Compressed Air Regs 1996: HSE Work in Compressed Air Rules

Regulatory citation: Work in Compressed Air Regulations 1996 (SI 1996/1656)

What Are the Work in Compressed Air Regulations?

The Work in Compressed Air Regulations 1996 control construction work carried out in air pressurised above normal atmospheric pressure. This is mainly tunnelling, where compressed air is used to keep ground water out of the works. The Regulations apply to work in a working chamber, airlock or decompression chamber where the pressure exceeds 0.15 bar, including medical locks used for treatment. They do not apply to diving.

Why Compressed Air Work Matters

Working under pressure and decompressing incorrectly can cause decompression illness. Fire is a particular hazard, and getting people out of a pressurised chamber in an emergency takes time. The Regulations set out how the work must be planned, supervised and medically supported.

Core Requirements

1. Appoint a Compressed Air Contractor (Regulation 5)

The principal contractor must appoint a competent contractor to carry out or supervise the compressed air work, or may take on the role itself if competent. HSE notes that the compressed air contractor is usually, but not always, the principal contractor under CDM 2015.

2. Notify HSE and Emergency Services (Regulation 6)

Written notice must reach HSE at least 14 days before the work starts, or as soon as practicable in an emergency. Notice must also go to relevant hospitals with accident and emergency units, local ambulance and fire services and nearby establishments with a working medical lock. Schedule 1 lists what to include, such as the site, dates, maximum intended pressure, shift pattern and the contract medical adviser's details.

3. Use a Safe System of Work (Regulations 7–8)

No one may work in, enter or leave compressed air except under a safe system of work. Enough competent people must supervise on site while work is going on, and for 24 hours afterwards where the work was at 0.7 bar or more. Plant must be suitable and maintained, and equipment holding air above 0.15 bar must be examined and tested by a competent person before work starts and after modifications.

4. Provide Medical Surveillance (Regulations 9–10)

The contractor must appoint a contract medical adviser. Workers need surveillance by an appointed doctor before they first work in compressed air, then at intervals of not more than 12 months. Health records must be kept for at least 40 years from the last entry.

5. Follow Approved Decompression Procedures (Regulation 11)

Compression and decompression must follow procedures approved by HSE. No one may be subjected to pressure above 3.5 bar except in an emergency, and decanting is allowed only in an emergency. Exposure records, including time of entry, duration, maximum pressure and decompression details, must be kept for 40 years. HSE notes that oxygen breathing during decompression has been required since 2001.

6. Provide Treatment and Emergency Arrangements (Regulations 12–13)

Treatment facilities must cover current workers and anyone who has worked in compressed air in the previous 24 hours. At 0.7 bar or more this includes a medical lock and people competent to run it and give medical help. At 1.0 bar or more, a dedicated person competent to do both must be available. Suitable emergency, alarm and access arrangements are required.

7. Control Fire, Fitness and Welfare (Regulations 14–19)

Smoking and smoking materials are banned in compressed air, as is alcohol. No one may work if believed to be unfit or impaired. Workers need information and training, drinks after decompression and facilities to stay on site. At 0.7 bar or more each worker must get a badge or label to wear for 24 hours after leaving compressed air, so others know what to do if they become ill.

Common Compliance Approaches

Plan Notification Early

Build the 14-day notice and contact with hospitals and fire services into the project programme before mobilising plant.

Use Current Industry Guidance

HSE has withdrawn its L96 guide but states the Regulations remain unchanged. It points dutyholders to British Tunnelling Society guidance.

Track Every Exposure

Keep lock logs and individual exposure records from day one, and give workers copies when they leave the project.

Example: Compressed Air Work in Practice

A tunnelling contractor plans a short drive under a river at 1.2 bar. It notifies HSE, the local hospital and fire service three weeks ahead, appoints a contract medical adviser and arranges pre-entry medicals for the crew. A medical lock is set up at the shaft with a trained lock attendant who can also give medical help. Lock keepers follow the approved decompression procedure with oxygen breathing, log every shift and issue badges that workers wear for 24 hours after each shift.

Related regulations: CDM 2015 construction duties, Diving at Work Regulations 1997, PSSR 2000 pressure systems.

Note: This summary reflects the Regulations as they apply in Great Britain, enforced by HSE. legislation.gov.uk holds only the original text, which refers to construction regulations that have since been replaced; HSE states that CDM 2015 applies to compressed air projects. Northern Ireland has equivalent but separate legislation. Always check the current legislation and HSE guidance.

Frequently Asked Questions

At what pressure do the Compressed Air Regulations apply?

They apply to construction work in a working chamber, airlock or decompression chamber where the pressure is more than 0.15 bar above atmospheric pressure.

How long must compressed air health records be kept?

Health records and exposure records must be kept for at least 40 years. This allows health effects that appear later to be linked back to the work.

When is a medical lock required?

Where people work at 0.7 bar or more, treatment facilities must include a medical lock and people competent to operate it and give medical assistance. At 1.0 bar or more, a dedicated person competent to do both is needed.