Lockout/tagout (LOTO) is a safety procedure that isolates machines and equipment from their energy sources and keeps them in a safe, de-energized state during servicing and maintenance. Authorized employees apply locks or tags to energy-isolating devices so equipment cannot start up or release stored energy while someone is working on it.
In the United States, LOTO is governed by OSHA's Control of Hazardous Energy standard, 29 CFR 1910.147. OSHA notes that craft workers, electricians, machine operators and laborers who routinely service equipment face the greatest risk of injury when hazardous energy is not controlled.
What Is Lockout/Tagout (LOTO)?
29 CFR 1910.147 covers the servicing and maintenance of machines and equipment in which the unexpected energization or start-up of the equipment, or the release of stored energy, could harm employees. The standard requires employers to establish a program of energy control procedures, employee training and periodic inspections.
The two parts of the term describe two different protective methods:
- Lockout means placing a lockout device, such as a keyed padlock, on an energy-isolating device so the equipment cannot be operated until the lock is removed.
- Tagout means placing a prominent warning tag on an energy-isolating device to indicate that the equipment must not be operated until the tag is removed.
Lockout is the preferred method. If an energy-isolating device is capable of being locked out, the employer must use lockout unless it can show that a tagout program provides full employee protection. Tagout alone is allowed when a device cannot accept a lock.
Types of hazardous energy
Hazardous energy is not limited to electricity. A LOTO procedure must address every source that could move, heat, pressurize or shock, including electrical, mechanical, hydraulic, pneumatic, chemical and thermal energy. Stored or residual energy, such as a charged capacitor, a raised ram, a compressed spring or pressure trapped in a line, must also be relieved or restrained.
Key OSHA Lockout/Tagout Requirements
Energy control program
Employers must have a written program made up of energy control procedures, employee training and periodic inspections. Procedures must be specific to the equipment and must spell out the scope, purpose, authorization, rules and techniques for controlling energy, including steps for shutting down, isolating, blocking and securing machines and for verifying isolation.
Lockout and tagout devices
Devices must be provided by the employer and must be durable, standardized, substantial and identifiable. Each device must identify the employee who applied it. Tagout devices must be attached with a non-reusable, self-locking fastener with an unlocking strength of no less than 50 pounds.
Periodic inspection
The employer must inspect each energy control procedure at least annually. An authorized employee other than the ones using the procedure performs the inspection and reviews responsibilities with the employees involved. The employer must certify each inspection with the machine, date, employees included and the inspector's name.
Training
OSHA defines three groups of employees, each with different training needs:
- Authorized employees lock or tag out equipment to perform servicing. They need training on recognizing hazardous energy sources, the type and magnitude of energy present and the methods for isolation and control.
- Affected employees operate or work near equipment being serviced. They need instruction on the purpose and use of the procedure.
- Other employees work in areas where energy control may be used. They must understand the procedure and the prohibition on restarting locked or tagged equipment.
Retraining is required when job assignments, machines, processes or procedures change, or when an inspection reveals deviations or gaps in knowledge.
Common exceptions
The standard does not apply to work on cord and plug connected equipment when it is unplugged and the plug is under the exclusive control of the employee doing the work. Minor tool changes and adjustments during normal production are also excluded if they are routine, repetitive and integral to the use of the equipment, and if alternative measures provide effective protection.
Lockout/Tagout Steps: How to Apply LOTO
1910.147(d) sets out the sequence for applying energy control. A typical procedure follows these steps:
- Prepare for shutdown. The authorized employee identifies all energy sources, their magnitude and the hazards, and the method for controlling them.
- Notify affected employees. Tell operators and nearby workers that the equipment will be shut down and locked out.
- Shut down the equipment. Use the normal stopping procedure to avoid creating additional hazards.
- Isolate the energy. Operate every energy-isolating device, such as disconnects, valves and breakers, to separate the equipment from its energy sources.
- Apply locks and tags. Each authorized employee attaches a personal lock or tag to each isolating device.
- Release or restrain stored energy. Bleed lines, block parts, discharge capacitors and relieve pressure. Continue to verify if stored energy could build up again.
- Verify isolation. Before starting work, attempt to start the equipment or test for zero energy, then return controls to the off position.
When work is complete, the release procedure in 1910.147(e) requires inspecting the work area, removing tools, making sure all employees are safely positioned, notifying affected employees and having each lock removed by the employee who applied it. OSHA allows a supervisor-directed removal only under specific conditions, such as verifying the authorized employee is not at the facility and informing them before they return.
Group Lockout, Shift Changes and Contractors
When a crew services the same equipment, group lockout procedures must give each authorized employee the same level of protection as a personal lock. Common methods include a lockbox where the primary authorized employee secures the keys and each worker adds a personal lock to the box.
The standard also requires procedures to maintain continuity of protection across shift or personnel changes. When outside contractors perform servicing, the host employer and contractor must inform each other of their energy control procedures, and the host must make sure its employees understand and follow the contractor's program.
Lockout/Tagout vs. Machine Guarding
Machine guarding protects operators during normal production by preventing contact with moving parts. Lockout/tagout protects workers during servicing and maintenance, when guards are often removed or bypassed. If servicing requires an employee to remove a guard or place any part of the body where it could be caught by machine motion, LOTO generally applies. Both controls belong in the hierarchy of controls as engineering and administrative safeguards.
Common LOTO Mistakes to Avoid
- Using generic procedures. A single procedure for every machine rarely identifies every energy source. Write equipment-specific procedures.
- Skipping verification. Pressing the start button or testing for voltage after isolation is what confirms the equipment is truly de-energized.
- Ignoring stored energy. Gravity, springs, hydraulics and capacitors can cause injuries even after the main disconnect is off.
- Sharing locks or keys. Each authorized employee should control their own lock and key.
- Letting annual inspections lapse. Missing or undocumented periodic inspections are a frequent finding during audits.
Best Practices for a Strong LOTO Program
Post a photo-based procedure at each machine showing the location of every isolation point. Keep an equipment inventory that links each asset to its current procedure. Use color-coded or individually keyed locks so ownership is clear. Include LOTO in your job hazard analysis process for maintenance tasks, and review incidents and near misses involving unexpected start-up to find gaps in procedures or training.
How SMS360 Helps
SMS360's Lockout/Tagout module helps teams keep energy control procedures organized and accessible. Safety managers can maintain equipment-specific procedures, track annual inspections and training records, assign follow-up actions and set reminders for upcoming reviews. Mobile access lets authorized employees view the correct procedure at the machine, and centralized records make it easier to show compliance during audits.
Frequently Asked Questions
What is the OSHA standard for lockout/tagout?
The OSHA lockout/tagout standard is 29 CFR 1910.147, The Control of Hazardous Energy. It applies to general industry servicing and maintenance where unexpected start-up or release of stored energy could injure workers. Related rules cover specific situations, such as 1910.333 for electrical work practices. Construction, agriculture and maritime operations are covered by other standards rather than 1910.147.
How often must LOTO procedures be inspected?
OSHA requires a periodic inspection of each energy control procedure at least annually. An authorized employee who is not using the procedure being inspected must conduct it. The inspection should confirm the procedure is being followed and correct any deviations. The employer must certify the inspection, recording the machine or equipment, the date, the employees included and the person who performed it.
Who can remove a lockout device?
Each lockout or tagout device must be removed by the authorized employee who applied it. If that employee is not available, OSHA allows removal under the direction of the employer only when the employer verifies the employee is not at the facility, makes all reasonable efforts to contact them and ensures they know the lock was removed before they resume work.
When can tagout be used instead of lockout?
Tagout alone may be used when an energy-isolating device cannot accept a lock. If the device can be locked out, the employer must use lockout unless it can show that its tagout program provides full employee protection, equivalent to lockout. This usually means adding measures such as removing an isolating circuit element, blocking a control switch or opening an extra disconnecting device.
