Lockout/Tagout, 29 CFR 1910.147

On October 30, 1989, the Lockout/Tagout Standard, 29 CFR 1910.147, went into effect. It was created to help reduce the death and injury rate caused by the unexpected energization or start-up of machines, or the release of stored energy.

The standard covers the servicing and maintenance of machines and equipment in which the unexpected energization, start-up or release of stored energy could cause injury [29 CFR 1910.147 (a)(l)(i), 1910.147 (a)(2)(i)]. Normal production operations, cords and plugs under exclusive control, and hot tap operations are not covered [29 CFR 1910.147 (a)(2)(ii)]. This is intended to apply to energy sources such as electrical, mechanical, hydraulic, chemical, nuclear, and thermal.

Lockout is the placement of a lockout device on an energy isolation device (circuit breaker, slide gate, line valve, disconnect switch, etc.) to ensure that the energy isolating device and equipment being controlled cannot be operated until the lockout device is removed. A lockout device utilizes a positive means such as a lock (key or combination type) to hold an energy isolating device in a safe position and prevent the energization of a machine or equipment. The lockout device must be substantial enough to prevent removal without use of excessive force or unusual techniques.

Tagout is the placement of a tagout device (a tag or other prominent warning device and a means of attachment) on an energy isolation device to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.

The lockout device shall be used unless the employer can demonstrate that the utilization of a tagout system will provide full employee protection. The tagout device shall be non-reusable, attached by hand, self-locking, and non-releasing with a minimum unlocking strength of no less than 50 pounds and must be at least equivalent to an all-environment tolerant nylon cable tie.

Written Program

OSHA 29 CFR 1910.147 (c)(4) covers the minimal acceptable written program procedures. It must include:

  1. A specific written statement of the intended use of the procedure.
  2. Specific procedural steps are taken for shutting down, isolating, blocking and securing machines or equipment to control hazardous energy. This must be done for each piece of equipment, unless it is a duplicate.
  3. Specific procedural steps for the placement, removal and transfer of lockout devices and the responsibility for them.
  4. Specific requirements for testing the effectiveness of the lockout devices, tagout devices and other energy control measures.


Training of employees will be done by an authorized employee [29 CFR 1910.147 (c)(7)(I)]. The affected employees shall be instructed in the purpose and use of the energy control procedure and all other employees whose work operations are or may be in an area where energy control procedures may be utilized. When tagouts are used, employees must be instructed in the limitations of these devices.

Employee retraining shall be provided for all authorized and affected employees whenever there is a change in their job assignments, a change in machines, equipment or processes that present a new hazard, or when there is a change in the energy control procedures. After January 2, 1990, whenever replacement or major modification of a machine or equipment is performed, and whenever new machines or equipment are installed, energy isolating devices for such machines or equipment shall be designed to accept a lockout device. [29 CFR 1910.147 (c)(2)(iii)]

Removal of Lockout/Tagout Devices

Before lockout or tagout devices are removed, the authorized employee shall ensure that non-essential items are removed and machine components are operationally intact. The area should be checked to ensure all employees are safely positioned or removed and all affected employees notified that lockout/tagout devices have been removed. The lockout/tagout device must be removed by the person who applied the device. If the person who applied the device is not available, the device may be removed by another employee if the employer has established a specific procedure and training for this. When group lockout/tagout devices are used, a procedure equivalent to the personal lockout/tagout system should be followed. [(29 CFR 1910.147 (f)(3)]

Commonly Asked Questions

Q. Can I use a tagout instead of a lockout when it is impossible to lock out?
A. When it is impossible to lock out, or in industries where the use of tags has been well established and accepted as a recognized prohibitive to the operation of energy isolating devices, a tagout procedure has proven to be equal in protection to a lockout procedure.
Q. Do I have to lockout/tagout a machine that only requires the unit to be unplugged?
A. In situations where work on cord-and-plug-connected electric equipment is under the exclusive control of the employee performing the servicing or maintenance, the standard does not apply.
Q. Are there any other standards related to lockout/tagout?
A. Yes. OSHA can use 29 CFR 1910.212, General Requirements for All Machines, and 29 CFR 1910.219, Mechanical Power Transmission Apparatus, to cite business for lack of compliance. These two other areas allow OSHA to issue a double citation for non-compliance.

Product Reference:

Lab Safety Supply has the products you need to keep your workers safe and comply with current regulations. Please refer to the Lockout/Tagout and Training sections of your Lab Safety Supply General Catalog for details.

Sources for More Information

29 CFR 1910.1471910.212 and 1910.219.

ANSI Z244.1-2003, Personal Protection Lockout/Tagout of Energy Sources.

American National Standards Institute (ANSI)
11 W. 42nd St.
New York, NY 10036
(212) 642-4900

Seim, B., Beutler, W., “Ancillary Safety Interlocks Enhance Conventional Lockout/Tagout Procedures,” Occupational Health and Safety, October 1993, pp. 47–50.

Occupational Safety and Health Reporter, January 13, 1994, p. 973.


Affected employee. An employee whose job requires him/her to operate or use a machine or equipment on which servicing or maintenance is being performed under lockout or tagout, or whose job requires him/her to work in an area in which such servicing or maintenance is being performed.

Authorized employee. A person who locks out or tags out machines or equipment in order to perform servicing or maintenance on that machine or equipment. An affected employee becomes an authorized employee when that employee’s duties include performing servicing or maintenance covered under this section.

Capable of being locked out. An energy isolating device is capable of being locked out if it has a hasp or other means of attachment to which, or through which, a lock can be affixed, or it has a locking mechanism built into it. Other energy isolating devices are capable of being locked out, if lockout can be achieved without the need to dismantle, rebuild, or replace the energy isolating device or permanently alter its energy control capability.

Energized. Connected to an energy source or containing residual or stored energy.

Energy isolating device. A mechanical device that physically prevents the transmission or release of energy, including but not limited to the following: A manually operated electrical circuit breaker; a disconnect switch; a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors, and, in addition, no pole can be operated independently; a line valve; a block; and any similar device used to block or isolate energy. Push buttons, selector switches and other control circuit type devices are not energy isolating devices.

Energy source. Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy.

Hot tap. A procedure used in the repair, maintenance and services activities which involves welding on a piece of equipment (pipelines, vessels or tanks) under pressure, in order to install connections or appurtenances. it is commonly used to replace or add sections of pipeline without the interruption of service for air, gas, water, steam, and petrochemical distribution systems.

Lockout. The placement of a lockout device on an energy isolating device, in accordance with an established procedure, ensuring that the energy isolating device and the equipment being controlled cannot be operated until the lockout device is removed.

Lockout device. A device that utilizes a positive means such as a lock, either key or combination type, to hold an energy isolating device in the safe position and prevent the energizing of a machine or equipment. Included are blank flanges and bolted slip blinds.

Normal production operations. The utilization of a machine or equipment to perform its intended production function.

Servicing and/or maintenance. Workplace activities such as constructing, installing, setting up, adjusting, inspecting, modifying, and maintaining and/or servicing machines or equipment. These activities include lubrication, cleaning or unjamming of machines or equipment and making adjustments or tool changes, where the employee may be exposed to the unexpected energization or startup of the equipment or release of hazardous energy.

Setting up. Any work performed to prepare a machine or equipment to perform its normal production operation.

Tagout. The placement of a tagout device on an energy isolating device, in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.

Tagout device. A prominent warning device, such as a tag and a means of attachment, which can be securely fastened to an energy isolating device in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.

Mechanical Advantage

mechanical advantage 3 1




mechanical advantage complex

Confined Space Definitions

Acceptable entry conditions
(a)  the conditions that must exist in a permit space to allow entry and to ensure that employees involved with a permit-required confined space entry can safely enter into and work within the space.

an individual stationed outside one or more permit spaces who monitors the authorized entrants and who performs all attendant’s duties assigned in the employer’s permit space program.
Authorized entrant
an employee who is authorized by the employer to enter a permit space.
Blanking or blinding
the absolute closure of a pipe, line, or duct by the fastening of a solid plate (such as a spectacle blind or a skillet blind) that completely covers the bore and that is capable of withstanding the maximum pressure of the pipe, line, or duct with no leakage beyond the plate.
Confined space  
(1) Is large enough and so configured that an employee can bodily enter and perform assigned work; and
(2) Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins,
 hoppers, vaults, and pits are spaces that may have limited means of entry.); and
(3) Is not designed for continuous employee occupancy.
Double block and bleed
the closure of a line, duct, or pipe by closing and locking or tagging two in-line valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves.
any occurrence (including any failure of hazard control or monitoring equipment) or event internal or external to the permit space that could endanger entrants.
the surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance that can be aspirated to cause death by filling or plugging the respiratory system or that can exert enough force on the body to cause death by strangulation, constriction, or crushing.
the action by which a person passes through an opening into a permit-required confined space. Entry includes ensuing work activities in that space and is considered to have occurred as soon as  any part of the entrant’s body breaks the plane of an opening into the space.
Entry permit (permit)

the written or printed document that is provided by the employer to allow and control entry into a permit space and that contains the information specified in subsection (f).

Entry supervisor
the person (such as the employer, foreman, or crew chief) responsible for determining if acceptable entry conditions are present at a permit space where entry is planned, for authorizing entry and overseeing entry operations, and for terminating entry as required by this section.
Note: An entry supervisor also may serve as an attendant or as an authorized entrant, as long as that person is trained and equipped as required by this section for each role he or she fills. Also, the duties of entry supervisor may be passed from one individual to another during the course of an entry operation.
Hazardous atmosphere
an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space), injury, or acute illness from one or more of the following causes:
(1) Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL);
(2) Airborne combustible dust at a concentration that meets or exceeds its LFL;
Note: This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet (1.52 M) or less.
(3) Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;
(4) Atmospheric concentration of any substance for which a dose is published in Group 14 for Radiation and Radioactivity or a permissible exposure limit is published in section 5155 for Airborne  contaminants and which could result in employee exposure in excess of its dose or permissible exposure limit;
Note: An atmospheric concentration of any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects is not covered by this provision.
(5) Any other atmospheric condition that is immediately dangerous to life or health.
Note: For air contaminants for which a dose is not published in Group 14 for Radiation and Radioactivity or a permissible exposure limit is not published in section 5155 for Airborne contaminants, other sources of information such as: Material Safety Data Sheets that comply with section 5194, published information, and internal documents can provide guidance in establishing acceptable atmospheric conditions.
Hot work permit
the employer’s written authorization to perform operations (for example, riveting, welding, cutting, burning, and heating) capable of providing a source of ignition.
Immediately dangerous to life or health (IDLH)
any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual’s ability to escape unaided from a permit space.
Note: Some materials — hydrogen fluoride gas and cadmium vapor, for example — may produce immediate transient effects that, even if severe, may pass without medical attention, but are followed by sudden, possibly fatal collapse 12-72 hours after exposure. The victim “feels normal” from recovery from transient effects until collapse. Such materials in hazardous quantities are considered to be “immediately” dangerous to life or health.
the displacement of the atmosphere in a permit space by a noncombustible gas (such as nitrogen) to such an extent that the resulting atmosphere is noncombustible.
Note: This procedure produces an IDLH oxygen-deficient atmosphere.
the process by which a permit space is removed from service and completely protected against the release of energy and material into the space by such means as: Blanking or blinding; misaligning or removing sections of lines, pipes, or ducts; a double block and bleed system; lockout or tagout of all sources of energy; or blocking or disconnecting all mechanical linkages.
Line breaking
the intentional opening of a pipe, line, or duct that is or has been carrying flammable, corrosive, or toxic material, an inert gas, or any fluid at a volume, pressure or temperature capable of causing injury.
Non-permit confined space
a confined space that does not contain or, with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm.
Oxygen deficient atmosphere
an atmosphere containing less than 19.5 percent oxygen by volume.
Oxygen enriched atmosphere
an atmosphere containing more than 23.5 percent oxygen by volume.
Permit-required confined space (permit space)
a confined space that has one or more of the following characteristics:
(1) Contains or has a potential to contain a hazardous atmosphere;
(2) Contains a material that has the potential for engulfing an entrant;
(3) Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly
converging walls or by a floor which slopes downward and tapers to a smaller cross-section; or
(4) Contains any other recognized serious safety or health hazard.
Permit-required confined space program (permit space program)
the employer’s overall program for controlling, and, where appropriate, for protecting employees from, permit space hazards and for regulating employee entry into permit spaces.
Permit system
the employer’s written procedure for preparing and issuing permits for entry and for returning the permit space to service following termination of entry.
Prohibited condition
any condition in a permit space that is not allowed by the permit during the period when entry is authorized.
Rescue service
the personnel designated to rescue employees from permit spaces.
Retrieval system
the equipment (including a retrieval line, chest or full-body harness, wristlets, if appropriate, and a lifting device or anchor) used for non-entry rescue of persons from permit spaces.
the process by which the hazards that may confront entrants of a permit space are identified and evaluated. Testing includes specifying the tests that are to be performed in the permit space. If electronic or thermal equipment is used to perform such tests, and the possibility exists of an explosive substance or a hazardous atmosphere due to flammable gases and vapors, then the testing equipment must be approved for use in such explosive or flammable conditions as required by section 2540.2.
Note: Testing enables employers both to devise and implement adequate control measures for the protection of authorized entrants and to determine if acceptable entry conditions are present immediately prior to, and during, entry.


|                             |
| Does the workplace contain  |
| Confined Spaces as defined  NO ----------------------
|     by Section 5157(b)?     |                       |
|                             |                       |
|___________ YES _____________|                       |
              |                                       |
              |                                       |

 ____________ V ______________                        |
|                             |             _________ V ______
| Does the workplace contain  |            |                  |
|  Permit-required Confined   |            |  Consult other   |
|   Spaces as defined by      NO --------- >   applicable     |
|   Section 5157(b)?          |            |  OSHA standards. |
|                             |            |                  |
|___________ YES _____________|            |_____ STOP _______|
     ________ V ___________
    |                      |
    | Inform employees as  |
    |     required by      |
    | Section 5157(c)(2).  |
    |                      |      _____________________________
    |______________________|     |                             |
              |                  | Prevent employees entry as  |
     ________ V ___________      | required by Section 5157    |
    |                      |     |  (c)(3). Do task from       |
    |  Will permit         NO -- >     outside of space.       |
    | spaces be entered?   |     |_____________________________|
    |                      |
    |_______ YES __________|
     ________ V _______         ________________________________
    |                  |       |                                |
    | Will contractors |       |     Task will be done by       |

 -- >     enter?       YES --- > contractors' employees. Inform |
|   |                  |       |  contractor as requited by     |
|   |________ NO ______|       | Section 5157(c)(8)(i), (ii)    |
|              |               | and (iii). Contractor obtains  |
|              |               |   information required by      |
|              |               | Section 5157(c)(9)(i), (ii)    |
|              |               |   and (iii) from host.         |
|              |               |________________________________|
|              |                           |
|              |               ___________ V ___________________
|              |              |                                 |
|              |              |   Both contractors and host     |
|              |              | employees will enter the space? NO >
|              |              |                                 |   |
|              |              |_______ YES _____________________|   |
|              |                        |                           |
|  ___________ V _______   ____________ V _______________________   |
| |                     | |                                      |  |
| | Will host employees | |   Coordinate entry operations as     |  |
| |  enter to perform   | |required by Section 5157(c)(8)(iv) and|->|
| |    entry tasks?     | | (d)(11).Prevent unauthorized entry   |  |
| |                     | |______________________________________|  |
| |____ YES ________NO _|                                           |
|        |           |     ______________________________           |
|        |           |    |                              |          |
|        |           ----->  Prevent unauthorized entry. STOP       |
|        |                |______________________________|          |
|        |                                                          |
|        |<---------------------------------------------------------
|        |
|  _____ V ________________     _________________________________
| |                        |   |                                 |
| | Does space have known  |   | Not a permit-required confined  |
| | or potential hazards?  NO--> space. 5157 does not apply. |
| |                        |   | Consult other OSHA standards.   |
| |______ YES _____________|   |_________________________________|
|          |
|          |                     _________________________
|  _______ V_____________       |                         |
| |                      |      | Employer may choose to  |
| |  Can the hazards be  YES----> reclassify space to     |
| |     eliminated?      |      | non-permit required     STOP(1)
| |                      |      | confined space using    |
| |_______ NO ___________|      |    Section 5157(c)(7).  |
|           |                   |_________________________|
|           |
|  ________ V ___________________
| |                              |      __________________
| | Can the space be maintained  |     |                  |
| | in a condition safe to       YES--->  Space may be    |
| | enter by continuous forced   |     |  entered under   STOP(1)
| |   air ventilation only?      |     | 5157(c)(5).      |
| |                              |     |__________________|
| |_______ NO ___________________|
|           |
|           |
|  ________ V ______________
| |                         |
| | Prepare for entry via   |
| |   permit procedures.    |
| |_________________________|
|           |
|           |                      ____________________
|  ________ V ________________    |                    |
| |                           |   | Permit not valid   |
| | Verify acceptable entry   NO--> until conditions   |
| | conditions (test results  |   |  meet permit       |
| | recorded, space isolated  |   | specifications.    |
| | if needed, rescuers/means |   |____________________|
| |   to summon available,    |
| |    entrants properly      |
| |     equipped, etc.)       |
| |                           |
| |_______ YES _______________|
|           |
|           |
|  ________ V ___________________      ______________________________
| |                              |    |                              |
| | Permit issued by authorizing |    | Emergency exists (prohibited |
| | signature. Acceptable entry  NO--->    condition). Entrants      |
| |   conditions maintained      |    |   evacuated entry aborts.    |
| |    throughout entry.         |    |  (Call rescuers if needed).  |
| |                              |    |  Permit is void. Reevaluate  |
| |________ YES _________________|    |  program to correct/prevent  |
|            |                        |     prohibited condition.    |
|            |                        |    Occurrence of emergency   |
|  _________ V ___________________    |    (usually) is proof of     |
| |                               |   |    deficient program. No     |
| |   Entry tasks completed.      |   |    re-entry until program    |
| | Permit returned and canceled. |   |   (and permit) is amended.   |
| |_______________________________|   |  (May require new program.)  |
|            |                        |                              |
|            |                        |____ CONTINUE ________________|
|  _________ V _____________________           |
| |                                 |          |
| | Audit permit program and permit |          |
| | based on evaluation of entry by |          |
| |  entrants, attendants, testers  |          |
| |       and preparers, etc.       |          |
| |_________________________________|          |
|                                              |
(1) Spaces may have to be evacuated and re-evaluated if hazards arise during entry.