A maintenance technician is called to clear a jam in a conveyor system. He reaches into the machine without first locking it out. A co-worker on the other side of the facility, unaware anyone is in the machine, restarts the line.
The technician loses two fingers.
This type of incident is documented in OSHA’s severe injury reporting database dozens of times each year. The cause is almost always the same: energy was not controlled before work began. The prevention is almost always the same too: lockout/tagout, applied correctly, every time.
Lockout/tagout violations are among the top five most frequently cited OSHA standards in general industry year after year. OSHA estimates that compliance with the lockout/tagout standard (29 CFR 1910.147) prevents approximately 50,000 injuries and 120 fatalities annually. The injuries that do occur happen almost exclusively when the procedure is skipped, abbreviated, or improperly applied.
What Lockout/Tagout Is and Why It Exists
Lockout/tagout is a safety procedure that ensures machines and equipment are properly shut off and cannot be re-energised until maintenance or service work is complete. It is governed by OSHA 29 CFR 1910.147 for general industry and 29 CFR 1926.417 for construction. Electrical work specifically is also covered under 29 CFR 1910.333.
The hazard it addresses is stored energy. Machines that appear to be off can still contain hazardous energy in the form of electrical charge, compressed air, hydraulic pressure, gravity, spring tension, or thermal energy. If that energy releases unexpectedly while a worker is in contact with the machine, the results can include crush injuries, amputations, electrocution, and death.
Lockout means physically attaching a lock to an energy isolating device, such as a circuit breaker or a valve, so the device cannot be operated. Tagout means attaching a tag to warn others that the equipment must not be operated. Where the energy isolating device cannot be locked, tagout is used as an alternative with additional safeguards.
Electricity is the most commonly encountered stored energy hazard in lockout/tagout situations. Unlike hydraulic pressure or spring tension, electrical energy is invisible, silent, and can be present even when a machine appears completely off. Residual charge in capacitors, back-feed from adjacent circuits, and multiple power sources on a single machine are all reasons why de-energising a machine requires more than turning it off.
When Lockout/Tagout Applies to You
Tasks That Require Full LOTO
OSHA 29 CFR 1910.147 requires lockout/tagout whenever an employee performs servicing or maintenance on machinery or equipment and could be exposed to the unexpected energisation, start-up, or release of stored energy. This includes:
- Clearing jams or blockages in machines
- Cleaning, lubricating, or inspecting equipment when guards must be removed
- Adjusting, repairing, or replacing electrical components
- Performing any task that requires placing hands or any part of the body where it could be caught if the machine started
- Working on any equipment with stored hydraulic, pneumatic, or electrical energy
Tasks Exempt From Full LOTO
Minor tool changes and adjustments that are routine, repetitive, and integral to production may be performed without full lockout/tagout, but only if alternative protection is provided, such as a machine guard that prevents contact while the adjustment is made. This exception is narrow and does not apply to any task where a body part could enter the machine’s danger zone.
Cord-and-plug equipment that can be unplugged and the plug kept under the exclusive control of the worker performing the task is also exempt from formal lockout/tagout requirements, but the plug must be physically in the worker’s possession, not simply pulled from the wall and left where someone else could re-insert it.
If you are ever unsure whether a task requires full lockout/tagout, the answer is: lock it out. Applying a lock when it was not strictly required costs two minutes. Not applying a lock when it was required can cost a hand. The threshold for applying LOTO should always err toward more protection, not less.
The Six-Step Lockout/Tagout Procedure
OSHA 29 CFR 1910.147 requires a documented procedure for every machine subject to lockout/tagout. The six steps below are the core of every compliant LOTO procedure.
Before beginning any lockout/tagout, notify all employees who operate or work in the area that the machine will be shut down and locked out. This prevents anyone from starting the machine because they did not know maintenance was in progress.
Identify every energy source feeding the machine: electrical circuits, hydraulic lines, pneumatic connections, gravity-loaded components, and any stored spring energy. Complex machines often have multiple energy sources, and missing even one creates a residual hazard. Your site’s written LOTO procedure for the specific machine must list all energy sources.
Turn the machine off using its normal stopping procedure. This does not de-energise the machine. It is the first step before de-energisation. Do not rely on the normal stop procedure as the only control.
Operate every energy isolating device to disconnect the machine from its energy sources. For electrical equipment, this means opening (turning off) the circuit breaker or disconnecting the disconnect switch. For hydraulic and pneumatic systems, this means closing the valve and bleeding the line.
Apply your personal lock to each energy isolating device. Each worker performing the task applies their own lock. No two workers share a lock. The tag identifies the lock owner and states that the equipment must not be operated. Only the worker who applied the lock removes it.
Attempt to start the machine using its normal start controls. If it does not start, and instruments confirm zero voltage, zero pressure, and no other stored energy, the machine is in a zero energy state and work can begin. If the machine responds or instruments show residual energy, the LOTO was not fully effective and must be corrected before work proceeds.
The verification step is the one most often skipped in practice. Pressing the start button after applying locks is not an empty ritual. It is the only way to confirm that every energy source was correctly identified and isolated. Never skip step 6.
Electrical Lockout/Tagout: What Makes It Different
Multiple Energy Sources and Back-Feed
Electrical equipment often has more than one power source. A machine may receive power from multiple circuits, or may be capable of generating electricity itself (as in the case of motors that can act as generators during coasting). Back-feed from adjacent equipment on the same circuit can energise components that appear isolated.
Your written LOTO procedure for electrical equipment must identify every circuit that can energise the machine and specify the location and operating position of every energy isolating device. If you do not have a written procedure for the specific machine you are working on, stop and get one before proceeding.
Stored Electrical Energy in Capacitors
Large capacitors in industrial equipment can store enough electrical energy to cause fatal electrocution even after the circuit has been opened and locked out. The discharge time for capacitors must be documented in the machine-specific LOTO procedure. Workers must wait for the documented discharge time to pass and verify zero voltage with a calibrated meter before touching any component.
Touching a component that appears de-energised without verifying voltage with a meter is one of the most dangerous assumptions in electrical maintenance. Assume voltage is present until a meter confirms otherwise.
Non-contact voltage testers (the pen-style indicators that beep or light up near live conductors) are useful for initial assessment but are not a substitute for a calibrated multimeter when verifying zero energy state. Non-contact testers can miss voltage in some configurations and do not provide a reading that can be documented. Use a calibrated, category-rated meter and document the zero-voltage verification before beginning electrical work.
Common Lockout/Tagout Mistakes That Cause Injuries
A tagout alone provides no physical barrier. Anyone can remove a tag or ignore it. OSHA requires lockout when the energy isolating device is capable of being locked. Tagout is only permitted when the device cannot physically accept a lock. If your equipment has hasp points for locks and your site has lockout equipment available, use locks.
Your lock goes on. Not your supervisor’s lock. Not a shared lock. Each worker in the danger zone applies their own personal lock. If someone else’s lock is the only lock on the machine, your safety depends entirely on that person not removing their lock while you are working. Personal locks ensure that only you can re-energise the equipment while you are still in harm’s way.
Removing your lock before confirming that all tools are retrieved, all workers are out of the machine, all guards are reinstalled, and all affected employees are notified is a procedural violation that can result in injury to a co-worker. The removal sequence is as important as the application sequence.
The speed of the task is not relevant to whether LOTO is required. A ten-second jam clearance in a machine requires the same lockout/tagout procedure as a four-hour repair. Injuries happen during quick tasks for exactly the same reason they happen during long ones: the energy is still there.
Supervisor and Employer Obligations
Under 29 CFR 1910.147, employers must develop, document, and use energy control procedures for each type of machine or equipment where lockout/tagout is required. The written procedure must specify: the scope of the procedure, the rules and techniques for energy control, and the means to enforce compliance.
Employers must also provide training so that all employees whose work operations are or may be affected by the energy control programme understand the purpose, function, and restrictions of the energy control programme and know how to use it safely.
Periodic inspections of the energy control procedure must be conducted at least annually by an authorised employee other than the one using the procedure being inspected. The inspection must include a review of the procedure with each authorised employee.
If you observe a worker performing maintenance or servicing on a machine without applying lockout/tagout, you must stop the work. Allowing work to proceed without required LOTO makes the supervisor and the employer jointly liable for any resulting injury. A reminder to the worker and documentation of the intervention protect both the worker and the organisation.
LOTO Daily Safety Checklist for Workers
✓ I have a written LOTO procedure for this specific machine before I begin
✓ I have notified all affected employees that the machine will be locked out
✓ I have identified every energy source connected to this machine
✓ I have shut down the machine using its normal stopping procedure
✓ I have isolated every energy source using the energy isolating devices
✓ I have applied my personal lock and tag to each energy isolating device
✓ I have released or restrained any stored energy (bled hydraulics, relieved spring tension, blocked gravity loads)
✓ I have verified zero energy state by attempting to start the machine and confirming zero voltage with a calibrated meter
✓ I will not remove my lock until work is complete, all workers are out, and all guards are reinstalled