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OSHA term · Glossary

Hazardous Energy

Verified vs OSHA sources · 2026-10-05

Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy in machines or equipment that can cause injury during servicing or maintenance if released unexpectedly. Under OSHA's Control of Hazardous Energy standard (29 CFR 1910.147, 'Lockout/Tagout'), equipment is 'energized' when connected to an energy source OR when it contains residual or stored energy. The standard requires that all such energy be isolated, locked out or tagged out, and verified as controlled before an authorized employee begins work.

29 CFR 1910.14729 CFR 1910.147(b)

Also known as: stored energy, unexpected energization, residual energy

Hazardous Energy at a glance

  • Forms of hazardous energy: electrical, mechanical, hydraulic, pneumatic, chemical, thermal — plus gravitational and stored/residual energy.
  • 'Energized' includes residual or stored energy — not just live connection to a power source.
  • Covers servicing and maintenance, NOT normal production operations (with limited exceptions where guards must be removed or body parts enter the danger zone).
  • The 6-step energy control procedure: prepare → shut down → isolate → apply lockout/tagout → release stored energy → verify isolation.
  • Verification (1910.147(d)(6)) is mandatory before work begins — the authorized employee must confirm de-energization.
  • Periodic inspection of the energy control procedure is required at least annually, by an authorized employee not using the procedure being inspected.
  • The hazardous energy standard (1910.147) ranked fourth on OSHA's FY2025 list of most-cited standards, and unexpected start-up during servicing causes amputations and machine-related deaths.

In plain English

The dangerous energy trapped inside machines — electricity, pressure, springs, heat, gravity-loaded parts. If a machine unexpectedly starts up or discharges stored energy while someone is repairing it, the result can be amputation or death. OSHA's lockout/tagout rules require every energy source to be shut off, locked, and verified dead before hands go inside.

What the rule says

“Energized. Connected to an energy source or containing residual or stored energy. … Energy source. Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy.”
29 CFR 1910.147(b) — 'Energized'

In context

An enforcement, recordkeeping, or general-duty concept under the Occupational Safety and Health Act and 29 CFR. These terms define how OSHA inspects, cites, and penalizes employers.

29 CFR Chapter XVII

Where this is written in OSHA's rules

Example

A maintenance technician must clear a jam in a hydraulic press. The press has three energy sources: 480V electrical, a hydraulic accumulator holding pressure, and a gravity-loaded ram. Controlling hazardous energy means: opening and locking the electrical disconnect, bleeding the hydraulic accumulator to zero pressure, blocking the ram so it cannot fall, and then verifying (by trying the start button and gauging pressure) that all energy is at zero before reaching in. Locking only the electrical source would leave the stored hydraulic and gravitational energy uncontrolled — a fatal gap.

Why it matters

Uncontrolled hazardous energy is a leading cause of workplace amputations, crushing injuries, and deaths during machine servicing. OSHA estimates that compliance with the Lockout/Tagout standard prevents tens of thousands of injuries each year. Because 'energized' includes stored and residual energy, workers who lock out only the electrical supply — and overlook trapped hydraulic pressure, compressed springs, or gravity-loaded components — remain exposed to the exact hazard the standard is designed to eliminate.

Hazardous energy is more than electricity

Many workers equate 'lockout/tagout' with 'shut off the power.' But electrical energy is only one of the forms OSHA lists. Compressed air, hydraulic pressure, a raised load held by gravity, steam or hot fluid, and a wound spring are all hazardous energy — and each must be separately isolated and its stored energy released. A machine can be fully disconnected from electricity and still contain lethal stored energy. This is why 1910.147(d)(5) requires relieving, disconnecting, or restraining ALL stored or residual energy.

Forms of Hazardous Energy & How Each Is Controlled

Energy FormExample SourceControl Method
ElectricalMotors, live circuits, capacitorsOpen + lock disconnect; discharge capacitors
Mechanical (stored)Springs, flywheels, tensioned beltsBlock, restrain, or release tension
HydraulicAccumulators, pressurized linesBleed pressure to zero; lock valves
PneumaticCompressed-air systemsIsolate + bleed to zero pressure
GravitationalRaised loads, suspended ramsBlock, pin, or lower to rest
Thermal / ChemicalSteam, hot fluids, process chemicalsIsolate, drain, cool, purge

Hazardous Energy: frequently asked questions

Does hazardous energy include stored energy, or only live power?
It includes both. Under 29 CFR 1910.147(b), equipment is 'energized' when it is connected to an energy source OR when it contains residual or stored energy. Compressed springs, hydraulic accumulators, raised loads, capacitors, and pressurized systems all hold hazardous energy even after the power is disconnected. Step 5 of the energy control procedure specifically requires that all stored or residual energy be relieved, disconnected, or restrained.
When does the Lockout/Tagout standard apply?
1910.147 applies to servicing and maintenance of machines and equipment where the unexpected energization, start-up, or release of stored energy could injure employees. It does NOT apply to normal production operations, except where an employee must remove or bypass a guard or place a body part into a point-of-operation or danger zone during the operation — in which case the servicing exception is triggered and lockout/tagout applies.
How often must the energy control procedure be inspected?
At least annually. Under 1910.147(c)(6), the employer must conduct a periodic inspection of each energy control procedure at least once a year, performed by an authorized employee other than the one(s) using the procedure being inspected. The inspection must verify that employees understand and follow the procedure, and any deviations must be corrected.

Related terms

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More OSHA terms

Abatement

The action an employer takes to fix a cited violation or eliminate a hazard OSHA identified during an inspection. The citation sets an abatement date, the deadline to correct the hazard, and within 10 calendar days after that date the employer must certify to OSHA that the violation was abated. Failure to abate accrues additional penalties of up to $16,550 per day.

Area Director

The senior OSHA official in charge of a specific OSHA Area Office — the local unit that runs inspections and enforcement in its geographic territory. The Area Director has the authority to issue citations, propose penalties, hold informal conferences with employers, and approve settlement agreements. When a Compliance Safety and Health Officer (CSHO) completes an inspection, it's the Area Director who ultimately issues the citation.

Bureau of Labor Statistics (BLS)

The federal statistical agency within the U.S. Department of Labor that collects, analyzes, and publishes data on workplace injuries, illnesses, and fatalities. BLS conducts the annual Survey of Occupational Injuries and Illnesses (SOII) — compiled from employer OSHA 300 logs — and the Census of Fatal Occupational Injuries (CFOI). SOII data drives OSHA's Site-Specific Targeting (SST) program: establishments whose DART rates significantly exceed their BLS industry average are placed on the SST inspection list.

Competent Person

Under OSHA's construction standards, a person who is capable of identifying existing and predictable hazards in the surroundings or working conditions, and who has the authorization to take prompt corrective measures to eliminate them. The role requires both knowledge and the authority to act, and is mandated by name in many specific standards — excavations, scaffolds, fall protection, asbestos, and more.

Citation

The formal written notice OSHA issues to an employer after an inspection, describing each alleged violation, the standard cited, the proposed penalty, and the date by which the hazard must be corrected (abated). OSHA must issue a citation with reasonable promptness and no later than six months after the violation occurred.

Closing Conference

The meeting at the end of an OSHA inspection where the compliance officer confers with the employer and informally advises them of any apparent violations found. Importantly, the closing conference discusses what was observed and the employer's rights — but it does NOT state final citations or penalties, which come later in the written Citation and Notification of Penalty.

Compliance Officer (CSHO)

An OSHA Compliance Safety and Health Officer — the inspector who conducts workplace inspections. A CSHO presents credentials (a photo ID and a serial number), holds the opening conference, performs the walkaround, collects evidence, interviews employees, and recommends citations. CSHOs are either safety specialists or industrial hygienists.

Contest

An employer's formal challenge to an OSHA citation, penalty, or abatement date. To contest, the employer must file a written Notice of Contest with the OSHA Area Director within 15 working days of receiving the Citation and Notification of Penalty. Filing sends the case to the independent Occupational Safety and Health Review Commission (OSHRC); missing the deadline makes the citation a final, un-appealable order.

Sources & verification

Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.

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