What is the first step in safe isolation procedure?

Lock off the supply at the origin

Test that the equipment is dead

What device should be used to verify isolation?

Approved voltage indicator (AVI)

A non-contact voltage detector pen

A standard digital multimeter on the AC range

What is the proving unit used for?

To prove the voltage indicator is working correctly

To discharge any stored energy in the circuit before work

To indicate the phase rotation of a three-phase supply

To measure the loop impedance at the point of isolation

Free mock exam

Safe Isolation — C&G 2391 Inspection & Testing Practice

Free topic-focused mock exam: 30 random questions from a pool of 35 on Safe Isolation, drawn from the wider C&G 2391 Inspection & Testing bank. 35-minute timer, 70% to pass, worked explanation on every question. Use this when you've taken the full mock once and want to drill the topics you got wrong.

Questions: 30
Time limit: 35 min
Pass mark: 70% · 21/30
Question bank: 35

Free, no sign-up. Retake as many times as you like — different questions each time.

Sample questions

01What is the first step in safe isolation procedure?
- ALock off the supply at the origin
- BTest that the equipment is dead
- CPost the warning notices
- DIdentify the source of supply
Why: The first step is to identify all sources of supply to the circuit or equipment being worked on.
02What device should be used to verify isolation?
- AApproved voltage indicator (AVI)
- BA neon screwdriver tester
- CA non-contact voltage detector pen
- DA standard digital multimeter on the AC range
Why: An approved voltage indicator (AVI) complying with GS38 should be used to verify isolation.
03What is the proving unit used for?
- ATo prove the voltage indicator is working correctly
- BTo measure the loop impedance at the point of isolation
- CTo indicate the phase rotation of a three-phase supply
- DTo discharge any stored energy in the circuit before work
Why: A proving unit is used to prove that the voltage indicator is working correctly before and after testing.

Common questions

Is the Safe Isolation mock exam free?

Yes, it is free with no sign-up needed. Questions are pulled at random from a substantial bank, with a worked explanation on every question after you submit.

Can I retake the mock exam?

Yes. Every attempt picks a different random selection and reshuffles the options, so each retake gives you genuinely new questions. No limit on retakes.

Does this count as a qualification?

No. This is independent practice material and does not award a qualification, card or certificate. Where a subject has a formal qualification or card, you gain it through an approved provider.