Lockout tagout—commonly shortened to LOTO—is a structured method of controlling hazardous energy before servicing or maintaining machinery. It is designed to prevent unexpected start-up, energization or the release of stored energy while people are working in a danger zone.
A reliable LOTO process is more than placing a padlock on a switch. It combines a site-specific energy control programme, clear machine procedures, trained people, correctly selected lockout devices and verification that every hazardous energy source has been isolated.
Important: This guide provides general industrial safety information. Employers must assess their own equipment, tasks and applicable legal requirements, and must establish site-specific procedures before work begins.
What does lockout tagout mean?
Under the U.S. Occupational Safety and Health Administration’s general-industry standard, 29 CFR 1910.147, hazardous energy must be controlled during servicing and maintenance when unexpected energization, start-up or the release of stored energy could harm employees.
Lockout means placing a lockout device on an energy-isolating device so the machine or equipment cannot be operated until that device is removed. Tagout means attaching a prominent warning tag to an energy-isolating device to indicate that the equipment must not be operated.
The distinction matters: a lockout device provides physical restraint, while a tag communicates a warning. Where an energy-isolating device is capable of being locked out, OSHA’s general-industry rule requires lockout unless the employer can demonstrate that a tagout programme provides full employee protection.
Why hazardous energy is not limited to electricity
Electrical power is only one part of an energy-isolation assessment. Industrial machinery may contain several energy sources at the same time, and some remain hazardous even after the normal power control has been switched off.
| Energy type | Typical examples | Possible control considerations |
|---|---|---|
| Electrical | Disconnects, circuit breakers, plugs, batteries and capacitors | Open the energy-isolating device, apply a compatible lockout and verify the absence of energy using an appropriate method. |
| Mechanical | Flywheels, springs, elevated parts, rotating components and gravity | Stop movement, lower or block suspended components and restrain stored mechanical force. |
| Hydraulic | Presses, cylinders, accumulators and lifting systems | Isolate pumps, relieve pressure and block components that could move. |
| Pneumatic | Compressed-air lines, actuators, receivers and air tools | Close and secure valves, bleed pressure and prevent reaccumulation. |
| Chemical | Process lines, reactive materials, gases and cleaning chemicals | Isolate flow, secure valves and control any residual material according to the process risk. |
| Thermal | Steam, hot surfaces, furnaces, cryogenic systems and heated fluids | Isolate the source and allow temperature or pressure to reach a verified safe condition. |
OSHA notes that machines may contain mechanical, hydraulic, pneumatic, chemical, thermal or other forms of hazardous energy. A complete procedure must identify and control all applicable sources—not only the most obvious one.
When is a LOTO procedure used?
LOTO is generally associated with servicing and maintenance activities where a person could be exposed to hazardous energy. Examples include:
- repairing, cleaning or unjamming machinery;
- removing guards or entering a machine’s danger zone;
- adjusting, inspecting or replacing components;
- working on valves, pipelines or pressure systems;
- performing electrical, mechanical or process maintenance;
- conducting work across a shift change or with multiple maintenance employees.
Applicability depends on the task, the equipment and the governing jurisdiction. For example, OSHA’s 29 CFR 1910.147 applies to specified general-industry servicing and maintenance work, while other sectors and electrical work may be covered by different requirements. A facility should never rely on a generic online checklist to decide whether a particular task is exempt.
The six core steps of a lockout tagout procedure
The exact method must be written for the machine and energy-isolation points involved. The following six-stage sequence provides a practical overview of the application of energy control described by OSHA.
1. Prepare for shutdown
An authorized employee reviews the machine-specific procedure, identifies every hazardous energy source and understands the type and magnitude of the available energy. The employee also confirms which isolation points, tools and lockout devices will be required.
Affected employees should be notified before lockout or tagout devices are applied. The communication should explain which equipment will be unavailable and why.
2. Shut down the machine normally
Use the established operating controls to stop the equipment in an orderly manner. This can reduce the risk of creating additional hazards during shutdown. Pressing a stop button is not, by itself, energy isolation.
3. Isolate every hazardous energy source
Operate the appropriate energy-isolating devices—such as disconnect switches, line valves or blocks—to physically separate the equipment from its energy sources. Control-circuit devices, selector switches, emergency stops and software commands generally do not replace an energy-isolating device.
4. Apply personal lockout and tagout devices
Each authorized employee applies an individually identified lock to the applicable isolation point or approved group-lockout system. The device must fit the isolation point and hold it in a safe or off position.
Different isolation points require different hardware. A facility may need circuit breaker lockouts, valve lockouts, cable lockouts, plug lockouts or a lockout hasp that allows multiple authorized employees to attach personal locks.
5. Control stored or residual energy
After isolation devices have been secured, stored energy must be released, disconnected, restrained or otherwise rendered safe. This may require bleeding pressure, discharging capacitors, lowering suspended loads, blocking moving components, allowing hot parts to cool or restraining springs.
If hazardous energy could reaccumulate during the work, the procedure must include continued monitoring or additional verification.
6. Verify isolation before work begins
The authorized employee must verify that the equipment has been isolated and de-energized. Depending on the system, verification may include attempting a normal start after ensuring no person is exposed, testing with an appropriate instrument, checking pressure indicators or using more than one verification method.
After a try-start test, operating controls should be returned to the neutral or off position. Work begins only after the authorized employee has confirmed a verified zero-energy or otherwise controlled-energy state in accordance with the procedure.
How equipment is safely returned to service
Re-energization needs its own controlled sequence. Before removing locks and restoring energy:
- inspect the equipment and work area;
- remove nonessential tools, materials and temporary items;
- confirm that machine components are operationally intact;
- ensure that all employees are safely positioned or clear;
- have each authorized employee remove their own personal device, except where a compliant employer procedure specifically addresses an unavailable employee;
- notify affected employees that the devices have been removed and the equipment is ready to return to service.
Group lockout, contractor work and shift changes require defined transfer and accountability procedures so that every exposed person remains protected throughout the job.
Who is responsible for LOTO?
| Role | Typical responsibility |
|---|---|
| Authorized employee | Applies lockout or tagout to perform servicing or maintenance and is trained to recognize and control the hazardous energy involved. |
| Affected employee | Operates or uses the equipment being serviced, or works in the area, and must understand the purpose and restrictions of the energy control procedure. |
| Other employee | May work in an area where LOTO is used and must understand that locked or tagged equipment must not be started, re-energized or disturbed. |
One person may perform more than one role at different times. An affected employee becomes an authorized employee when that person performs servicing or maintenance covered by the procedure and has received the required training.
How to select lockout tagout devices
Device selection should begin with the energy-isolation points—not with a general shopping list. Photograph or document each disconnect, breaker, valve, plug and mechanical restraint, then confirm the dimensions and operating conditions.
A practical LOTO hardware system may include:
- Safety padlocks: individually keyed and identified for personal energy control;
- Lockout hasps: allow several people to place personal locks on one isolation point;
- Circuit breaker lockouts: selected to match the breaker type, dimensions and toggle geometry;
- Valve lockouts: configured for gate, ball, butterfly, plug or other valve types;
- Cable lockouts: useful for multiple or unusually shaped isolation points where approved by the procedure;
- Group lock boxes: support accountable protection for teams and complex multi-energy jobs;
- Tags and identification: communicate who applied the device and warn against operation;
- Stations and kits: keep approved devices organized and accessible near the work area.
Under OSHA’s general-industry rule, lockout and tagout devices must be durable, standardized, substantial and identifiable, and they must be used only for energy control. Explore PROLOCKEY lockout tagout products or review a configured lockout kit as a starting point for device planning.
Common lockout tagout mistakes
Treating the stop button as isolation
A stop button or control-panel switch may interrupt a control signal without physically isolating the energy source. The procedure must identify the actual energy-isolating device.
Identifying only the electrical supply
Gravity, pressure, heat, springs and process materials can remain hazardous after electrical power has been disconnected.
Skipping verification
Applying a lock does not prove that the correct disconnect was opened or that every source has been controlled. Verification is a required step before work begins.
Using a shared personal lock
Every exposed authorized employee needs personal protection and accountability. Group systems should preserve that protection rather than relying on one untraceable lock for the whole team.
Choosing a device without checking fit
A breaker or valve lockout that does not fit securely may not hold the isolating device in the required safe position. Record the isolation-point dimensions before standardizing hardware.
Using one generic procedure for dissimilar machines
Written procedures need enough detail to identify the equipment, isolation sequence, device placement, stored-energy controls and verification method. Generic procedures should only be used where the equipment and control method genuinely allow it.
Ignoring inspections and changes
OSHA requires a periodic inspection of each covered energy control procedure at least annually. Procedures should also be reviewed when equipment, responsibilities or control methods change, and deficiencies must be corrected.
Building an effective energy control programme
A mature LOTO programme connects policy, people, procedures and hardware. A useful implementation sequence is:
- inventory machinery and energy-isolation points;
- conduct task- and machine-specific hazardous-energy assessments;
- write clear procedures with photographs or isolation diagrams where useful;
- select and standardize devices based on the actual isolation points;
- train authorized, affected and other employees for their responsibilities;
- define contractor, group-lockout and shift-transfer rules;
- conduct periodic inspections and document corrective actions;
- update the programme when machinery, processes or regulations change.
Hardware supports the programme, but it cannot replace risk assessment, training, supervision or verification. The best device is the one that fits the identified isolation point, works within the written procedure and remains reliable in the actual workplace environment.
Lockout tagout FAQ
What is the main purpose of lockout tagout?
The purpose of LOTO is to prevent unexpected energization, start-up or hazardous stored-energy release while servicing or maintenance is being performed.
Is turning off a machine enough?
No. A normal stop command does not necessarily isolate the machine from its energy sources. The applicable energy-isolating devices must be operated, secured and verified according to the written procedure.
What is the difference between lockout and tagout?
Lockout physically restrains an energy-isolating device in a safe position. Tagout places a warning on the device but does not provide the same physical restraint.
Who can apply a LOTO lock?
An authorized employee who has received the required training and is implementing the employer’s energy control procedure applies the personal lockout or tagout device.
Can one safety padlock be used for several workers?
Each authorized employee exposed to the hazardous energy should maintain personal protection and control. Group-lockout arrangements must provide protection equivalent to personal lockout and maintain clear accountability for every participating employee.
How often should LOTO procedures be inspected?
For workplaces covered by OSHA 29 CFR 1910.147, each energy control procedure must be periodically inspected at least annually. Additional reviews are appropriate when equipment, processes, personnel responsibilities or control methods change.
Official references
- OSHA 29 CFR 1910.147 — The Control of Hazardous Energy
- OSHA — Control of Hazardous Energy Overview
- OSHA eTool — Application of Energy Control
- OSHA eTool — Employee Training and Communication
- OSHA eTool — Periodic Inspections
Need help matching lockout devices to your isolation points? PROLOCKEY supports industrial buyers with lockout tagout product selection, configuration and documentation. Contact the PROLOCKEY team with photographs and dimensions of the equipment you need to isolate.