Work in Compressed Air Regulations 1996 — Tunnelling, Caisson Work and Cleaning in Pressurised Environments

The Work in Compressed Air Regulations 1996 apply to work carried out in a compressed air environment -- typically tunnelling operations using pressurised tunnel boring machines, caisson sinking, and foundation work in compressed air where groundwater pressure is counteracted by air pressure. These are highly specialised construction operations. The Regulations set requirements for medical fitness, decompression procedures, compressed air contractor competency, on-site medical facilities and emergency procedures. Cleaning and maintenance activities within pressurised tunnels and caissons are subject to the same regulatory framework as the primary compressed air work.

The cleaning equipment implications

Equipment used in compressed air environments must be suitable for pressurised operation. Standard industrial pressure washers and vacuum cleaners are designed for atmospheric pressure operation. In a compressed air environment:

Electrical equipment must be suitable for the atmospheric conditions -- increased oxygen partial pressure affects fire and explosion risk
Compressed air within the tunnel can be used as a power source for pneumatic cleaning equipment -- pneumatically powered vacuums and pressure washing equipment eliminates the electrical safety concern
Dust generated by cleaning in a compressed air environment is subject to the same COSHH requirements as surface dust -- M-Class or H-Class extraction as appropriate for the dust type
Compressed air at higher than atmospheric pressure affects the behaviour of pressure washing equipment -- higher ambient pressure means lower differential pressure from the pump

For specialist tunnelling contractors, cleaning equipment specification for compressed air working should be confirmed with the compressed air contractor and the project health and safety advisor before procurement.