Diving Risk Factors

Scuba diving is, statistically at least, a fairly safe pursuit.  High quality training and practice can go a long way to ensuring a diver never needs the attention of emergency hyperbaric services such as ours.  That said, accidents and plain bad luck do of course still happen.  Based on what we see, some specific diving risk factors are worthy of a mention:

Medical issues can play a big part in the increased risk of decompression illness.  A significant number of cases of decompression illness we see are related to the diver having a Patent Foramen Ovale (PFO).  This heart condition can, depending on the size/type/characteristics of the opening, increase the risk of decompression illness for a diver.

More information about specific medical issues and fitness to dive queries can be found in our Diving Medical Questions section.  As a general rule, be aware that:

Any dive performed where compressed gas is breathed requires the ascent to surface to be carried out in a controlled manner, allowing dissolved gases to be expired safely through the lungs (the effect of Henry’s Law) and avoiding over-expansion of the lungs (the effect of Boyle’s Law).

Training organisations recommend different ascent rates, typically from 6 to 9 metres a minute. Dive computers often vary recommended ascent rates according to the dive profile and the current depth. Some divers follow their smallest bubbles to gauge the ascent rate.

Whichever method is used, the final 10 metres to surface is crucial – due to the pressure halving and volume increasing by a factor of 2. An uncontrolled ascent in this range is likely to cause problems if:

As with ascent rates, many different recommended dive tables and decompression algorithms are in use. Originally the timings were developed by observing people working under pressure. Later changes were made based upon experimentation and theories based on gas exchange in the body.

Whether a table or computer is used, the decompression schedule is designed to allow the diver to control decompression. Greater dive depths and longer bottom times increase gas loading, requiring longer decompression and potentially increasing risk, particularly if decompression stops are then missed following a problem.

Multiple dives will of course increase gas loading as well and your dive computers will take this into account when calculating your decompression requirement.  In some cases the dive computers are also measuring your gas consumption and adjusting decompression accordingly.  Bear in mind that if your dive computer does not have this option that your decompression stops are based on a model Average Diver.

In the UK the environmental conditions are a significant factor, even in the summer months.

It is important to get an accurate weather forecast before the dive to assess the likely conditions. Choppy sea states can affect some and sea sickness can lead to dehydration, increasing the risk of decompression illness.

Poor underwater visibility is not unusual, particularly if silt is disturbed. Disorientation and confusion in such conditions can happen very quickly. Cold conditions can affect co-ordination and impair operation of equipment. Fog presents an additional hazard, hindering diver recovery and the ability of the emergency services to assist in the event of an incident.

Tidal conditions can cause real difficulty in completing decompression schedules safely.

All of the above conditions have contributed to divers requiring recompression treatment.

Sea-sickness, dehydration and fatigue can be contributory factors in the risk of decompression illness.  Each individual’s circumstances and fitness to dive should be taken into account when planning a dive.

To reduce your individual level of risk of decompression illness following a dive, ensure that: