OSHA term · Glossary
Zero Energy State
Verified vs OSHA sources · 2026-10-05
The verified condition in which all energy sources to a machine or piece of equipment — electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and gravitational — have been isolated, locked out or tagged out, and confirmed to hold no residual or stored energy. Achieving and verifying a zero energy state is the objective of the 29 CFR 1910.147 energy control procedure: the authorized employee must verify isolation and de-energization (1910.147(d)(6)) before any servicing or maintenance begins.
Also known as: zero-energy verification, de-energized state, verification of isolation
On this page
Zero Energy State at a glance
- Zero energy state = ALL energy forms isolated AND verified — not just the electrical supply.
- Verification (1910.147(d)(6)) is a mandatory, separate step performed BEFORE work begins.
- Common verification methods: attempt to start the machine (then return the control to off/neutral), test with a voltage meter, and read pressure gauges to confirm zero.
- Stored energy (springs, accumulators, capacitors, raised loads) must be released or restrained to reach zero energy — locking the disconnect alone does not achieve it.
- The 'try' step of Lock-Tag-Try refers directly to verifying the zero energy state.
- If any energy source cannot be reduced to zero (e.g., a load that cannot be lowered), it must be physically blocked or restrained and treated as a continuing hazard.
In plain English
The point at which a machine is provably 'dead' — no electricity, no pressure, no trapped spring or raised weight — and someone has actually confirmed it, not just assumed it. It is the last box to check before hands go in. The word 'verified' is key: locking a switch is not enough until you test that the energy is truly gone.
What the rule says
“Prior to starting work on machines or equipment that have been locked out or tagged out, the authorized employee shall verify that isolation and deenergization of the machine or equipment have been accomplished.”
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.
Where this is written in OSHA's rules
- 29 CFR 1910.147(d)(6)Read on eCFR / OSHA.gov
- 29 CFR 1910.147Read on eCFR / OSHA.gov
Example
After isolating a conveyor's 480V supply and locking the disconnect, an authorized employee verifies the zero energy state by: (1) pressing the start button at the operator station — the conveyor does not move; (2) confirming with a voltage meter that the motor terminals read zero; and (3) verifying that the gravity take-up weight is pinned so it cannot drop. Only when all three checks confirm no energy remains is the zero energy state established and servicing permitted.
Why it matters
Skipping or faking verification is one of the most dangerous shortcuts in machine servicing. Workers have been killed because a machine was 'locked out' but never verified — a mislabeled disconnect, a second unknown power feed, or trapped hydraulic pressure remained live. The zero energy state, confirmed by an affirmative test, is the difference between a machine that is assumed safe and one that is proven safe. OSHA cites the missing verification step frequently in fatality investigations.
Locked out ≠ zero energy state
Applying a lock to an energy-isolating device is a necessary step, but it does not by itself establish a zero energy state. A disconnect can be locked while a second power feed, a charged capacitor, trapped pneumatic pressure, or a gravity-loaded component still holds lethal energy. The zero energy state is reached only after stored energy is released or restrained AND the absence of energy is affirmatively verified — by test, by gauge, or by attempting to operate the equipment. 'Locked out' is an action; 'zero energy state' is a verified result.
Reaching a Verified Zero Energy State
| Step | Action | How Zero Is Confirmed |
|---|---|---|
| Isolate | Open + lock each energy-isolating device | Device physically locked in the safe/off position |
| Release stored energy | Bleed, block, restrain, or discharge | Gauges at zero; loads blocked; capacitors discharged |
| Verify (the 'Try') | Attempt to operate; test with instruments | Machine won't start; meter/gauge reads zero |
Zero Energy State: frequently asked questions
- What does it mean to verify a zero energy state?
- Verification means affirmatively confirming — not assuming — that no energy remains. Under 1910.147(d)(6), before starting work the authorized employee must verify that isolation and de-energization have been accomplished. Typical methods include attempting to start the equipment (then returning the control to off), using a voltage meter to confirm zero voltage, and checking pressure gauges. Verification is a required step, not an optional best practice.
- Is locking the disconnect enough to reach a zero energy state?
- No. Locking the energy-isolating device isolates the primary source but does not address stored or residual energy — hydraulic pressure, compressed springs, charged capacitors, raised loads, or a second unknown power feed can remain. To reach a zero energy state, all stored energy must be released or restrained, and then the de-energized condition must be verified by test. Only then is the machine proven safe to service.
- What if an energy source cannot be reduced to zero?
- Some energy cannot be fully eliminated — for example, a heavy component that cannot be lowered, or a system that must retain some pressure. In those cases the energy must be physically blocked, pinned, or restrained so it cannot be released unexpectedly, and the residual hazard must be identified in the energy control procedure and communicated to the servicing employee. The goal remains preventing unexpected release, even where absolute zero is not achievable.
Related terms
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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 DirectorThe 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 PersonUnder 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.
CitationThe 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 ConferenceThe 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.
ContestAn 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
- 29 CFR 1910.147(d)(6) (eCFR / OSHA.gov)
- 29 CFR 1910.147 (eCFR / OSHA.gov)
- OSHA — 29 CFR 1910.147 (Control of Hazardous Energy)
- OSHA — Lockout/Tagout (Safety and Health Topics)
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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