Lockout tagout (often shortened to LOTO) is a safety procedure that ensures machines and equipment are fully shut down and unable to restart while someone is repairing or servicing them. It prevents an estimated 120 fatalities and 50,000 injuries every year in the United States. The core idea is simple: before you work on a machine, you physically disconnect its energy sources and lock those disconnection points so nobody can accidentally turn the power back on.
LOTO is required by federal workplace safety law under OSHA standard 29 CFR 1910.147, formally called the Control of Hazardous Energy standard. It applies to general industry workplaces where unexpected startup of equipment during maintenance could injure workers. Despite being well established, lockout tagout violations consistently rank among OSHA’s most cited standards. In fiscal year 2025, it was the fourth most frequently cited standard nationwide.
How Lockout Tagout Actually Works
The “lockout” part involves placing a physical lock on an energy isolating device, like a circuit breaker, disconnect switch, or line valve, so the equipment cannot be turned on. The lock can only be removed by the worker who placed it. The “tagout” part involves attaching a visible tag to that same point, warning anyone nearby that the equipment is being serviced and must not be operated.
Think of it this way: the lock physically stops someone from flipping the switch, and the tag communicates why. Both serve important but different functions. A lock provides a hard barrier. A tag provides information. OSHA strongly favors using locks whenever possible because a tag alone can be ignored or removed, while a lock cannot be overridden without the key.
The steps in a typical LOTO procedure follow a logical sequence:
- Notify affected employees that the equipment is about to be shut down for maintenance.
- Shut down the machine using its normal stopping procedure.
- Isolate all energy sources by turning off circuit breakers, closing valves, or disconnecting other supply points.
- Apply locks and tags to every energy isolation point.
- Release or restrain any stored energy that remains in the system (springs, pressurized lines, elevated parts, capacitors).
- Verify the equipment is truly de-energized by attempting to start it or testing with appropriate instruments.
That verification step is critical. Stored energy can linger even after you flip a switch. A hydraulic line may still hold pressure, a capacitor may still hold a charge, or a raised component may still be ready to drop under gravity. Proper LOTO means accounting for every form of energy in the system, not just the obvious power cord.
Types of Hazardous Energy
Most people think of electricity when they hear “hazardous energy,” but LOTO covers a much wider range. OSHA identifies seven categories: electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and gravitational (or potential) energy. A conveyor belt stores mechanical energy in its moving parts. A steam line holds thermal energy. A compressed air system contains pneumatic energy. A chemical reactor may hold pressurized or reactive substances.
Each energy source requires its own isolation point and its own lock. A single piece of equipment might have three, five, or even more energy sources that all need to be controlled before work begins. This is why written, equipment-specific procedures matter so much. Relying on memory or general knowledge increases the chance that a worker overlooks one energy source.
What Employers Are Required to Do
OSHA requires employers to build a full energy control program with three pillars: written procedures, employee training, and periodic inspections.
Written procedures must be developed and documented for each piece of equipment covered by the standard. These aren’t generic checklists. They need to identify the specific energy sources, the specific isolation points, and the specific steps to verify that energy has been controlled. The only exception is when a machine has a single energy source that can be easily identified and fully de-energized in one step, with no stored energy remaining.
Training must cover three groups of employees. “Authorized” employees are the ones who actually apply locks and tags and perform the maintenance. “Affected” employees are those who operate or work near the equipment being serviced. And “other” employees are anyone in the area who might encounter locked-out equipment. Each group needs to understand their role. Authorized employees need hands-on skill in applying and removing energy controls. Affected and other employees need to understand what a lock and tag mean and why they must never attempt to restart locked-out equipment.
Periodic inspections must happen at least once a year for each energy control procedure. Each inspection has two required components: a review of the procedure itself and a review of each employee’s responsibilities under that procedure. If an inspection reveals gaps in knowledge or compliance, the employer must retrain the relevant employees and certify that retraining was completed.
When LOTO Doesn’t Apply
Not every piece of equipment requires formal lockout tagout. The most common exception is cord-and-plug connected equipment, like a drill press or a portable grinder that plugs into a wall outlet. If the worker performing the maintenance can simply unplug the equipment and keep the plug within sight and under their exclusive control the entire time, a full LOTO procedure isn’t required. The unplugged cord effectively serves as both the isolation and the lock.
The standard also doesn’t apply to routine, minor adjustments that are part of normal production operations, as long as the work is routine, repetitive, and integral to the use of the equipment, and the employer provides effective alternative protection. Hot tap operations on pressurized pipelines are similarly excluded under specific conditions.
Group Lockout for Larger Jobs
When multiple workers need to service the same equipment at the same time, a group lockout procedure is used. The principle stays the same: every individual worker must be protected from unexpected startup. In practice, this typically involves a primary authorized employee who applies the initial lockout, and then each additional worker attaches their own personal lock to a group lockbox or multi-lock device. The equipment cannot be re-energized until every single person has removed their individual lock, confirming they are clear of the machine.
This is especially common during large maintenance shutdowns, turnarounds at manufacturing plants, or any job where crews work in shifts. If a shift change happens mid-job, the off-going workers must remove their locks and the on-coming workers must apply theirs in a continuous sequence, so the equipment is never left unprotected during the transition.
Why Violations Are So Common
Given how straightforward the concept sounds, it’s worth understanding why lockout tagout remains one of OSHA’s top cited violations year after year. The most frequent problems are missing or incomplete written procedures, inadequate training, and failure to conduct annual inspections. Many workplaces have LOTO programs on paper but fall short in execution: workers take shortcuts because they’ve done a quick repair “a hundred times,” procedures aren’t updated when equipment is modified, or inspections become rubber-stamp exercises rather than genuine reviews.
The consequences of skipping LOTO are severe and immediate. Unlike hazards that build up over years of exposure, an unexpected machine startup can kill or amputate in a fraction of a second. The 120 deaths and 50,000 injuries that proper LOTO prevents each year represent real incidents, primarily involving crushing, amputation, electrocution, and burns, that happen when someone works on a machine that suddenly powers on or releases stored energy.
Lockout vs. Tagout: Which Is Required
OSHA’s standard is clear that lockout is the preferred method. Tagout alone, using only a warning tag without a physical lock, is permitted only when an energy isolating device is not capable of being locked out. Even then, the employer must prove that their tagout program provides “full employee protection” equivalent to a lock. In practical terms, this means most workplaces should be using locks. If your equipment’s circuit breakers or valves can accept a lock, tags alone won’t satisfy the standard.
When tagout is used alone, employers are required to take additional steps to make it as effective as a lock. This might include removing a fuse, blocking a valve closed, or using a second isolation method that creates a physical barrier beyond the tag. The tag itself must be durable enough to withstand the environment, standardized in format across the workplace, substantial enough that it can’t be accidentally detached, and clearly identify the employee who attached it.