A review in Diving and Hyperbaric Medicine compared the bell excursion procedures of 13 commercial saturation diving companies with the US Navy, Comex, French, Brazilian and Norwegian reference tables. Companies have cut routine excursion distances to around 40 to 60 per cent of the 1977 US Navy allowances, decompression sickness linked to excursions is now rare, and most changes were made without new scientific evidence. For diver medic technicians and offshore medics supporting North Sea diving, it explains where today’s rules come from and where the gaps are.
Why this matters
Saturation diving keeps divers under pressure for weeks at a “storage depth”, also called living depth, in a chamber on the vessel. They travel to the worksite in a diving bell and may work shallower or deeper than storage depth. These depth changes are called excursions. An upward excursion is a small decompression. A downward excursion loads extra inert gas that must be dealt with later.
Heliox, a helium and oxygen breathing mix, is standard for this work. Each company sets its own excursion limits, oxygen levels and rest periods in its diving manual. The authors asked where these rules come from, how much they differ, and whether the evidence supports them.
The last large validation studies date from the 1960s to 1980s. Since then, companies have adjusted the tables through experience rather than trials, and they do not share incident data. The current rate of decompression sickness (DCS) after excursions is therefore hard to measure.
What the researchers did
Six authors led by Jean-Pierre Imbert of Divetech, France, with Philip Bryson of TAC Healthcare Group, Aberdeen, as corresponding author, published the review in March 2026 (volume 56, issue 1, pages 21 to 40). It follows the group’s 2024 review of final saturation decompression, which left excursions out.
Fifteen companies were invited and 13 took part under a memorandum of understanding. Their diving manuals, revised between 2021 and 2024, were anonymised as Companies A to M and compared with five reference procedures: US Navy Diving Manual 2016 (Revision 7), Comex 1994, France’s MT92, Brazil’s Normam-15 (2016) and Norway’s NORSOK U-100 (2023).
They compared design concept, depth range, excursion limits, oxygen partial pressure (PO2) in storage and in the diving mix, ascent rates and post-excursion holds. They also traced the tables’ history to the early 1960s and gathered published DCS and bubble data. The study had no funding. The authors work in the offshore industry, some for participating companies.
What they found
Two designs dominate. The US Navy approach enters the table at the deepest depth reached in the previous 48 hours. The Comex approach uses storage depth after an eight-hour window. Ten companies use US Navy-derived tables and four Comex-influenced tables, one drawing on both. Newer refinements include extended excursions and a “sliding window” allowing work above and below storage depth.
Distances vary widely. From a storage depth of 120 metres of seawater (msw), the US Navy 2016 table permits a 32 msw descending excursion. Comex 1994, MT92, Brazil and NORSOK all allow 12 msw. Comex standard excursions are 39 to 43 per cent of US Navy distances and NORSOK’s 37 to 38 per cent. The authors describe a consensus of 40 to 60 per cent of the 1977 US Navy distances for routine work and 70 to 75 per cent for exceptional extended excursions.
Oxygen settings are more uniform. Storage PO2 sits between 0.35 and 0.50 bar and diving mix PO2 between 0.50 and 0.90 bar. Most companies hold eight hours after the last excursion before final decompression, with a range of two to eight hours.
Safety data are reassuring but old. The Comex database for 1977 to 1994, covering around 1,000 man-saturations and 20,000 bell dives a year, recorded two inner-ear DCS cases immediately after excursions, in 1984 and 1985. Overall DCS during or after final decompression was 0.54 per cent, all pain-only. The Seaway Hades database reported 0.83 per cent (22 cases in 2,662 decompressions), none after an excursion. Norway’s regulator has recorded no excursion-related saturation DCS since 1990. The authors also list four North Sea inner-ear DCS cases between 1992 and 2000, each immediately after a US Navy-compliant excursion of 17 to 22 msw.
Excursions rarely cause immediate symptoms but may add to bubble load during final decompression. A Danish sector study found no venous gas emboli one hour after descending excursions from 37 to 45 msw. Current PO2 values are unlikely to cause pulmonary oxygen toxicity. Deeper than 200 msw, excursions have been linked to high pressure nervous syndrome, mainly hand tremor, and distances there are limited to 15 msw.
Strengths and limitations
This is the only published side-by-side comparison of current commercial excursion procedures, and it includes the major North Sea contractors.
It is a document review, not a clinical study. Only manuals were examined, and companies did not share DCS data, so the authors cannot state a current incidence. Much of the history rests on the authors’ personal experience. The DCS databases are decades old, and under-reporting of mild symptoms is possible. The authors declare industry links and describe the review as independent.
The findings transfer well to UK practice. Participating companies operate in the North Sea, and the report explains the lineage of the tables UK diver medics see every day.
What it means for your practice
- Diver medic technicians: know which design your employer uses, deepest-depth or storage-depth, because it decides how a missed limit is assessed. Inner-ear DCS has followed excursions within table limits, so treat vertigo, hearing loss or nausea after return to storage depth as an emergency and inform the supervisor and diving doctor at once.
- Offshore medics: know your company’s post-excursion hold and record excursion depths and times in your handover. Joint pain late in decompression may relate to earlier excursions.
- Paramedics and first responders: saturation divers are treated inside the chamber system, not evacuated to shore. Your role is support and liaison. Do not manage pressure-related problems outside your scope.
- Do not change any excursion limit, PO2 setting or hold period on the basis of this review. Company procedures, IMCA guidance and the appointed diving doctor govern practice. For onshore care, JRCALC applies.
Reflect
- Which excursion design does the contractor you support use, and where in its manual are the limits and holds set out?
- How would you recognise and escalate inner-ear DCS in a diver who has just returned to storage depth?
- What information about recent excursions should appear in your handover before final decompression begins?
- How does the lack of shared industry DCS data affect your confidence in current procedures?
Read the original
- Diving and Hyperbaric Medicine, Review of excursion procedures used in commercial heliox saturation diving, 2026
- Diving and Hyperbaric Medicine, Review of saturation decompression procedures used in commercial diving, 2024
- Norwegian Ocean Industry Authority (Havtil), Report on compression and excursion parameters for saturation diving, 2024
- Health and Safety Executive, RR244 Excursion tables in saturation diving: decompression implications of current UK practice
Published 25 October 2026. Last reviewed October 2026.
These summaries are for education and CPD only. They are not clinical guidelines. Always practise within your scope of practice and follow your employer’s protocols and national guidance such as JRCALC and Resuscitation Council UK.