In 2021, a maintenance technician at an automotive parts factory in Michigan, USA, discovered that his safety lock key was missing during shift change. The lock was still attached to the circuit breaker, and the equipment was in a locked state, with the next shift’s production line waiting to resume operation. He hesitated for ten minutes before finally using a screwdriver to pry open the lock – the lock was damaged, but the worse part was that when the equipment was restored to power, a worker who was cleaning cutting waste inside the machine almost got caught in the conveyor belt.
This attempted accident revealed a seriously underestimated risk point in the LOTO (Lockout/Tagout) system: What to do when the lock cannot be found or the key is lost? This is not a rare event. According to statistics from the National Safety Council (NSC), in industrial enterprises that implement the LOTO procedure, approximately 12% of annual LOTO-related violations are directly related to “inadequate lock or key management”. In China, as more manufacturing enterprises introduce the LOTO system, this issue has become increasingly prominent.
1. First, clarify: Is it “the key is lost” or “the lock is missing”?
Before formulating a response plan, it is necessary to clearly distinguish between the two different situations, as their urgency and handling paths are completely different.
1.1 Key loss
This is the most common situation. The lock is still attached to the isolation device, the equipment is in a locked state, but the authorized personnel cannot find the key to unlock it. At this time, the equipment cannot be restored to operation, production is affected, but the safety status itself has not been compromised – the equipment is still locked and there is no risk of accidental startup.
Core contradiction: Conflict between production efficiency and safety procedures. The greater the time pressure, the greater the temptation to violate the procedures.
1.2 Lock disappearance
This is much more serious than key loss. The lock has disappeared from the isolation device. The reasons could be:
The lock was removed or cut by unauthorized personnel
The lock fell off during operation (installation was improper)
The lock was stolen or maliciously damaged
The lock was mistakenly regarded as an abandoned lock and was cleared
Core danger: The equipment may have been out of the lockout protection, and anyone could mistakenly think the equipment is still in a safe state and enter the dangerous area. This is an immediate stop-all-operation and start emergency procedures level.
2. Emergency response for key loss
When the authorized personnel confirm that the key is lost, they must follow the following procedures strictly. Any skipping of steps can lead to serious consequences.
Step 1: Immediately stop the operation and report
At the moment the key is lost, the authorized personnel must do two things:
Stop all operations related to this isolation point – not “look for it first” but stop immediately
Report to the immediate supervisor – oral report + written record
The report content should include:
The time of loss (as precisely as possible)
The location and time of the last confirmation of the key in hand
The identification information of the key (lock number, key number)
The current status of the equipment and isolation point
The list of people present
Key reminder: Do not spend half an hour “looking for the key” before reporting. Many accidents occur during this “looking for the key” period – because the operator is distracted looking for the key and neglects the safety of the operation. After reporting, the supervisor can organize personnel to assist in the search and simultaneously start the formal emergency procedure.
Step 2: Confirm that the key is indeed lost
Before starting the formal removal procedure, a systematic search is required to ensure that the key is not left in a pocket, toolbox, or operation area.
Search list:
Personal protective equipment pockets (work clothes, vests, coats all pockets)
Toolboxes and tool carts (thoroughly check each layer)
The ground of the recent operation area (kneel to check the bottom of equipment, corners)
Cabinets and personal storage lockers
Recent passageways and corridors
Near the equipment control panel (whether it was placed on the panel by accident) Reception area / restroom (whether the keys were taken out and forgotten during rest)
Vehicle (if driving to the work site)
Search principle: At least two people should participate in the search, and the search time should not exceed 30 minutes. If not found within 30 minutes, proceed to the next step.
Step 3: Activate the emergency removal procedure
After confirming that the keys are lost, the lock should be removed according to the emergency override procedure. The core of this step is: You cannot remove the lock just because you want to; it must be done in accordance with the written procedure and by authorized personnel.
According to OSHA 1910.147(e)(3), when the authorized personnel responsible for the lock cannot remove it themselves, the employer can guide the removal, but the following three conditions must be met:
A written procedure has been established – the enterprise’s energy control procedure must already include emergency removal provisions
Equivalent safety assurance – the removal process must provide equivalent safety assurance to a personal removal
Specific training has been completed – the personnel performing the removal must have received relevant training
GB/T 33579-2017 “Mechanical Safety – Methods for Hazard Energy Control – Locking and Tagging” also requires: When the authorized personnel are not present, the lock removal should be carried out according to the pre-established written procedure, and the removal process must ensure that it does not endanger the safety of any personnel.
Step 4: Independent zero-energy verification
Before removing the lock, an independent qualified person from outside the original operation team must verify the zero-energy state of the equipment. This is the most critical safety step – because you don’t know whether the operation was truly completed before the keys were lost by the original operation personnel.
Core principle: The verification personnel must sign an independent zero-energy verification report. This report is a prerequisite for removing the lock – without this signed report, no one can remove the lock.
Step 5: Physical removal of the lock
After confirming the zero-energy state, the lock can be physically removed. There has been a long-standing debate in the industry about this issue: Should you cut the lock with a wire cutter or open it with a spare key/total key?
Wire cutter cutting method (industry recommendation)
Advantages:
The lock is physically damaged and cannot be reused, eliminating the risk of “the lock being reattached but the key not in the authorized person’s possession”
No need to manage spare keys or total keys, eliminating the risk of key management
The process has a visual impact, and all on-site personnel can clearly see “the lock has been forcibly removed”
Complies with the spirit of OSHA’s 1995 explanatory letter to Honeywell
Key points of operation:
Operated by designated authorized personnel
Supervision by the supervisor and safety representative on site
Video or photos of the removal process should be archived
The remaining lock fragments are retained, labeled with the removal date, reason, and authorized person
Spare key/total key method (conditionally accepted)
OSHA issued an amended explanatory letter in 2000, stating that spare keys/total keys can be used under extremely strict conditions, but the threshold is extremely high:
Spare keys must be stored in a secure lock cabinet, double-lock management by two people
Each use must be subject to written approval
The use record is complete and traceable
Spare keys are only used for emergency removal and not for daily operations
Industry consensus: Even if conditions permit, the wire cutter cutting method is preferred. Because if the spare keys/total key system is poorly managed, it will turn into a situation where “anyone can open the lock”, completely undermining the foundation of the LOTO system. Notify relevant personnel that the equipment has been restored to use.
Step 6: Restore energy and verify operation
After the lock is removed, follow the normal LOTO recovery procedure:
Confirm that the work area has been cleared (tools, materials, waste)
Confirm that all personnel have evacuated the hazardous area
Confirm that the safety protection devices have been reset
Notify all affected personnel that the equipment is about to resume operation
Restore energy supply in the correct sequence
Verify that the equipment is operating normally Notify relevant personnel that the equipment has been restored to use.
Post time: Aug-06-2026
