Risk assessment, permits to work and safe systems of work
Risk assessment, permits to work and safe systems of work
This domain tests how you build a defensible safe system around a confined space or hot work task, and where gas testing fits.
Core rules
- Avoid entry first. Use remote cameras, sampling lines or external work wherever reasonably practicable. The Confined Spaces Regulations put avoidance above all other controls.
- Risk assessment must consider the atmosphere (oxygen, flammable, toxic), residues and sludge, isolation, engulfment, access and egress, adjacent operations, temperature, noise and the rescue plan. It must be site-specific and revised when conditions change.
- Isolation includes lock-out/tag-out, blinds or spades, double block and bleed, and disconnection of services. Purging and ventilation follow isolation.
- Permit to work (PTW) is the formal record that controls the task. It should state the location, task, hazards, controls, gas test results, validity period, signatures and handover/cancellation arrangements. The gas certificate is often attached but is not the whole permit.
- Safe system of work links the permit, testing, ventilation, communications, standby arrangements, PPE and rescue plan.
- Simultaneous operations (SimOps) matter: vehicle exhaust, welding fumes, solvent use or adjacent purging can change the atmosphere after your last test.
Worked example
A diesel storage tank is to be entered for inspection. Reasoning: diesel has a flashpoint above ambient but sludge can release flammable vapour; the vapour is heavier than air and collects at the bottom. The risk assessment must require draining and cleaning, isolation of all lines, purging and ventilation, testing at top, middle and bottom, a permit with a defined re-test interval, a standby person and a rescue plan with retrieval equipment.
Traps
Using the permit as the risk assessment; one test for the whole job; forgetting rescue and communication; failing to re-test after a break, shift change or adjacent activity; allowing ventilation to be switched off once the permit is signed.