Under OSHA 1910.147, use lockout when an energy isolating device can be locked. A tag alone is allowed only if the device cannot be locked, or if the employer shows the tag gives full protection through extra measures. A lock physically prevents operation, while a tag only warns.
The core difference
A lockout device is a positive means, such as a lock, that holds an isolating device in a safe position so it cannot be operated until removed. A tagout device is a prominent warning attached to the isolating device saying it must not be operated.
OSHA's training requirements stress the limit of tags: they are warnings, not physical restraints. They must not be removed or bypassed without authorization, and they must be legible, durable and securely attached.
What the standard says about choosing
If an isolating device cannot be locked out, a tagout system is required. If it can be locked out, lockout is required, unless the employer demonstrates that tagout provides full employee protection.
The standard defines capable of being locked out as having a hasp, an attachment point or a built in lock mechanism, or being lockable without dismantling, rebuilding or permanently altering it.
Making a tag as good as a lock
Full protection under tagout needs the tag in the place the lock would go, a demonstrated safety level equivalent to lockout, and extra measures. The examples listed are removing a circuit element, blocking a switch, opening an extra disconnect, or removing a valve handle.
In practice many sites choose lockout everywhere it is possible, because proving equivalence is work and a tag can be ignored.
Hardware requirements
Lockout devices must resist removal without excessive force or unusual techniques such as bolt cutters. Tagout attachments must be non reusable, attachable by hand, self locking and non releasable, with at least 50 pounds of unlocking strength, comparable to a one piece nylon cable tie. Tags carry a legend such as Do Not Operate. Both must identify who applied them.
Choosing between them: a short decision guide
- Can the isolating device take a lock without being modified? Use lockout.
- If not, can you modify or add a lockable device as part of a planned upgrade? Often the better long term answer.
- If a tag is the only option, document the extra measures, such as removing a handle, and the training on tag limits.
- Re-check at the annual inspection whether a tag only point can now take a lock.
Where control systems complicate this
Where a machine is started from a remote screen or script, the lock on the breaker still works, but only if people remember to treat that command path as an energy source. Add it to your written procedure.
Quick check
Can a tag be used instead of a lock because it is quicker?
No. Convenience is not a basis in the standard. A tag alone is for devices that cannot be locked, or where full protection is demonstrated.
Who must be trained on tag limitations?
The standard requires that tagout training cover tag limitations, and that affected employees be included where tagout is used.
Sources
This is general information, not legal advice.
Last reviewed: 19 October 2026.
