Lockout/Tagout Procedures — Toolbox Talk Guide

Recognizing Hazardous Energy Sources

Hazardous energy takes many forms, and a thorough energy source identification is the first step of any LOTO procedure. Electrical energy is the most recognized source — motors, control circuits, capacitors, and battery backup systems all store or conduct lethal current. But equipment also stores hydraulic energy in pressurized lines and cylinders, pneumatic energy in air receivers and actuators, mechanical energy in compressed springs and flywheels, thermal energy in steam lines and heated surfaces, and gravitational potential energy in elevated components or suspended loads. Under 1910.147(c)(4)(i), employers must document all energy sources for each piece of covered equipment in a machine-specific energy control procedure.

Stored and residual energy is the category most frequently overlooked during LOTO execution. Turning off and locking out the main electrical disconnect does not discharge capacitor banks, which can retain lethal voltage for minutes or hours after power removal. Closing an upstream hydraulic shutoff valve does not bleed pressure downstream of the valve. Locking out a pneumatic supply does not exhaust pressure in actuators or accumulator tanks. Elevated machine components supported only by hydraulic pressure will descend when that pressure is released. Each energy source must be identified, isolated, and verified as fully released before the equipment is considered safe to touch.

The Six-Step LOTO Procedure

OSHA 1910.147(d) establishes the sequence for applying energy controls. Step 1 — Prepare for shutdown: identify all energy sources, review the machine-specific energy control procedure, and notify affected employees that servicing is beginning. Step 2 — Shut down the equipment: use the normal stopping procedure; do not attempt to isolate energy while the machine is running if a safe shutdown sequence exists. Step 3 — Isolate all energy sources: operate each isolating device — circuit breakers, disconnect switches, valves, and mechanical blocks — to the off, closed, or blocked position.

Step 4 — Apply lockout or tagout devices: each authorized employee applies their personal lock to every isolation point. Under 1910.147(c)(1), whenever replacement or repair of parts exposes employees to the unexpected energization of machines or equipment, lockout devices shall be used. Tagout is only permissible when the equipment cannot be locked out and the employer can demonstrate that the tagout program provides equivalent employee protection. Tagout alone — a tag without a lock — provides no physical barrier to re-energization and is prohibited where lockout is feasible. Step 5 — Release or restrain stored energy: bleed pneumatic lines, relieve hydraulic pressure, discharge capacitors, block elevated components, and allow thermal energy to dissipate. Step 6 — Verify isolation: attempt to operate the equipment using its normal start controls. Test for voltage with a properly rated meter. Confirm that no unexpected motion occurs before beginning work.

The verify step is non-negotiable and cannot be skipped in the interest of time. Attempting to start the machine confirms that the control circuit is isolated. Using a voltmeter at the load terminals confirms electrical de-energization beyond the disconnect. Physical blocks and pins confirm that gravitational and spring energy has been restrained. The cost of verification is seconds; the cost of skipping it can be life-altering. Many LOTO fatalities occur on equipment that was believed to be isolated because a worker relied on observation rather than testing.

Authorized vs. Affected Employees

OSHA 1910.147 distinguishes between three employee categories with different roles and responsibilities. Authorized employees are trained workers who have the knowledge and authority to apply and remove LOTO devices — they perform the servicing or maintenance work and own their personal locks. Affected employees are workers who operate or use the machine being serviced, or who work in an area where servicing is being performed. They must understand why the equipment is locked out and must never attempt to restart it or remove another person's lock. Other employees are anyone else in the area who must be informed of LOTO activities and the prohibition against interfering with lockout devices.

The distinction between authorized and affected is not just semantic — it carries legal and safety significance. Only an authorized employee who applied a lockout device may remove it, with one narrow exception under 1910.147(e)(3): when the authorized employee who applied the lock is unavailable, the employer may establish a documented procedure for removal by another authorized employee, which requires verification that the original authorized employee is not on site and notification to that employee before they return. Removing another worker's lock without this procedure is prohibited and has caused fatalities when the original authorized employee returned to work on what they believed was still an isolated machine.

Group Lockout and Complex Multi-Energy Procedures

Group lockout is required when servicing or maintenance is performed by a crew, rather than a single authorized employee. Under 1910.147(f)(3), when a group is working under one energy control procedure, each individual authorized employee in the group must apply their own personal lock to a group lockout hasp or box. A single supervisor lock does not provide individual protection — if the supervisor is called away, completes their work, or otherwise removes their lock, all workers in the group lose their individual protection unless each has their own lock on the isolation point.

Complex equipment with multiple energy sources — assembly lines, large presses, HVAC systems, paper machines — requires a written energy control procedure that lists every isolation point in sequence. OSHA 1910.147(c)(4)(ii) allows an exception from written procedures only for equipment with a single energy source that can be completely de-energized and locked out by a single lockout device — a narrow exception that applies to very little production machinery. Multi-energy procedures must be followed in the exact sequence documented; skipping steps or assuming an isolation point is inactive based on past experience is the mechanism behind many energy-release incidents.

Contractor coordination is a significant LOTO challenge. Under 1910.147(f)(2), when outside contractors perform servicing on a host employer's equipment, the host and contractor must coordinate their energy control procedures to ensure equivalent protection. The host employer must inform the contractor of the site-specific energy control procedures; the contractor must comply with those procedures or demonstrate that their own program provides equivalent protection. Joint lockout operations must include hasp coordination so that both the host employer's and contractor's workers are independently protected.

Restoring Equipment to Service

The energy restoration sequence is as critical as the lockout sequence. Before removing LOTO devices and re-energizing equipment, the authorized employee must confirm that all work is complete, all tools and non-essential materials have been removed from the machine, all guards and safety devices have been reinstalled, all workers are clear of the equipment and at a safe distance, and all affected employees have been notified that energy will be restored. These steps must be completed in sequence — re-energization before guards are installed or before workers are confirmed clear has caused serious injuries.

After confirming all employees are clear, each authorized employee removes only their own lock from the isolation points in the reverse order of application. The machine operator — not the servicing crew — should perform the test start to confirm equipment function, which keeps the servicing crew in their proper role and ensures the operator understands any changes made during maintenance. Any abnormal condition discovered during the test start requires immediate shutdown and re-application of LOTO before investigation.

OSHA requires that all authorized employees under an energy control program receive training specific to the hazardous energy sources on the equipment they service, the means and methods of energy isolation, and the requirements of the energy control program. Retraining is required whenever there is reason to believe an employee lacks the required knowledge, whenever equipment or procedures change, or whenever periodic inspection reveals a deviation from the energy control procedure. Periodic inspections of the energy control program must occur at least annually per 1910.147(c)(6) and must be documented.

✅ Key Takeaways

• →LOTO covers all hazardous energy types — electrical, hydraulic, pneumatic, mechanical, thermal, chemical, and gravitational; identify every source before beginning.
• →Follow the six-step sequence: prepare, shut down, isolate, apply locks, release stored energy, and verify zero energy state by attempting to start and metering voltage.
• →Each authorized employee in a group lockout must apply their own personal lock to the hasp — a single supervisor lock does not protect individual crew members.
• →Only the authorized employee who applied a lock may remove it; removing another worker's lock requires a documented emergency removal procedure with mandatory notification.
• →Tagout alone (tag without a lock) is only permissible when the equipment cannot accept a lockout device and equivalent protection is demonstrated — it is prohibited wherever lockout is feasible.
• →Restore equipment in sequence: confirm work complete, guards reinstalled, all workers clear, affected employees notified — then each authorized employee removes only their own lock.

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