Safety Talk Last Month
We are not meant to be here As all divers are aware, diving is not a simple undertaking. There are few, if any, other We are able to enter this environment because of the specialist equipment we use and the equally specialist training we receive in the use of it. Even then, should something go wrong, we are immediately at risk from that alien environment (in skydiving for example a parachute failure is not immediately life threatening until you get to the sudden stop at the end!). As a consequence additional equipment and training is also required to help us cope (and survive) such situations. Even allowing for the equipment and training there are very clear aspects of the underwater environment that add further complications that compel us to take them into consideration, not least the gas we breathe. activities that we can undertake that allow us to enter an entirely alien environment and not only survive (a great start) but also to actually enjoy the experience as well!
Survival
All animals require oxygen as an essential component of life. Different groups within the animal kingdom have evolved to obtain that essential oxygen from different sources and whilst fish and other marine creatures can obtain what they need from the water they are in, we on the other hand require our oxygen from the air (gas) we breathe.
Air
The natural assumption for the pioneer divers is that carrying the same gas (air) with us, either on a breath hold dive or in scuba equipment, would seem a logical choice? However, it soon became apparent that air is completely the ‘wrong’ gas for divers. Increasing depths have the effect of making inert gases both narcotic and giving us decompression problems. Continue going deeper and even the oxygen becomes a problem. In fact about the only gas that doesn’t give us a significant problem with increasing depth is our waste product CO2. So what is the solution?
Nitrox
A simple first step would be to replace some of the nitrogen with another gas, the most readily available being oxygen. Reducing the nitrogen component serves to reduce the nitrogen decompression requirements. Even at entry level qualification limits (18-20m) reducing the nitrogen loading can only make diving safer. The side benefit of including it also means that divers understand a little more about the effects of diving gases. As a result BSAC incorporated Nitrox training within the entry level qualifications of Ocean And Sports Diver in 2007.
Mixed Gas (Trimix)
Sadly Nitrox alone is not the answer. Increasing the oxygen percentages increases the risks associated with oxygen toxicity at shallower depths. Reverting back to air for deeper dives (>40m) may reduce the oxygen toxicity problems but makes the narcotic effects of nitrogen increasingly more significant just at the point where effective decision making becomes increasingly critical. The answer is to replace the nitrogen and potentially the oxygen as well with a less narcotic gas but still carries a, potentially more complex, decompression profile.
The consequence of all this is that there is a need for yet more training, specialist equipment and even then we are still often faced with a compromise. However, we have the increased understanding to allow us to make informed decisions about our safety.
Think SAFE – Dive SAFE
Jim Watson, BSAC Safety and Development manager
Top Safety Tip 6
Stay within Depth Limits
Top Safety Tip 8
Maintain Equipment
Top Safety Tip 10
Don't dive solo
Top Safety Tip 7
Carry Location Aids
Top Safety Tip 9
Report Incidents
