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Title: Lockout-tagout  
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Subject: Occupational safety and health, Contractor management, NFPA 70E, Locksmithing, Key control
Collection: Electrical Engineering, Occupational Safety and Health, Safety Codes
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Folding lockout scissor clamp, allowing six contractor padlocks to lock out one device.
Lockout-tagout (LOTO)

or lock and tag is a safety procedure which is used in industry and research settings to ensure that dangerous machines are properly shut off and not started up again prior to the completion of maintenance or servicing work. It requires that hazardous power sources be "isolated and rendered inoperative" before any repair procedure is started. "Lock and tag" works in conjunction with a lock usually locking the device or the power source with the hasp, and placing it in such a position that no hazardous power sources can be turned on. The procedure requires that a tag be affixed to the locked device indicating that it should not be turned on.


  • Group lockout 1
  • Hazardous energy and its isolation 2
  • Site policies regarding lockout/tagout 3
    • Identification 3.1
    • The Five Security Rules 3.2
  • Industry safety standard in Canada 4
  • Industry safety standard in the United States 5
    • Compliance 5.1
    • Exceptions 5.2
  • References 6

Group lockout

When two or more subcontractors are working on different parts of a larger overall system, the locked-out device is first secured with a folding scissors clamp that has many padlock holes capable of holding it closed. Each subcontractor applies their own padlock to the clamp. The locked-out device cannot be activated until all workers have signed off on their portion of the project and removed their padlock from the clamp.

A lockout device applied to a hoist brake. This prevents unintended movement of the hoist. The lockout scissors is secured with two padlocks.

In the United States a lock selected by color, shape or size (e.g. red padlock) is used to designate a standard safety device, locking and securing hazardous energy. No two keys or locks should ever be the same. A person's lock and tag must not be removed by anyone other than the individual who installed the lock and tag unless removal is accomplished under the direction of the employer. Employer procedures and training for such removal must have been developed, documented and incorporated into the employer energy control program.[1]

Lockout-tagout in the US, has 5 required components to be fully compliant with OSHA law. The 5 components are: 1. Lockout-Tagout Procedures 2. Lockout-Tagout Training (for authorized employees and affected employees) 3. Lockout-Tagout Policy (often referred to as a program) 4. Lockout-Tagout Devices and Locks 5. Lockout-Tagout Auditing - Every 12 months, every procedure must be reviewed as well as a review of authorized employees [2]

Hazardous energy and its isolation

Tags left in place in a powerplant after it was shut down, decommissioned, and abandoned

Modern machinery can contain many hazards to workers, examples of the most common risks[3] are:

  1. Electricity
  2. Hydraulic pressure (line)
  3. Hydraulic accumulation (pump)
  4. Pneumatic compressed air
  5. Gas
  6. Steam
  7. Thermal
  8. Gravity
  9. Kinetic spring tension
  10. Many types of fluids (chemical, water, etc.)

For example a typical industrial machine may contain things like hot fluids, moving presses, blades, propellers, electrical heaters, conveyor belts with pinch points, moving chains, ultraviolet light, etc.

Disconnecting or making safe the equipment involves the removal of all energy sources and is known as isolation. The steps necessary to isolate equipment are often documented in an isolation procedure or a lockout tagout procedure. The isolation procedure generally includes the following tasks:

  1. announce shut off
  2. Identify the energy source(s)
  3. Isolate the energy source(s)
  4. Lock and Tag the energy source(s)
  5. Prove that the equipment isolation is effective

The locking and tagging of the isolation point lets others know not to de-isolate the device. To emphasize the last step above in addition to the others, the entire process can be referred to as lock, tag and try (that is, try to turn on the isolated equipment).

The National Electric Code states that a safety/service disconnect must be installed within sight of serviceable equipment. The safety disconnect ensures the equipment can be isolated and there is less chance of someone turning the power back on if they can see the work going on. These safety disconnects usually have multiple places for locks so more than one person can work on equipment safely.

In industrial processes it can be difficult to establish where the appropriate danger sources might be. For example, a food processing plant may have input and output tanks and high temperature cleaning systems connected, but not in the same room or area of the factory. It would not be unusual to have to visit several areas of the factory in order to effectively isolate a device for service (e.g., device itself for power, upstream material feeders, downstream feeders and control room).

Modern safety manufacturers provide a range of isolation devices specifically designed to fit various switches, valves and effectors. For example, most modern circuit-breakers have a provision to have a small padlock attached to prevent their activation. For other devices such as ball or gate valves, plastic pieces which either fit against the pipe and prevent movement, or clam-shell style objects, which completely surround the valve and prevent its manipulation are used.

A common feature of these devices is their bright color, usually red to increase visibility and allow workers to readily see if a device is isolated. Also, the devices are usually of such a design and construction to prevent it being removed with any moderate force. (That is to say that an isolation device does not have to stand up to a chainsaw, but if an operator forcibly removes it, it will be immediately visible that it has been tampered with).

To protect one or more circuit breakers in an electrical panel a lockout tagout device called the Panel Lockout can be used. It keeps the panel door locked and prevents the panel cover from being removed. The circuit breakers remain in the off position while electrical work is done.

Site policies regarding lockout/tagout

Many sites have the officially stated policy that only the person who tagged the device can untag it. This means that if a worker goes home after their shift without removing the tag from a device which is ready to use, then they will have to travel back to the site to untag it. Giving approval for the removal of a tag over the phone is prohibited.

While this policy might seem to be encouraging workers to take the risk of not tagging out in the first place, it is usually accompanied by a policy stating that working on a device without tagging it out will result in instant dismissal.


The tag must have an identification showing the name of the person doing the lock and tag. (CFR 1910.147 (c) (5) (ii) (c) (1) While this may be true for the United States, it is not mandatory in Europe. The lockout can also be done by a "role" e.g. the shiftleader. Using a "lockbox", the shift leader is always the last one to remove his lock, he has to verify it is safe to start up equipment.

The Five Security Rules

According to the European standard EN 50110-1, the safety procedure before working on electric equipment comprises the following five steps:

  1. disconnect completely;
  2. secure against re-connection;
  3. verify that the installation is dead;
  4. carry out earthing and short-circuiting; and
  5. provide protection against adjacent live parts.

Industry safety standard in Canada

All Canadian jurisdictions legally require lockout for certain work. However, the specific activities required for appropriate lock out are usually not specified in law. These specifics are provided through industry standards. The Canadian Standards Association's standard CSA Z460, based on industry, labour and government consultations, outlines the specific activities of a lockout program and is usually considered the appropriate standard of good practice for lock out. All Canadian health and safety legislation places a general duty on an employer to take all reasonable precautions and carrying out this standard of good practice is usually considered a mark of due diligence.

Industry safety standard in the United States

In industry this is an Occupational Safety and Health Administration (OSHA) standard, as well as for electrical NFPA 70E. OSHA’s standard on the Control of Hazardous Energy (Lockout-Tagout), found in CFR 1910.147, spells out the steps employers must take to prevent accidents associated with hazardous energy. The standard addresses practices and procedures necessary to disable machinery and prevent the release of potentially hazardous energy while maintenance or servicing activities are performed.

Two other OSHA standards also contain energy control provisions: 29 CFR 1910.269 and 1910.333. In addition, some standards relating to specific types of machinery contain deenergization requirements such as 29 CFR 1910.179(l)(2)(i)(c)(requiring the switches to be “open and locked in the open position” before performing preventive maintenance on overhead and gantry cranes).[4] The provisions of Part 1910.147 apply in conjunction with these machine-specific standards to assure that employees will be adequately protected against hazardous energy.


If employees service or maintain machines where the unexpected startup, energization, or the release of stored energy could cause injury, the OSHA standard applies, unless an equivalent level of protection can be proven. Equivalent level of protection may be achieved in some cases through SOP (standard operating procedures) and custom machine guarding solutions that are combined to establish machine control to protect the worker for specific tasks. The standard applies to all sources of energy, including, but not limited to: mechanical, electrical, hydraulic, pneumatic, chemical, and thermal energy.

The standard does not cover electrical hazards from work on, near, or with conductors or equipment in electric utilization (premise wiring) installations, which are outlined by 29 CFR Part 1910 Subpart S. You can find the specific lockout and tagout provisions for electrical shock and burn hazards in 29 CFR Part 1910.333. Controlling hazardous energy in installations for the exclusive purpose of power generation, transmission, and distribution, including related equipment for communication or metering, is covered by 29 CFR 1910.269.

The standard also does not cover the agriculture, construction, and maritime industries or oil and gas well drilling and servicing. Other standards concerning the control of hazardous energy, however, apply in many of these industries and situations.


The standard does not apply to general industry service and maintenance activities in the following situations, when:

  • Exposure to hazardous energy is controlled completely by unplugging the equipment from an electric outlet and where the employee doing the service or maintenance has exclusive control of the plug. This applies only if electricity is the only form of hazardous energy to which employees may be exposed. This exception encompasses many portable hand tools and some cord and plug connected machinery and equipment.[5]
  • An employee performs hot-tap operations on pressurized pipelines that distribute gas, steam, water, or petroleum products, for which the employer shows the following:
    • Continuity of service is essential;
    • Shutdown of the system is impractical; and
    • The employee follows documented procedures and uses special equipment that provides proven, effective employee protection.
  • The employee is performing minor tool changes or other minor servicing activities that are routine, repetitive, and integral to production, and that occur during normal production operations. In these cases, employees must have effective, alternative protection.


  1. ^ The control of hazardous energy (lockout/tagout) - 1910.147, U.S.  
  2. ^ 5-components to lockout-tagout, ESC Services, Inc., retrieved April 4, 2014 
  3. ^ 6 examples of harzourdous energy sources, Lockout-Tagout-Shop, retrieved December 23, 2014 
  4. ^ The standard provides a limited exception to the requirement that energy control procedures be documented. If an employer can demonstrate the existence of each of the eight elements listed in 1910.147(c)(4)(i), the employer is not required to document the energy control procedure. However, the exception terminates if circumstances change and any of the elements no longer exist
  5. ^ OSHA Letter of Interpretaion #25560
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