Proving dead is the critical step in the safe isolation procedure where the worker confirms that the circuit or system is genuinely de-energised before touching any conductor or component. This must be done using a voltage indicator that has been tested on a known live source both before and after proving the circuit dead. Relying on the position of a switch or breaker, or assuming isolation is complete because someone else said so, has caused fatal electrocutions on construction sites.
Key Hazards
Electrocution from touching a circuit assumed dead but still energised
Faulty voltage indicator giving a false dead reading on a live circuit
Wrong circuit isolated leaving the intended circuit still live and dangerous
Stored energy in capacitors delivering a lethal shock after the supply is disconnected
Control Measures
Use a voltage indicator compliant with GS38 guidance for all proving dead operations.
Test the voltage indicator on a known live source or proving unit immediately before use.
Prove the circuit dead by testing between all conductors and between each conductor and earth.
Test the voltage indicator again on the known live source immediately after proving dead.
Never rely on the position of a switch, circuit breaker, or isolator as proof that a circuit is dead.
Apply your personal lock and danger tag before proving dead and do not remove them until work is complete.
Check for stored energy in capacitors and discharge safely before touching any internal components.
Prove dead at the point of work, not just at the isolator, to confirm the correct circuit has been isolated.
If the voltage indicator fails any of the prove-test-prove sequence, obtain a replacement before proceeding.
Emergency / Rescue
If you discover a circuit is live when expected to be dead, move away immediately. Do not touch any conductor. Report the failed isolation to the authorised person and investigate which circuit is actually isolated.
Remember
Proving dead using a tested voltage indicator is the only way to confirm a circuit is safe to work on.
The prove-test-prove sequence must be followed every time: test the tester, prove dead, test the tester again.
Never trust the position of a switch or breaker — it may be labelled incorrectly or bypassed.
Prove dead at the point of work because a fault between the isolator and the work location can re-energise.
Capacitors and other energy storage devices can deliver a fatal shock after the main supply is isolated.
A faulty voltage indicator is as dangerous as no indicator at all — test it before and after every use.
Applicable Legislation: Electricity at Work Regulations 1989 · HSG85 (Electricity at Work — Safe Working Practices) · GS38 (Electrical Test Equipment) · Health and Safety at Work etc. Act 1974