DMAC22
DMAC22
DMAC22
Introduction
In the preparation of this guidance, which is specific for locations where a compression chamber is on
site, the Committee has used its judgement to propose a reasonable compromise between the time required to
remain at a chamber location against the progressively diminishing risk of developing acute decompression illness.
Consideration has been given to the evidence available from reported incidents in the North Sea, naval sources,
the experience of major diving contractors, and relevant papers in the scientific literature. Types of diving differ
very much in their decompression risks but a serious incident can arise after any exposure to pressure, no matter
how safe it may have seemed. Little distinction has been given in the reviewed references to the details of the type
of diving or decompression.
In this note it is assumed that only well proven procedures and tables are being used. After most diving, 95% of
the manifestations of decompression illness arise within 4 hours and, after surfacing from an oxy-helium saturation
dive, symptoms tend to appear within 6 hours of surfacing, but it is not possible to define the point in time after
which there is effectively a zero risk: traditionally this has been set at 36 hours but there are exceptions.
Fortunately, it seems to be generally true that the more serious varieties of decompression illness, which require
an immediate recompression, arise fairly soon after surfacing whereas the manifestations arising six or more hours
after surfacing usually, but not always, require less urgent treatment. Decompression illness may be rare after
relatively shallow dives and the onset of manifestations some 12 hours after surfacing may also be uncommon but,
when it is required, the need for recompression could be urgent. This must be considered in the preparation of
contingency plans.
It is stressed that this note is advisory only and must be considered by each diving contractor's safety and medical
advisers according to the circumstances of each planned dive and the resources which will be available.
The views expressed in any guidance given are of a general nature and are volunteered without recourse or responsibility upon the part of the Diving Medical Advisory Committee,
its members or officers. Any person who considers that such opinions are relevant to his circumstances should immediately consult his own advisers.
Proximity To A Two-Compartment Recompression Chamber
after Surfacing from Air or Mixed Gas Dives
Attention must be given to the separate guidance offered on flying after diving (DMAC 07).
The diving contractor's diving rules should make provision for any subsequent emergency procedures after these
intervals.