Controlling Hazardous Energy

To be safe, take it step by step

Controlling hazardous energy or lockout/tagout (LOTO) can be a complex subject for the electrical industry. Different regulations address it from all perspectives. There is the concept of whether the work is construction or maintenance and whether the lines are part of power transmission and distribution or basic installation. The Occupational Safety and Health Administration (OSHA) has four sets of regulations on electrical work which may or may not apply to a specific LOTO situation. To ensure complete coverage, OSHA created a general LOTO standard. It is separate from the guidelines for electrical safety found in both the Construction and General Industry Standards.

The various electrical standards reference the steps found in the general LOTO regulation (29 CFR 1910.147) as an option for compliance. The key to safety is identifying all energy sources and taking steps to control them.

Hazardous energy is any type of energy in sufficient quantity to cause injury to a worker. For the sake of LOTO, the National Institute of Occupational Safety and Health (NIOSH) classifies hazardous energy into four categories. They are kinetic energy, potential energy, electrical energy and thermal energy.

Kinetic energy involves the moving parts of mechanical systems. Workers are typically injured when a system is unexpectedly energized during a repair or maintenance operation. Injury results from contact with the moving parts. A simple example comes to mind from the television commercial produced for a do-it-yourself construction supply company where the husband installs a garbage disposal. Then his wife comes home and flips the light switch.

Potential energy is stored energy. It can be found in pressure vessels, hydraulic or pneumatic systems, and springs. It is difficult to detect without a thorough working knowledge of the equipment. For example, few electricians are probably aware that some tire and wheel assemblies use a split rim that is mechanically held under pressure. The simple act of taking the assembly apart can release stored energy, causing injury and death.

The hazardous energy most common to our industry is electrical. Employees must be protected from all equipment and lines carrying this energy source. OSHA mandates that work on parts of more than 50V be deenergized, unless this will create a greater hazard. Some sources of electrical energy may be hard to detect. Electricians must be aware of all components within a piece of equipment, such as capacitors and backup batteries. The presence of these components means stored electricity may remain after the power is cut off.

The final classification of hazardous energy is thermal. Thermal energy refers to temperature extremes. Heat can be created from mechanical work, chemical reactions or electrical resistance. Extreme heat results in burns, fires and explosions. Equally dangerous is extreme cold. Cryogenic systems can instantly freeze anything that is contacted. Frozen parts can remain at hazardous temperatures for extended periods.

Electrical workers may be exposed to hazardous energy in several forms and combinations in a single operation. It is not unusual to find electricity and pneumatic power used in a single piece of equipment.

Once the energy sources have been identified, it must be determined what methods will be used to control them. These procedures should be made available to employees as part of an energy control plan. The plan must include the following.

• Notification of all affected employees that servicing or maintenance is required on a line or equipment, and lockout will be performed.

• Ensuring reference to procedures established for that equipment regarding the type and magnitude of energy and the methods to control it.

• Shutting down the line or equipment.

• Activating the energy-isolating device(s) to isolate the energy source(s).

• Locking out the energy-isolating device. According to 1910.147, each employee working on the equipment must be assigned an individual lock.

• Dissipating stored or residual energy (such as that in capacitors, springs, elevated machine members, hydraulics and air, steam, or water pressure, etc.) by methods such as grounding, repositioning, blocking, bleeding down, etc.

• Verifying the isolation of equipment by operating push buttons or other normal controls, or by testing to make certain equipment will not operate.

These basic steps can provide the foundation for controlling hazardous energy. Additional precautions need to be implemented for releasing the lockout and dealing with special circumstances such as absentee workers. Employers must ensure that compliant energy control procedures are present, special circumstances are addressed and that workers have been effectively trained.

Other references should be consulted to help you meet all the requirements of LOTO. Recommended sources include the OSHA Web site (, NECA Safety Expert System Software, and EC

O’CONNOR is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or


About the Author

Joe O'Connor

Freelance Writer
Joe O'Connor is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or joconnor@inte...

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.