Safe Isolation Procedure
Sparks Basics · C&G 2365 Unit 201 · Free course section with an account
Every year electricians are injured working on circuits someone believed were dead. The procedure exists so that belief is never the thing protecting you: you prove your tester works, isolate and secure the supply with your own lock, prove the circuit dead at the point of work, then prove your tester again.
HSE guidance note describes what a suitable indicator and proving unit look like — fused leads, finger barriers, minimal exposed probe tips. Our lessons walk the single-phase three-test check and the full three-phase ten-point sequence until the order is muscle memory.
questions appear in health-and-safety assessments and in practical tests, and interviewers love asking for the sequence out loud. If you can teach it back, you own it.
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Original public revision material · A4:2026. For revision only; do not use samples to guide work on site.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Common questions
- Can I try Safe Isolation Procedure free on this page?
- Yes. The public sample below accepts answers and gives feedback and retries without an account, payment or energy. It is a short revision sample, not the complete course or a full mock paper. This course section is also free with an account.
- Where does Safe Isolation Procedure sit in the City & Guilds scheme?
- Procedure maps to Unit 201. On TradeTraining it lives in the Sparks Basics section as bite-size lessons with practice questions.
- What are the basic steps of safe isolation?
- Identify the circuit, prove your indicator on a proving unit, the supply, secure it with your own lock and warning tag, prove the point of work is dead on all conductor combinations, then re-prove your indicator. If the tester fails the final prove, the dead reading means nothing — start again.
- What is a proving unit for?
- A proving unit is a pocket-sized known source. Testing your voltage indicator against it before and after checking a circuit proves the indicator itself is working — otherwise a broken tester and a live circuit read exactly like a dead one.
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Safe isolation
The procedure that proves a circuit dead before anyone works on it. Prove the voltage indicator against a known source, isolate the circuit, secure the isolation with your own lock and tag, prove the point of work dead across all conductor combinations, then prove the indicator again. The final step is the one that catches a tester that died mid-job.
Read the full Safe isolation glossary entryGS38
The HSE's guidance note on electrical test equipment used by electricians. It describes what safe voltage indicators, probes and leads look like: fused or current-limited leads, finger barriers, minimal exposed probe metal, and a proving unit to verify the indicator before and after use. 'GS38-compliant' is shorthand for test kit you can trust your life to.
Read the full GS38 glossary entryPolarity
Verification that conductors are connected the right way round throughout an installation. Single-pole switches and protective devices must sit in the line conductor, the centre contact of screw lampholders on line, and socket terminals wired as marked. A polarity fault can leave equipment live when switched off — which is why it is checked dead and confirmed again live.
Read the full Polarity glossary entryBasic protection
Protection against touching live parts during normal, fault-free service. It is delivered by insulation around conductors, barriers and enclosures around terminals, and placing live parts out of reach. It is the first layer of shock protection; fault protection is the second, and an installation needs both.
Read the full Basic protection glossary entry