Working with industrial machinery can involve serious risks, especially during maintenance and servicing. A machine may appear to be switched off, but electrical power, hydraulic pressure, compressed air, heat, gravity, or mechanical energy can still create a dangerous situation.

This is why Lockout Tagout (LOTO) is an important part of workplace safety.

Lockout Tagout is a safety procedure used to shut down machinery, isolate hazardous energy sources, and prevent equipment from being accidentally restarted while maintenance or servicing is being performed.

In simple terms, LOTO helps make sure that a machine is not only turned off but also properly isolated and safe to work on.

In the United States, OSHA's 29 CFR 1910.147 establishes requirements for controlling hazardous energy during applicable servicing and maintenance activities.

This guide explains what LOTO means, how the lockout tagout procedure works, the different types of hazardous energy, common mistakes, employee training requirements, and the role of proper lockout equipment.

What Does Lockout Tagout Mean?

LOTO stands for Lockout Tagout.

The terms "lockout" and "tagout" describe two related parts of an energy-control process.

Lockout means physically securing an energy-isolating device so it cannot be operated. A lockout device and personal safety lock help prevent the equipment from being re-energized.

Tagout means attaching a warning tag to an energy-isolating device. The tag communicates that the equipment is under maintenance and must not be operated.

The main difference is straightforward:

• Lockout provides physical restraint.
• Tagout provides a warning.

Because a tag does not provide the same physical restraint as a lock, OSHA has specific requirements for situations where tagout is used instead of lockout.

Why Is Lockout Tagout Important?

Industrial equipment can contain several forms of hazardous energy. Turning off a machine's normal operating controls does not necessarily eliminate those hazards.

For example, a machine could still contain:

• Electrical energy
• Hydraulic pressure
• Pneumatic pressure
• Mechanical energy
• Stored spring energy
• Gravitational energy
• Thermal energy
• Pressurized fluids or gases
• Stored electrical charge
• Chemical energy

If an energy source is not identified and controlled, it could be released unexpectedly while someone is working on the equipment.

A proper lockout tagout procedure gives employees a consistent process for identifying, isolating, and verifying hazardous energy before maintenance begins.

An effective LOTO program generally includes:

• Written energy-control procedures
• Employee training
• Suitable lockout tagout devices
• Machine-specific isolation procedures
• Verification of energy isolation
• Periodic inspections
• Clear communication between employees

What Is Hazardous Energy?

Hazardous energy is energy that can cause injury when it is unexpectedly released, transferred, or activated.

Different machines can present different energy hazards, so workers should identify all relevant energy sources before starting maintenance.

Electrical Energy

Electrical energy is one of the most common hazards in industrial equipment.

It can be present in:

• Circuit breakers
• Disconnect switches
• Motors
• Control panels
• Capacitors
• Batteries
• UPS systems
• Electrical wiring

Switching a machine off does not necessarily mean that all electrical energy has been removed. The applicable energy-control procedure should identify the correct isolation points and verification method.

Mechanical Energy

Mechanical energy can be stored in moving or tensioned components.

Examples include:

• Rotating shafts
• Flywheels
• Springs
• Counterweights
• Moving machine parts
• Belts and chains

Even after the main power is disconnected, a component may continue to move or have the potential to move.

Hydraulic Energy

Hydraulic equipment can retain pressure after shutdown.

A pressurized hydraulic cylinder, hose, or component can move unexpectedly if the stored pressure is not properly controlled.

Depending on the equipment and procedure, hydraulic energy may need to be isolated, relieved, or otherwise controlled before work begins.

Pneumatic Energy

Compressed air can remain inside pipes, tanks, hoses, and cylinders.

A pneumatic system may therefore remain capable of movement even after the main machine has been shut down.

Proper isolation and depressurization are important parts of controlling pneumatic energy.

Thermal Energy

Steam, heated liquids, hot surfaces, and other thermal hazards can remain dangerous after equipment has been turned off.

Depending on the equipment, workers may need to allow components to cool or otherwise control the thermal hazard before beginning maintenance.

Gravitational Energy

Raised or suspended equipment can fall because of gravity.

Examples include:

• Elevated machine components
• Raised platforms
• Suspended loads
• Counterbalanced systems

These components may need to be lowered, blocked, supported, or otherwise secured according to the applicable procedure.

Chemical Energy

Chemical systems can contain hazardous substances, pressure, heat, or reactive materials.

Energy-control procedures should account for chemical hazards when servicing equipment connected to chemical processes.

The key principle is simple: identify every energy source that could create a hazard before work begins.

What Is an Energy-Isolating Device?

An energy-isolating device is a mechanical device that physically prevents energy from being transmitted or released.

Examples can include:

• Circuit breakers
• Disconnect switches
• Ball valves
• Gate valves
• Line valves
• Disconnecting couplings
• Blind flanges

Not every machine control is an energy-isolating device.

For example, a push button, selector switch, or software control may stop equipment from operating but normally does not physically isolate the energy source.

This is why pressing a machine's STOP button is not the same as completing a lockout tagout procedure.

Lockout vs. Tagout: What Is the Difference?

Lockout and tagout are often discussed together, but they provide different types of protection.

Lockout

Lockout uses a physical device to secure an energy-isolating device in a safe position.

Common lockout tagout equipment includes:

• Safety padlocks
• Circuit breaker lockouts
• Valve lockouts
• Plug lockouts
• Cable lockouts
• Lockout hasps
• Group lockout boxes

The lockout device should be suitable for the specific isolation point and working conditions.

Tagout

Tagout uses a warning tag attached to an energy-isolating device.

A tag typically communicates that:

• The equipment is being serviced
• The equipment must not be operated
• The energy-isolating device must not be moved

Because a warning tag does not physically prevent operation, tagout has different requirements under OSHA.

Where an energy-isolating device can be locked out, OSHA generally requires lockout unless the employer can demonstrate that a tagout procedure provides equivalent protection as required by the standard.

What Is the Lockout Tagout Procedure?

The exact LOTO procedure depends on the machinery, workplace, and energy sources involved.

However, the process can generally be broken down into eight basic steps.

1. Prepare for Equipment Shutdown

Before shutting down machinery, identify the equipment and determine what types of hazardous energy are present.

Review the machine-specific energy-control procedure and identify:

• Energy sources
• Energy-isolating devices
• Isolation points
• Stored-energy hazards
• Required lockout devices
• Verification methods

Proper preparation helps reduce the chance of missing an energy source.

2. Notify Affected Employees

Employees who operate the equipment or work in the surrounding area should be informed before the shutdown.

They should understand:

• Which equipment is being shut down
• Why the equipment is being serviced
• How the shutdown may affect operations
• That the equipment must not be restarted

Clear communication helps prevent someone from attempting to operate equipment during maintenance.

3. Shut Down the Equipment

Follow the machine's normal shutdown procedure.

An orderly shutdown can help prevent additional hazards and prepare the equipment for isolation.

The shutdown process should follow the equipment's established procedure rather than relying only on the emergency stop or normal operating controls.

4. Isolate All Hazardous Energy Sources

After the equipment has been shut down, operate all required energy-isolating devices.

Depending on the machinery, this may include:

• Electrical disconnects
• Circuit breakers
• Hydraulic valves
• Pneumatic valves
• Gas valves
• Steam valves
• Mechanical isolation devices

It is important not to assume that one isolation point makes the entire machine safe.

5. Apply Lockout Devices and Tags

Apply the appropriate lockout devices to each required isolation point.

A basic sequence can be understood as:

Isolation point → Lockout device → Personal lock → Identification tag

Authorized employees should apply locks and tags according to the workplace's established procedure.

Lockout equipment should fit the isolation device and clearly identify the employee responsible for the lock where required.

6. Release Stored Energy

One of the most commonly overlooked parts of LOTO is stored energy.

After isolation, remaining energy may need to be:

• Released
• Drained
• Vented
• Discharged
• Bled
• Blocked
• Restrained
• Grounded
• Cooled

For example, hydraulic pressure may need to be relieved, compressed air may need to be released, electrical charge may need to be discharged, and raised components may need to be mechanically secured.

7. Verify Energy Isolation

Verification is a critical step in the lockout tagout process.

Before maintenance starts, authorized employees should confirm that the equipment has actually been isolated.

Depending on the equipment, verification may involve:

• Attempting the normal start control
• Testing for electrical energy
• Checking pressure gauges
• Confirming zero pressure
• Inspecting mechanical restraints
• Using appropriate test equipment

The verification method should match the energy hazards involved.

The goal is to confirm that the equipment cannot unexpectedly start or release hazardous energy.

8. Perform the Maintenance Work

Once hazardous energy has been isolated and the isolation has been verified, authorized employees can begin servicing or maintenance.

Locks and tags should remain in place during the work unless a controlled procedure requires temporary removal or re-energization.

If the job changes or an unexpected energy source is discovered, work should stop and the energy-control procedure should be reassessed.

Who Needs Lockout Tagout Training?

LOTO training should reflect an employee's role and responsibilities.

Authorized Employees

Authorized employees perform servicing or maintenance and are responsible for applying and removing energy-control devices.

They need to understand:

• Hazardous energy
• Energy-isolation procedures
• Lockout devices
• Stored-energy hazards
• Verification requirements
• Safe removal and restoration procedures

Affected Employees

Affected employees typically operate or use equipment that is being serviced or work in an area where servicing takes place.

They need to understand the purpose of LOTO and know that locked or tagged equipment must not be restarted.

Other Employees

Other employees who may work around the equipment should also understand that equipment under LOTO must not be operated, restarted, or re-energized.

Retraining may be necessary when job assignments, machinery, processes, or procedures change, or when an inspection identifies deficiencies.

How Often Should LOTO Procedures Be Inspected?

Under OSHA 1910.147, applicable energy-control procedures must be inspected at least once every year.

The inspection helps determine whether:

• The energy-control procedure is being followed
• Employees understand their responsibilities
• The procedure continues to provide effective protection

Employers should also review procedures when equipment, processes, or work practices change.

Any problems identified during an inspection should be corrected, and additional training should be provided when necessary.

Common Lockout Tagout Mistakes to Avoid

A LOTO program can become less effective when employees skip steps or rely on assumptions.

Here are some common mistakes to watch for.

Relying Only on the Stop Button

A stop button controls machine operation but normally does not physically isolate hazardous energy.

Missing an Energy Source

A machine may have electrical, hydraulic, pneumatic, mechanical, thermal, or other energy sources.

Forgetting Stored Energy

Energy can remain after shutdown. Pressure, heat, gravity, electrical charge, and mechanical tension all need to be considered.

Skipping Verification

Never assume that isolation was successful. Follow the required verification process before maintenance begins.

Using Inappropriate Lockout Equipment

A lockout device should fit the isolation point and be suitable for the environment in which it will be used.

Relying on a Generic Procedure

Complex machinery may require a detailed, machine-specific energy-control procedure.

Poor Communication

Employees operating or working near the equipment need to know when it has been removed from service.

Failing to Update Procedures

Equipment modifications, new energy sources, process changes, and maintenance changes may require the LOTO procedure to be reviewed.

LOTO vs. Machine Guarding

Lockout Tagout and machine guarding are not the same thing.

Machine guarding is generally designed to protect employees from hazards associated with moving machinery during operation.

LOTO is used to control hazardous energy during applicable servicing and maintenance activities.

For example, if a machine guard must be removed during maintenance and doing so exposes a worker to unexpected movement or energization, an appropriate energy-control procedure may be required.

Both machine guarding and LOTO play important roles in workplace safety, but they address different hazards and situations.

Lockout Tagout Checklist

A simple checklist can help workers remember the major steps involved in energy control.

Before maintenance begins, confirm that the applicable procedure addresses:

• Equipment identification
• All hazardous energy sources
• Machine-specific procedures
• Employee notification
• Equipment shutdown
• Energy isolation
• Lockout devices and tags
• Stored-energy control
• Energy verification
• Maintenance work
• Area inspection before restoration
• Safe employee positioning
• Lock and tag removal
• Controlled energy restoration
• Employee notification after restoration

A checklist should support the workplace's actual LOTO procedure. It should not be used as a substitute for a detailed energy-control procedure when one is required.

Choosing the Right Lockout Tagout Equipment

A written energy-control procedure is only one part of a successful LOTO program. Employees also need suitable equipment to isolate the energy sources found on their machinery.

Depending on the application, workplaces may use:

• Safety lockout padlocks
• Circuit breaker lockouts
• Valve lockouts
• Plug lockouts
• Cable lockouts
• Lockout hasps
• Lockout tags
• Group lockout boxes

The correct equipment depends on the type of energy, isolation device, working environment, number of employees involved, and applicable workplace requirements.

E-Square Alliance provides lockout and safety solutions through E-Square Alliance, offering equipment for a range of energy-isolation applications.

Frequently Asked Questions About LOTO

What does LOTO stand for?

LOTO stands for Lockout Tagout. It is a safety procedure used to control hazardous energy during applicable servicing and maintenance activities.

What is the purpose of Lockout Tagout?

The purpose of LOTO is to prevent unexpected startup, energization, or release of hazardous energy while employees are performing covered servicing or maintenance work.

Is turning off a machine enough for LOTO?

No. Simply switching off a machine does not necessarily isolate all hazardous energy. The applicable procedure should identify the required energy-isolating devices, control stored energy, and include verification.

What are examples of LOTO devices?

Examples include safety padlocks, circuit breaker lockouts, valve lockouts, plug lockouts, cable lockouts, lockout hasps, tags, and group lockout boxes.

What is the difference between lockout and tagout?

Lockout physically secures an energy-isolating device, while tagout provides a warning that the equipment must not be operated. OSHA has specific requirements governing the use of tagout.

How often should LOTO procedures be inspected?

Applicable energy-control procedures must be inspected at least annually under OSHA 1910.147.

Who applies a lockout device?

Authorized employees who perform servicing or maintenance are responsible for applying and removing energy-control devices according to the established procedure.

Final Thoughts on Lockout Tagout Safety

Lockout Tagout is based on a simple but important principle: hazardous energy must be properly controlled before applicable servicing or maintenance begins.

Effective LOTO involves more than placing a lock on a switch. Workers need to identify all relevant energy sources, isolate them correctly, control stored energy, verify the isolation, and follow the appropriate procedure.

A strong lockout tagout program also requires employee training, suitable LOTO equipment, regular inspections, clear communication, and machine-specific procedures that are kept up to date.

When safe energy isolation becomes a routine part of maintenance, workers are better prepared to prevent unexpected machine startup and hazardous energy release.

For workplaces looking for suitable lockout and energy-control equipment, E-Square Alliance provide a range of solutions designed for different industrial applications.