Lockout/tagout (LOTO): isolation, locks and tags

When a technician works inside a machine and someone outside presses the start button by accident, the machine does not ask questions. LOTO rules out that moment: it separates the machine from its energy sources and secures the isolation with a lock and a tag so that nobody can switch it back on by mistake. Let’s look at what LOTO is, how a system is built, and how it connects to the permit to work.

Lockout/tagout (LOTO) isolates equipment from its energy sources during maintenance and secures it with locks and tags. Residual energy is released and the zero-energy state is verified before anyone starts the work. The lock physically prevents; the tag only warns.

Figure 1: the six LOTO steps. The fifth, verifying zero energy, matters most, because a lock proves nothing, only a test or a measurement does.

Who is this for?

maintenance technician · electrician · machine operator · shift supervisor · plant manager · occupational-safety and HSE specialist · contractor.

Learning objectives

• explain the difference between a lock and a tag;
• list the six LOTO steps and justify the order;
• tell a personal lock from a group lockout;
• connect LOTO to the permit to work.

In brief

• LOTO is isolating and securing energy, not just “switching off”.
• A lock physically locks, a tag only signals. Where a lock is possible, use a lock.
• Each worker applies their own lock, and only they remove it.
• Stored energy (pressure, springs, capacitors, gravity) must be released, and zero energy verified.
• LOTO is a condition of the permit: ready before issue, removable after hand-back.

Why does it matter? The stakes

The most common accident pattern is that a stopped machine is restarted by someone who does not know about the work, or that the machine’s stored energy (a compressed spring, a pressurized line) keeps moving after shutdown. LOTO protects the technician against both.

What is the difference between a lock and a tag?

A lockout device is a positive mechanism, such as a lock, that holds an energy-isolating device in a safe position. A tagout device is a warning that does not restrain physically, so it can only be defeated deliberately. Under the US OSHA standard (29 CFR 1910.147), where an energy-isolating device can be locked out, lockout is required unless a tag gives equivalent full protection.

How is a LOTO system built?

The OSHA standard expects an energy control program to include: written, machine-specific procedures (shut-down, isolation, securing, conditions for applying and removing locks), training (authorized, affected and other employees at different levels), a periodic inspection at least once a year by an authorized employee who is not using the procedure under inspection, and a certification of the training. In Hungary the internal LOTO rule and the risk assessment carry the equivalent content; in the sources we reviewed, Hungarian law does not name LOTO as a system, and the duty derives from the general employer’s responsibility (Mvt. § 2 (2), risk assessment § 54). This article uses Hungarian law as an example, not as a universal rule.

Check the current text

The Mvt. and OSHA references were current at the time of writing. Before applying, read the current law and your company’s rule. Educational material, not legal advice.

The six steps in detail

1. Preparation: identify all energy sources (electrical, hydraulic, pneumatic, mechanical, thermal, chemical) and isolation points.
2. Shut down and isolate: stop the machine the usual way, then operate the isolating devices.
3. Lock and tag: each authorized worker applies their own lock and tag, with name and date.
4. Release stored energy: release pressure, relax springs, discharge capacitors, support suspended weight.
5. Verify zero energy: try to start the equipment, or measure; this is the proof.
6. Work, then re-energize: at the end inspect the area, make sure everyone is clear, notify affected staff; the person who applied a lock removes it.

Group lockout

When several people work on the same equipment, personal protection can be provided by a group lockout: one authorized employee carries primary responsibility, the key goes into a lock box, and each worker puts a personal lock on the box when starting and removes it when leaving. The protection level is the same as a personal lock.

How does LOTO relate to the permit to work?

LOTO is the means of isolation; the permit is the decision that work may start after the isolation. As a condition of the permit to work, isolation is ready before issue, holds during the work, and may be removed after hand-back. One important rule: the expiry of a permit does not remove the isolation. If the work continues, the isolation stays and the permit is renewed. The reverse also happens: isolation left in place may go unnoticed at close-out, so close-out needs a specific check.

Implementation in practice: do this tomorrow

Mini-scenario: pick a machine or pipe section and write its LOTO procedure so that a new colleague could carry it out. Ask the maintenance staff: who does not know about this isolation and could still start it? Where anyone says yes, locking and informing is the missing link.

Common mistakes

Mistake	Why it is a problem	Correct practice
A tag without a lock	a tag does not restrain	a lock wherever possible
One shared lock for everyone	nobody knows who is inside	personal locks or a group lock box
Zero energy not verified	stored energy remains	start-up try or measurement
Someone else removes the lock	the person inside does not know	only the applier removes it; exceptions by documented procedure
The permit expires and the isolation is lifted too	work continues unprotected	isolation has a lifecycle independent of the permit

When NOT to use LOTO alone?

Situation	Why it is not enough	What is needed alongside
Process line under pressure	the isolating valve may leak	blind or double block and bleed
Confined space entry	isolation is only one condition	atmosphere test, attendant, rescue
Routine operator intervention	LOTO can be excessive	the simplified protection in your rule
Insufficient competence	a lock does not teach	training, inspection

Take it home

• A lock locks, a tag warns.
• Every worker applies their own lock, and only they remove it.
• Releasing stored energy and verifying zero energy is the point.
• Isolation is a condition of the permit and does not dissolve with it.
• Inspect the procedures annually, by someone who does not use them.

Self-test

1. What is the difference between a lock and a tag, and when is a tag enough?
2. Why does the lock itself not prove zero energy?
3. What should happen to the isolation if the permit expires but the work is not finished?

How does this show up in digital practice?

Principle	Digital implementation	What it prevents
Identified isolation point	points recorded (method, tag, location) and tied to the permit	“something is isolated”
Who and when	applying and restoring with name and time	unknown isolation
Verification	a separate isolation certificate with signature	unverified isolation
Check at close-out	isolation left open is flagged	isolation left in place

Note

The digital system does not replace the lock. It carries on what must be known behind the lock: what, where, who, when.

Connection to OPEREX

In the OPEREX Permit to Work module, isolation points are tied to the permit: method (blind, lock, valve, electrical, drain/vent, other), label, reference, planned, applied and restored states, by who and when, with an audit trail. The separate isolation certificate is a signature in the chain, and the gate before issue looks at the certificate, not at the points. Isolation left open at hand-back or close-out gives a warning, not a block. There is no lock register, group lock box, equipment or CMMS link, and no cross-permit isolation register. Details: isolation and LOTO in the permit, Permit to Work.

Terminology (HU / EN)

Hungarian	English	Note
LOTO, lezárás és megjelölés	Lockout/Tagout	lock and tag
Leválasztás	Isolation	from energy or material source
Lezáró eszköz (lakat)	Lockout device	physical barrier
Címke	Tagout device / tag	warning
Nullenergia-állapot	Zero energy state	verified de-energization
Csoportos lezárás	Group lockout	with a lock box
Jogosult dolgozó	Authorized employee	the person who applies the lock

FAQ

What is a LOTO system?

The system by which, during maintenance, equipment is isolated from all energy sources, the isolating device is locked and tagged, residual energy is released, and the zero-energy state is verified.

Is LOTO mandatory in Hungary?

In the sources we reviewed, Hungarian law does not prescribe LOTO as a named system. The obligation can be derived from the general employer’s responsibility (Mvt. § 2 (2)) and the risk assessment (§ 54); check the current text and your internal rule.

What is the difference between a lock and a tag?

A lock physically prevents re-energizing; a tag only warns. Where the device can be locked, a lock is required.

Who may remove a lock?

As a rule, the person who applied it. Exceptions only under a documented procedure.

How does it relate to the permit to work?

Isolation is a condition of the permit: ready before issue, holding during the work, removable after hand-back. A permit’s expiry does not remove the isolation.

Related concepts

permit to work | confined space | hot work | CMMS | operational risk assessment

Next step

1. Permit to work: the system of which LOTO is a condition.
2. Confined space entry permit: where isolation saves lives.
3. CMMS: the maintenance work the isolation belongs to.

References / further reading

• OSHA 29 CFR 1910.147: The control of hazardous energy (lockout/tagout).
• Mvt.: Hungarian Act XCIII of 1993, § 2 (2), § 54 (njt.hu).
• ISO 45001:2018, clause 8.1.
• HSE (UK): Guidance on permit to work systems (HSG250).