Who can remove a lock from a lockout tagout device?

A safety padlock hanging on the circuit breaker, and the key in the hands of one person means that person holds another lifeline. 
This is not literary rhetoric, but the most fundamental safety principle in the LOTO (Lockout/Tagout) procedure. The OSHA (Occupational Safety and Health Administration of the United States) once received a formal inquiry letter from Honeywell Company. The question seemed simple: “Can the master key be used to open the safety lock applied by the employees to the isolation device?” 
The response from OSHA was clear-cut: No. 
This official explanatory letter from 1995 remains to this day one of the most authoritative guidance documents in the field of LOTO regarding “lock removal authority”. It establishes an unshakable principle: each lock can only be removed by the person who applied it, and any “shortcuts” – master keys, backup keys, proxy removal – are breaches of the safety baseline. 
However, in real factories, there are always times when people are absent: employees suddenly fall ill, keys are lost, shift handovers are forgotten… In such cases, how should the lock be opened? Who has the authority to do it? This article will deeply analyze the legal basis, operational norms and common misunderstandings regarding this issue. 
1. Iron Rule: Whoever locks it, shall unlock it
This has been clearly stipulated in OSHA 29 CFR 1910.147(e)(3): 
“Each lockout or tagout device should be removed from each energy isolation device by the employee who applied the device.” 
The seventh step “Release and Restoration” in the Chinese national standard GB/T 33579-2017 “Mechanical Safety – Methods for Hazardous Energy Control – Lockout/Tagout” also requires: 
“Following the principle of ‘who locks, who unlocks’, the locks/tags should be removed one by one by the person themselves.” 
The core logic of this rule can be broken down into three layers: 
Layer1: Personal control
The person who applies the lock (the authorized personnel) is the one who is most aware of whether their work has truly been completed and whether they have completely evacuated the dangerous area. Only he himself possesses all the information necessary to make the judgment of “safety can be restored”. If others are allowed to remove the lock, it is equivalent to entrusting the safety of a worker’s life to another person for judgment – this is something that the LOTO safety philosophy absolutely prohibits. 
Layer 2: Physical Uniqueness
The key to the security lock must be under the exclusive control of the authorized personnel who installed the lock. This means: 
The key can only be held by the employee himself/herself.
It must not be entrusted to others for safekeeping.
The duplicate key must not be duplicated.
The master key system cannot be used as a substitute for removing the lock.
In the explanatory letter, OSHA clearly stated: When the authorized personnel are not present or do not carry the key, using the master key or the duplicate key to remove the lock is not an acceptable removal method. 
Layer 3: Traceable Responsibility
When each lock can only be removed by the person who applied it, the entire removal process has a clear and traceable chain of responsibility: who applied the lock, when it was removed, and whether it was removed under safe conditions – each step has a clearly defined person responsible. This traceability is crucial in accident investigations and compliance audits.