Caisson Worker

Hyperbaric Medicine

Recreational diving



Hyperbaric Shuttle
at Westerschelde

Hyperbaric Shuttle
Saint-Petersburg Metro


Shuttle and Pre-chamber
during commissioning

Hong Kong
Shuttle handling


Caisson workers are also called Compressed Air Workers.  Most of their interventions are digging tunnels under pressure or inspection & repair under pressure the TBM cutter heads, standard caisson works, inspection of Nuclear Power Plants (for 10 years pressure/leak tests) and leak testing of airplanes cabin upon delivery.

The concept of compressed air work must be extended to compressed gas works since mix gases breathing have been used in tunnelling operations since 2002.

JCLP HYPERBARIE may take care of :

  • Design, construction follow up, commissioning of compressed air work plant and equipment, either for the account of the final user, either for the TBM manufacturer, frequently in close cooperation with both.
  • Writing operation procedures and safety manuals and obtaining approval by local authorities when required. 
  • Training all personnel  involved (Site director, Hyperbaric operation superintendents, Lock operators, compressed air workers (French Certificate Hyperbariste Mention D Classe I, II - approved by the French Ministry of Labor), Welders and arc-air operators under pressure.
  • Safety follow up of operations throughout the works and adapt organization to unexpected situations (Polluted area, heavy duty repairs under pressure, arc-air and welding, changes in procedures (oxygen decompression) eventually change the air lock system for a new one...!
  • Negotiate with local authorities dispensations when legal local requirements are obsolete for TBM work under pressure (USA, Australia, Hong Kong ....).
  • Providing decompression procedures for Trimix interventions bounce and saturation (4 bars to 7 bars)
  • Assistance for French Hyperbaric Certification of tunnel building companies (2020)
  • Consulting for standardisation of airlocks for tunnelling

References :

Since 1986, JCLP HYPERBARIE has been involved with more than 90 tunnel construction sites with operations in compressed air, for all French contractors who have built tunnels with compressed air, and with most of European and North American TBM manufacturers.
  - Metros : Lille (4 sites), Météor, Eole, Rennes, Cairo (2 sites), Lisbon (3 sites), Madrid, Copenhagen, Strasbourg, Rouen, Sydney, Lyon (3 sites), St Petersburg...
  - Road Tunnels :  Théo (Lyon), Westerschelde (The Netherlands), El Ahzar (Cairo), Socatop (Paris),
  - Train Tunnels : Villejust, TransChannel, KCRC 320 in Hong-Kong, Groenehart TGV tunnel in the Netherlands, HK 201, Napoli-Bari Treno Alta velocità. 
  -  Sewage : Many sites in Paris area, Toulouse, Bordeaux, Lyon, Swansea...
  - Technical Tunnels : Berlin (3 sites), Paris...
  - Nuclear Power Plants : Writing the safety specifications for hyperbaric inspections of Nuclear reactor buildings (National French Electricity Board - EDF)

- Training of plane inspectors for hyperbartic leak testing (Airbus Industries)

- Hypobaric (0,70 bar absolute) visit of plane fuel tanks for leak detection (Air France)


The range of pressures are from 0.6 bar(a) to 6.9 bar(g). The more frequent pressure range is between 1.8 to 3 bar. 
Between 4.5 and 6.9 bar, helium containing breathing mixtures and saturation procedures have been specially developed and used at Westerschelde Tunnels in The Netherlands June/September 2000 - refer to publication,  and for Saint Petersburg Metro in 2002/2003 - (for 6 bar bounce interventions).

A full set of procedures has been developed and the corresponding equipment has been built to support Hallandsas Tunnels digging in Sweden where possible pressure may have reach 13 bars. (2004). Ultimately not used...

Similar work has been performed with Traylor, then with Impregilo for the tunnel below lake mead in Nevada (USA) for 15 bars; Ultimately not used !

Calculation of all tables for Trimix bounce interventions (Hong Kong, Seatlle, London - HTMS) and Saturation procedures for Hong Kong saturation 6 bars, with Hyperbarie Sarl (2015)

Special situation : Digging under compressed air in a kerosene contaminated soil (refer to publication)

Negotiation with authorities to obtain specific dispensations has been carried out in Australia, Hong Kong, Germany, Spain and Portugal

JCLP HYPERBARIE has also been the Consultant for the French Ministry of Labor for almost 10 years (1987/1996), he is a member of  Working Groups in AFTES "Compressed air works" and for CEN (151 WG 4 :  Safety Standard for TBM- air locks - EN 12100and 2023 revision).


   Airlock for Bari-Naples TAV tunnel digging (2023)