Safe Isolation and Risk Assessment
Risk assessment on site
Risk assessment is a continuous process, not a document written once. The five-step model - identify the hazards, decide who might be harmed and how, evaluate the risks and decide on precautions, record and implement, review and update - underpins the dynamic risk assessment you make every time conditions change: another trade arrives, a floor is opened up, or a board turns out to contain more supplies than the drawing showed.
Apply the hierarchy of control: eliminate, substitute, engineering controls, administrative controls, and PPE as the last resort. On electrical work the engineering control is usually the isolation itself. Prepare a method statement and, where the work is complex or high energy, a permit to work. Hazards on an AM2-style installation include unexpected supplies (PV, generators, UPS, dual-tariff boards), asbestos in older buildings, buried services, work at height, and other people's live equipment inside shared enclosures.
For the isolation, use GS38-compliant equipment: fused test leads, finger guards, and no more than about 4 mm of exposed probe tip. Lock off with a padlock and warning notice and keep the key personally - a tag alone is not isolation.
The classic trap is assuming one device isolates everything. A borrowed neutral, a shared supply or a second consumer unit can leave conductors live. Test between every pair - line–neutral, line–earth, neutral–earth, and line–line on three-phase - at the point of work, not back at the board.
Rule of thumb: prove–test–prove. Prove the tester on a proving unit, test the conductors, then prove the tester again. If it cannot be proved after the test, the result is void.