releasing stored energy while someone services it. In the US, OSHA's standard 29 CFR 1910.147 requires a written energy control program, worker training and periodic inspections for covered general industry work.
What hazardous energy means
OSHA treats electrical, mechanical, hydraulic, pneumatic, chemical, thermal and other energy as hazardous when it can injure a worker. The agency's own examples are a steam valve opening during a pipe repair, a jammed conveyor releasing onto a worker, and internal wiring shorting during equipment repair. Harm named includes electrocution, burns, crushing, cuts, amputations and fractures.
Stored energy counts. A machine that is switched off can still hold pressure, a raised load or a charged capacitor.
When the rule applies
The standard covers servicing and maintenance: constructing, installing, setting up, adjusting, inspecting, modifying, lubricating, cleaning, unjamming and tool changes, where unexpected energization or release is possible.
It does not cover everything. Exclusions include construction and agriculture, and electric utility installations under exclusive utility control, where other standards apply. Normal production work is outside it unless the worker has to remove or bypass a guard or put a body part into a danger zone. Check the current text for your own situation.
The three parts of the program
Procedures. They must be written down and cover how the equipment is shut down and isolated, how devices are placed, removed and transferred, and how the isolation is tested to confirm it worked. A narrow exception to documentation exists, but only when a list of conditions is all met, including a single identifiable energy source.
Training. Authorized employees learn to recognise energy sources and isolate them. Affected employees learn the purpose of the procedure. Everyone else nearby learns not to restart locked or tagged equipment. Retraining is required after changes in job, equipment or procedure, or when inspection finds gaps.
Inspection. At least once a year, someone who does not use the procedure checks that it is followed, and the employer certifies it.
Hardware and who is who
Employers supply the locks, tags and related hardware. Devices must be standardised in the facility by colour, shape or size, show who applied them, and be used for nothing else. An authorized employee locks or tags out equipment to service it. An affected employee uses the machine or works nearby.
Why software teams care
Many modern machines are controlled by PLCs and remote interfaces. A remote start command or a scheduled job can re-energize equipment in a way a padlock on a breaker would not. A procedure that only considers the local disconnect misses that path. Our post on interlocks and bypass risk covers how control logic fits with physical isolation.
Quick check
Is a push button stop an energy isolating device?
No. OSHA's definition says push buttons and control circuit selector switches do not qualify. A breaker, disconnect switch or line valve that physically blocks energy does.
Is LOTO a cybersecurity topic?
It is a safety procedure, but remote access and automated starts are a reason to review it with your controls and IT teams.
Sources
This is general information, not legal advice. Check the current standard.
Last reviewed: 19 October 2026.
