| Quick Answer: Lockout/tagout (LOTO) is the practice of isolating and de-energizing equipment during servicing and maintenance so it cannot start up or release stored energy unexpectedly. OSHA’s standard for the control of hazardous energy (29 CFR 1910.147) requires a written energy-control program, specific procedures, employee training, and periodic inspections. It is credited with preventing an estimated 120 deaths and 50,000 injuries every year. |
Most serious maintenance injuries are not caused by exotic failures — they are caused by equipment that started up, or released stored energy, while someone was working on it. Lockout/tagout exists to make that impossible. It is one of the most cited and most important safety programs in any facility, and getting it right protects maintenance workers from electrical, mechanical, hydraulic, and other hazardous energy every day.
What Lockout/Tagout Means
LOTO is a set of practices for placing equipment into a zero-energy state before servicing and keeping it there until the work is done. “Lockout” means applying a physical lock to an energy-isolating device so it cannot be operated. “Tagout” means attaching a warning tag where a lock cannot be used. The goal is the same in both cases: ensure that the machine cannot be energized or release stored energy while a worker is exposed. It applies far beyond electricity — to mechanical, hydraulic, pneumatic, chemical, and thermal energy as well.
What OSHA Requires
OSHA’s control of hazardous energy standard (29 CFR 1910.147) sets the minimum performance requirements. Employers must establish a written energy-control program, develop specific lockout procedures for equipment, provide locks and tags, train affected and authorized employees, and conduct periodic inspections of the program. The standard is built around the principle that servicing and maintenance — where unexpected energization could injure someone — must not proceed until hazardous energy is controlled. It is a performance standard, meaning the employer must achieve the outcome, not just file paperwork.
The Core Steps of a Lockout
A compliant lockout follows a consistent sequence. First, prepare for shutdown by identifying all energy sources for the equipment. Second, notify affected employees and shut the equipment down using its normal stopping procedure. Third, isolate the equipment by operating the energy-isolating devices — disconnects, valves, breakers. Fourth, apply locks and tags so those devices cannot be re-operated. Fifth, control or release stored energy: discharge capacitors, bleed pressure, block suspended parts, dissipate thermal energy. Sixth and most important, verify isolation by attempting to operate the controls and testing that the equipment is truly de-energized before any work begins. Only then is the equipment safe to service.
Lockout vs Tagout: Why Locks Win
OSHA prefers lockout over tagout because a lock physically prevents operation, while a tag is only a warning that someone could ignore or remove. Tagout alone is permitted only when the energy-isolating device cannot accept a lock, and even then the employer must demonstrate that the tagout program provides protection equivalent to lockout — which typically requires additional measures. In modern facilities, the right answer is usually to use lockable isolation devices so that a true lock can always be applied.
Where LOTO and Electrical Safety Meet
LOTO is the practical mechanism behind placing electrical equipment in an electrically safe work condition. De-energizing, locking out, and verifying dead is exactly how NFPA 70E expects qualified workers to eliminate the electrical hazard before work. The two frameworks reinforce each other: OSHA’s 1910.147 governs the control of hazardous energy broadly, while NFPA 70E details the electrical-specific safe work practices. Training that teaches both together — when a permit is needed, when a lockout is needed, and how they fit — produces workers who make the safe choice by reflex. Bowtie’s electrical safety training covers this intersection directly.
Periodic Inspections and Procedure Specificity
Two requirements trip up otherwise diligent facilities. First, OSHA requires equipment-specific written procedures — a single generic “lock it out” procedure does not satisfy the standard for machines with multiple or complex energy sources. Second, the program must be inspected at least annually by an authorized person other than the one using the procedure, to confirm it is being followed and is still adequate. These inspections are not box-checking; they are how a program stays current as equipment and personnel change. Folding LOTO procedure reviews into a broader electrical maintenance program keeps them from being forgotten.
Stored Energy: The Step People Skip
The most dangerous shortcut in any lockout is skipping the stored-energy step. Capacitors hold charge after disconnection; hydraulic and pneumatic systems hold pressure; springs and suspended loads hold mechanical energy; steam and process lines hold thermal energy. A lock on the disconnect does nothing about a charged capacitor bank. That is why the sequence demands discharging, bleeding, blocking, or relieving every stored-energy source and then verifying a zero-energy state. The verification step — actually testing that the equipment is dead — is the single most important action in the entire procedure.
Building a LOTO Program That Holds Up
A strong program starts with a complete equipment inventory and energy-source survey, then builds specific procedures for each machine, supplies the right locks and tags, and trains employees by role: authorized employees who perform lockouts, affected employees who operate the equipment, and others who work in the area. It documents annual inspections and updates procedures whenever equipment changes. Done well, LOTO becomes second nature rather than a binder on a shelf — and that habit is what actually prevents the unexpected start-up that the standard exists to stop.
A particular hazard worth calling out is group and shift-change lockout. When several workers service the same equipment, each must apply their own lock, so the equipment cannot be re-energized until the last person removes theirs; a group lockbox is the usual mechanism. Shift changes are a classic failure point, because the protection must transfer without ever leaving the equipment unlocked. Establishing clear rules for group lockout, shift handover, and the removal of another worker’s lock — which should happen only through a documented, exceptional procedure — closes the gaps where real incidents tend to occur.
Frequently Asked Questions
What OSHA standard governs lockout/tagout?
29 CFR 1910.147, the control of hazardous energy, for general industry.
What are the basic LOTO steps?
Prepare, shut down, isolate, apply locks/tags, control stored energy, and verify a zero-energy state before working.
Is tagout alone acceptable?
Only when a device cannot accept a lock, and only if the program provides protection equivalent to lockout.
How often must the program be inspected?
At least annually, by an authorized person other than the one using the procedure.
Does LOTO cover more than electricity?
Yes — electrical, mechanical, hydraulic, pneumatic, chemical, and thermal energy.
Key Takeaways
- LOTO isolates and de-energizes equipment so it cannot start up or release stored energy during service.
- OSHA 1910.147 requires a written program, equipment-specific procedures, training, and annual inspections.
- Verifying a true zero-energy state — and controlling stored energy — is the most critical step.
- LOTO is how electrical equipment reaches an electrically safe work condition under NFPA 70E.