In our regular column, the experts from NEBOSH answer your safety questions. On this month’s agenda, is increasing awareness of lockout tagout.

“I’ve heard of lockout-tagout, but I’m not sure exactly what’s involved or when the process would be used. Is it something that should be incorporated into my organisation’s health and safety training?

Lockout-tagout (LOTO) is a safety procedure that stops potentially dangerous machinery being operated during activities such as repair, maintenance and cleaning. It’s widely used in hazardous operations across a range of industries.

LOTO is a simple way to protect workers but it needs to be used properly. It is worth noting that an inconsistent LOTO procedure (as part of a permit system) was one of the failings identified in the Piper Alpha offshore oil platform disaster of 1988 (which cost the lives of 167 workers).

As with any safety procedure, everyone involved in LOTO needs to be competent to carry out their individual responsibilities, which includes being adequately trained. Training should be given to everyone involved in the operation, maintenance and repair of the machine, including operators, supervisors, maintenance workers, contractors and subcontractors.

What does LOTO involve?

LOTO is a system for isolating (and de-energising) a machine from its potentially hazardous energy sources. This is to prevent accidental or inappropriate activation of the machine, which could injure anyone working on or near it. Depending on the machinery, LOTO might involve the isolation of corrosive chemicals (including locking and tagging equipment isolating valves), electricity, hydraulic pressure, pneumatic pressure, gases or moving parts. Everyone involved in the maintenance, repair and operation of the machine – and anyone working in the vicinity – needs to be aware of LOTO procedures.

When is it used?

LOTO is generally used in situations that fall outside standard operating procedures; for example, when the machine needs repair or maintenance, or where a risk assessment indicates a higher level of risk due to a particular activity.

Lockout is designed to protect both the operator and individuals who wouldn’t normally be there, such as maintenance technicians or contractors there for shutdown. If carried out correctly, LOTO should ensure that nobody is exposed to danger.

How does LOTO work in practice?

To lock out a machine, the nominated person responsible for the machine (which could be the operator or supervisor) places a multi-lock hasp on the source of hazardous energy and attaches their padlock and a tag (and a brief description of what the tag is for e.g. corresponding information about the task) to it. Anyone else working on the machine then attaches their own individual padlock (e.g. with the department and individual’s name / colour coded department and individual’s name etc.) to the hasp.

Before the machine can be re-energised, each person must remove their padlock in reverse sequence (the “cascade locking system”), until the only padlock remaining is the one belonging to the nominated person (who can be the operator in charge of preparing the machine for start-up). When the operator is satisfied the work is complete and the machine is safe to use, they remove their lock and the hasp.

The hasp ensures the machine cannot be switched on until all of the padlocks and the tag have been removed and the operator is happy to restart normal operation.

Why is training so important?

It is vital that employers train all relevant staff and contractors on LOTO procedures so they are clear about when lockout must be used; who is responsible for lockout (is it the machine’s operator or a supervisor?); who they can report concerns to; and what to do in the event of a deviation from procedure.

LOTO could be regarded as almost foolproof: when performed correctly, it should safeguard workers from hazardous energy sources. But it relies on individuals understanding their roles and carrying them out properly.

Anyone (internal or contractor) that could potentially be involved in a lockout situation should have LOTO procedures covered in their inductions.

Lapses in procedure may not only cause operational delays, but can increase the risk of someone being harmed. For example, if a contractor fails to remove their personal padlock after completing their work and then goes off site, the operator responsible for the machine will have to decide whether it is safe to restart the machine. They will need to assess the risks and seek high-level authorisation before they can even consider removing the lock forcibly (a last resort) and recommissioning the machine. Operatives will need training on what to do in these circumstances, so they know how to proceed safely.

NEBOSH offers two qualifications that cover LOTO: the NEBOSH HSE Certificate in Process Safety Management, and the International Technical Certificate in Oil and Gas Operational Safety. Visit to find out more.

Don’t forget to review

If LOTO procedures are working well, their use across site should become the cultural norm. And LOTO is a sound, efficient system: when used correctly, problems are unlikely to occur. But employers must ensure there is a process for reporting issues, and that they regularly audit to see how well LOTO procedures are working in practice. They should also invite and welcome feedback on workability, because a poor system is more likely to be abused or bypassed.