Review of saturation decompression procedures used in commercial diving

Abstract

Introduction: This is a review of commercial heliox saturation decompression procedures. The scope does not include compression, storage depth or bell excursion dive procedures. The objectives are to: identify the sources of the procedures; trace their evolution; describe the current practice; and detect relevant trends.

Methods: Eleven international commercial diving companies provided their diving manuals for review under a confidentiality agreement.

Results: Modern commercial diving saturation procedures are derived from a small number of original procedures (United States Navy, Comex, and NORSOK). In the absence of relevant scientific studies since the late 80's, the companies have empirically adapted these procedures according to their needs and experience. Such adaptation has caused differences in decompression rates shallower than 60 msw, decompression rest stops and the decision to decompress linearly or stepwise. Nevertheless, the decompression procedures present a remarkable homogeneity in chamber PO₂ and daily decompression rates when deeper than 60 msw. The companies have also developed common rules of good practice; no final decompression should start with an initial ascending excursion; a minimum hold is required before starting a final decompression after an excursion dive. Recommendation is made for the divers to exercise during decompression.

Conclusions: We observed a trend towards harmonisation within the companies that enforce international procedures, and, between companies through cooperation inside the committees of the industry associations.

Keywords: Decompression tables; Occupational diving; Saturation diving.

Figure 1

A typical commercial diving saturation showing depth profile and divers inhaled partial pressure of oxygen (PO₂); mbar – millibar

Figure 2

Age distribution of 131 saturation divers working on a large North Sea diving support vessel

Figure 3

Decompression times in decimal hours for several typical storage depths, for the company procedures reviewed; the predecompression hold is excluded from the decompression time. std – standard

Figure 4

Daily decompression rate (msw·day^-1) versus depth (msw), for the 11 different procedures analysed

Figure 5

The ‘W’ rule used for storage depth adjustments during one saturation