What does the Electricity at Work Regulations 1989 say about isolation?

Regulation 12 of the Electricity at Work Regulations 1989 requires that where necessary to prevent danger, suitable means shall be available to cut off the supply of electrical energy to any electrical equipment. Regulation 13 requires that adequate precautions be taken to prevent electrical equipment, which has been made dead in order to prevent danger while work is carried out on or near that equipment, from becoming electrically charged during that work. These regulations apply to all workplaces in Great Britain and impose duties on both employers and employees.

What is the correct safe isolation procedure for a domestic consumer unit?

The approved sequence is: (1) Identify the correct circuit breaker or fuse for the circuit to be worked on. (2) Switch off the breaker or remove the fuse. (3) Apply a MCB lockout clip and your personal padlock, or place the fuse in your pocket. (4) Prove your approved voltage indicator (AVI) on a known live source. (5) Test the circuit at the point of work — between L-E, L-N, and N-E. (6) Prove the AVI again on the known live source. All six tests must read zero volts or the installation is not dead. Only then is it safe to begin work.

What voltage indicator should I use for safe isolation?

You must use an approved voltage indicator (AVI) that complies with GS38 — the Health and Safety Executive guidance note on test equipment for electricians. A compliant AVI will have: fused test leads with shrouded probes, finger barriers or adequately shrouded tips, leads rated for the voltage being tested, and a clear indication of live/dead status. Common compliant AVIs include the Fluke 1AC-A1-II, Martindale VP1, and Kewtech KT100. A multimeter alone is not an approved voltage indicator for safe isolation purposes in the UK.

What is the difference between lockout and tagout?

Lockout involves physically locking an isolation device in the off position with a padlock so that the circuit cannot be re-energised without the key. Tagout involves attaching a warning tag to the isolation device, but without a physical lock. UK electrical safety guidance strongly prefers lockout over tagout wherever the isolation point accepts a lock. Tagout alone is only acceptable where the isolation point cannot physically be locked — and even then, additional precautions must be taken. The HSE and UK industry best practice require personal padlocks so that each worker controls their own safety.

When is a permit to work required?

A permit to work (PTW) is required whenever the consequences of an error in isolation could be catastrophic — for example, on high-voltage systems, in confined spaces with electrical equipment, on process plant where re-energisation could cause injury to multiple people, or on any system where more than one trade is working simultaneously. Many industrial and commercial clients specify PTW systems for all electrical work regardless of voltage. The permit defines the scope of work, confirms that isolation is complete, specifies safety precautions, and must be signed off by an authorised person before work begins and when it is complete.

What happens when multiple trades are working on the same isolated system?

Each person working on an isolated circuit must apply their own personal padlock to the isolation device using a multi-lock hasp. This hasp (also called a hasp-and-staple device) accepts multiple padlocks so that the circuit cannot be re-energised until every worker has removed their padlock. The last padlock is removed by the authorising person when work is complete and all workers have confirmed they are clear. This system ensures that no single person can inadvertently restore power while others are still working.

Can I work live if isolation is not possible?

Live working is only permitted in exceptional circumstances under the Electricity at Work Regulations 1989 (Regulation 14). To work live, it must be unreasonable in all the circumstances for the conductor to be dead, and suitable precautions must be taken to prevent injury. Live working requires specific employer authorisation, risk assessment, use of insulated tools complying with IEC 60900, appropriate PPE (insulated gloves, face shield), a second competent person present, and a rescue plan. Live working is not a routine alternative to safe isolation — it should be the last resort.

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Lockout Tagout (LOTO) Guide UK: Safe Electrical Isolation

The complete UK guide to lockout tagout and safe isolation procedures. Covers the Electricity at Work Regulations 1989, the prove-dead sequence, LOTO device types, permit to work systems, and multi-trade isolation — everything qualified electricians need to work safely.

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12 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

1The Electricity at Work Regulations 1989 (Regulation 12) require that every electrical circuit be capable of being made dead before work begins. Failure to isolate before working on electrical systems is one of the most common causes of fatal accidents in the UK electrical industry.
2Safe isolation follows a defined sequence: identify the correct isolation point, isolate, apply lockout/tagout devices, prove dead with a calibrated voltage indicator, prove the voltage indicator works on a known live source, then confirm dead — this is the "test before touch" principle.
3A voltage indicator alone is not sufficient proof. The approved voltage indicator must be proved on a known live source before and after testing. Many electricians use a proving unit (such as the Fluke PRV240 or Kewtech KT230) to prove the indicator.
4Lockout tagout (LOTO) devices include padlocks, hasp-and-staple devices, MCB lockouts, plug lockouts, fuse lockout boxes, and lockout stations. Each person working on an isolated circuit must apply their own personal padlock.
5Permit to work (PTW) systems provide a formal, documented authorisation for high-risk electrical work. They are mandatory on many industrial sites and are required under the Electricity at Work Regulations 1989 for work near live systems.

01 · Safety Guide

Legal Basis — Electricity at Work Regulations 1989

The Electricity at Work Regulations 1989 are the primary legislation governing safe isolation in the UK. They impose absolute duties on both employers and employees — there are no qualifications such as "so far as is reasonably practicable" in many of the key regulations.

Regulation 12 — Means for cutting off the supply and for isolation — where necessary to prevent danger, suitable means shall be available to cut off the supply of electrical energy to any electrical equipment. Every isolation point must be identified and capable of being made dead.
Regulation 13 — Precautions for work on equipment made dead — adequate precautions must be taken to prevent electrical equipment that has been made dead from becoming electrically charged during the work. This is the legal foundation for lockout tagout procedures.
Regulation 14 — Work on or near live conductors — no person shall work on or near a live conductor (other than one suitably insulated) unless it is unreasonable in all the circumstances for it to be dead, suitable precautions are taken, and it is reasonable in all the circumstances to work on or near it live.
Breach is a criminal offence — failure to comply with the Electricity at Work Regulations 1989 is a criminal offence under the Health and Safety at Work etc. Act 1974. Convictions can result in unlimited fines and imprisonment for up to two years.

The HSE publication HSG85 (Electricity at Work — Safe Working Practices) provides detailed guidance on implementing the regulations. It is freely available from the HSE website and should be on every electrical contractor's bookshelf.

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02 · Safety Guide

Safe Isolation Procedure — Step by Step

Safe isolation is a defined sequence of steps that must be followed every time before working on an electrical circuit. Skipping any step — even once — can be fatal.

1Identify the circuit — confirm which circuit serves the equipment to be worked on. Check the distribution board schedule. Test with an approved voltage indicator at the point of work to confirm which circuit is which before isolating. Never assume the schedule is accurate.
2Isolate — switch off the MCB, withdraw the fuse, or operate the isolator. Confirm the device is in the off or open position visually.
3Secure the isolation point — apply your MCB lockout clip and personal padlock, or place the fuse in your personal possession. Attach a warning tag stating your name, the date, and the work being carried out.
4Prove the voltage indicator on a known live source — before testing the isolated circuit, confirm your approved voltage indicator (AVI) is working correctly by testing it on a known live supply or proving unit.
5Test the circuit — prove dead — at the point of work, test between all conductors: L-E, L-N, and N-E. All must read zero volts. On three-phase systems, test all combinations: L1-L2, L2-L3, L3-L1, L1-E, L2-E, L3-E, N-E.
6Prove the voltage indicator again on the known live source — confirm the AVI is still working after testing the isolated circuit. Only when this final check passes can you be confident the circuit is dead.

This six-step sequence is sometimes called the "prove-test-prove" method. It is the approved UK method for safe isolation and is endorsed by the HSE, NICEIC, and industry training bodies.

03 · Safety Guide

Proving Dead — Test Before Touch

"Test before touch" is the fundamental principle of electrical safe isolation. It means you must prove that a circuit is dead before touching any conductors — even if you isolated it yourself. Never assume a circuit is dead; always test.

GS38 compliant voltage indicator — the HSE guidance note GS38 specifies the requirements for electrical test equipment used by electricians. Your approved voltage indicator (AVI) must have adequately rated and fused test leads, finger barriers or shrouded probes, and a clear live/dead indication.
Use a proving unit — a proving unit (such as the Fluke PRV240, Kewtech KT230, or Martindale PD690) generates a known safe voltage that can be used to prove your AVI is functioning correctly both before and after testing the isolated circuit. This eliminates the risk of using a faulty indicator.
Single-pole indicators are not sufficient — testing only line to earth is not adequate. You must test all combinations of conductors at the point of work. Some circuits have capacitive stored charge or parallel feeds that can re-energise a circuit after isolation.
Discharge capacitors — capacitors in motor starters, VSD drives, and power factor correction equipment can retain a dangerous charge for several minutes after isolation. Follow manufacturer discharge procedures before working on this equipment.

The proven dead state only applies at the time of testing and at the point of work. If you move to a different part of the circuit, or if time passes, you must test again before touching conductors.

04 · Safety Guide

LOTO Device Types — Padlocks, Hasps, and Lockout Stations

Lockout tagout devices physically prevent an isolation point from being re-energised while work is in progress. Selecting the correct device for each type of isolation point is essential.

Personal padlocks — each worker must have their own padlock with a unique key. Safety padlocks are typically brightly coloured and have a non- conductive shackle. Each person retains their key for the duration of the work. Common brands include Master Lock, ABUS, and Brady.
Multi-lock hasps (hasp-and-staple devices) — a hasp accepts multiple padlocks simultaneously. It is applied to the isolation point and each worker applies their own padlock. The circuit cannot be re-energised until all padlocks are removed. Essential for multi-trade working.
MCB lockout clips — snap-on devices that fit over a miniature circuit breaker in the off position and accept a padlock shackle. Available for most common MCB profiles including DIN-rail types. A padlock must also be applied — the clip alone is not lockout.
Plug lockouts — lockout devices that encase a plug so that it cannot be inserted into a socket. Used when the isolation point is a plug and socket rather than a fixed device. Available for 13A, industrial (BS EN 60309), and CEE plug types.
Fuse lockout boxes — a box that retains a withdrawn fuse and accepts a padlock. Prevents the fuse from being re-inserted until the box is unlocked. Used where fuse withdrawal is the method of isolation.
Lockout stations — shadow boards or cabinets mounted near high- risk equipment containing all required LOTO devices, padlocks, tags, and permit documentation. Required on industrial sites where multiple isolation points are managed simultaneously.

Warning tags (danger tags) must accompany lockout devices. They should state the reason for isolation, the name of the person who applied the lock, and the date. Tags alone without a physical lock do not constitute lockout.

05 · Safety Guide

Permit to Work Systems

A permit to work (PTW) is a formal documented system for controlling high-risk electrical work. It provides a written authorisation from a responsible person that the equipment has been isolated, tested dead, and is safe to work on.

When PTW is required — high-voltage systems (above 1,000V AC), work in confined spaces with electrical equipment, complex industrial plant, any situation where multiple trades share the same isolation, and wherever the client's safety management system requires it.
Authorised person (AP) — the AP is responsible for issuing the PTW. They must be competent to understand the electrical hazards and confirm that isolation is complete. The AP countersigns the permit when work is complete and authorises re-energisation.
Permit contents — scope of work, equipment identification, isolation method and points, tests carried out and results, additional precautions (earthing, barriers, PPE), names of all workers covered by the permit, duration of validity, and sign-off procedures.
Cancellation and reinstatement — a PTW must be formally cancelled before equipment is re-energised. If work is interrupted (end of shift, emergency), the permit must be suspended and a new permit issued when work resumes. Equipment must be re-tested before work recommences even under a reinstated permit.

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06 · Safety Guide

Multi-Trade Isolation

When multiple trades or individuals work on the same isolated system simultaneously, each person must independently control their own safety. The multi-lock hasp system is the approved UK method for managing this.

Each worker applies their own padlock — after the authorising person has confirmed isolation and applied the first lock, each additional worker applies their own personal padlock to the hasp. No single person can remove all locks — including the authorising person.
Shift handover — when shifts change, the outgoing worker removes their padlock and the incoming worker applies theirs. There must be no period when the isolation point has no lock applied during the handover.
Lost key procedure — if a worker loses their padlock key, a documented emergency procedure must be followed. This typically involves confirming the worker is clear of the circuit, cutting the lock under supervision of the authorising person, and recording the incident. Never remove someone else's padlock without following this procedure.
Contractors on site — visiting contractors must apply their own padlocks to any LOTO device before starting work. Do not rely on the host site's isolation alone. The host should issue a PTW confirming isolation, and the contractor applies their personal lock as additional protection.

07 · Safety Guide

Identifying Isolation Points

Before any electrical work begins, the correct isolation point must be positively identified. Isolating the wrong circuit is as dangerous as not isolating at all.

Check the distribution board schedule — confirm the circuit description matches the equipment to be worked on. Board schedules are often inaccurate, particularly in older or modified installations.
Test at the point of work before isolating — use your AVI to confirm the circuit is live at the point of work, then switch off the suspected MCB and confirm the circuit goes dead at the point of work. This positively identifies the correct isolation device.
Parallel feeds and sub-distribution — in complex installations, a piece of equipment may be fed from more than one source. Check for sub-boards, local isolators, and UPS systems. Test the equipment terminals for voltage after isolating at the main board before assuming it is dead.
Buried and concealed cables — when chasing walls or cutting into floors, use a cable detection device before starting. Cables do not always follow expected routes, particularly in older buildings. Consult the full electrical safety guide for detection device guidance.

08 · Safety Guide

For Electricians: RAMS and Safe Isolation Documentation

Documenting safe isolation procedures in your RAMS (Risk Assessment and Method Statement) protects you legally and demonstrates to clients that you operate to the highest professional standards. It is also a requirement under the Construction (Design and Management) Regulations 2015 for notifiable projects.

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Frequently Asked Questions About Lockout Tagout and Safe Isolation

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Lockout Tagout (LOTO) Guide UK: Safe Electrical Isolation

Key Takeaways

Legal Basis — Electricity at Work Regulations 1989

Get the BS 7671 A4:2026 Cheat Sheet — free

Safe Isolation Procedure — Step by Step

Proving Dead — Test Before Touch

LOTO Device Types — Padlocks, Hasps, and Lockout Stations

Permit to Work Systems

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Multi-Trade Isolation

Identifying Isolation Points

For Electricians: RAMS and Safe Isolation Documentation

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Frequently Asked Questions About Lockout Tagout and Safe Isolation

What does the Electricity at Work Regulations 1989 say about isolation?

What is the correct safe isolation procedure for a domestic consumer unit?

What voltage indicator should I use for safe isolation?

What is the difference between lockout and tagout?

When is a permit to work required?

What happens when multiple trades are working on the same isolated system?

Can I work live if isolation is not possible?

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