Safe Diving B
| Boats |
| BSAC 88 deco tables (Air and nitrox diving) |
| Buddy diving |
| Buddy lines |
| Building experience |
| Build-up dives |
| Buoyancy |
| Buoyancy compensators |
| Buoyancy compensator cylinders |
| Buoyant ascents |
Boats
Ensure your boats operate at slow speed in any area where divers are below. Those in the boat should keep close watch for divers surfacing unexpectedly.
When dropping divers into the water, or retrieving them, ensure the engine is in neutral, and that they are well clear of the propeller before you engage gear. All boats should be marked for easy identification by the rescue agencies and should be properly equipped before taking them to sea, in accordance with BSAC guidelines.
Boats used on BSAC events must have appropriate third party insurance cover.
When using boats take note of the recommendations for boat users laid down in the Diver's Code of Conduct and the document “Guidelines for Safe Operation of Member Club Boats�.
BSAC 88 decompression tables (Air and nitrox diving)
The NDC considers the BSAC 88 Tables to be safe sports diving tables and recommends their use. The BSAC 88 Tables, Levels 1-4, have been specifically designed for sports diving on air and nitrox and to help divers avoid decompression illness.
The Tables promote safer diving practices, particularly by encouraging slow, controlled ascent procedures (15m/min) and allow divers to make allowance for atmospheric pressure changes due to weather or changes in altitude. Due to the wide variations in human physiology and the large number of factors that can affect your susceptibility to decompression illness, no table can guarantee to protect you against all risk.
Whenever diving the following advice should be taken into account:-
- The maximum recommended depth for recreational diving, when using air, is 50m. Specific depth restrictions, appropriate to skill level and experience, are applicable to some BSAC diving grades (see Depth). When carrying out two or more dives in one day, perform the deepest dive first.
- It is recommended that no more than 3 dives be performed in any 24 hours. Any dive series involving consecutive days diving to 30m+ should be limited to three days, after which a 24 hour break should be taken.
- Always be in control of your buoyancy, especially during the ascent, and observe the recommended ascent speeds.
- It is permissible to conduct slower descents and ascents, whilst remaining within the dive profile envelope, but multiple 'saw tooth' ascents and descents should be avoided.
- Be aware that smoking, alcohol consumption, tiredness, age, increased body fat and any medical condition affecting the respiratory or circulatory systems may increase your risk of decompression illness. Susceptibility can also be increased with excessive physical exertion during or immediately after a dive.
- When diving with nitrox use the BSAC nitrox table or an established air or nitrox computer or software to determine the safe limits for your planned dive. (See Depth and Nitrox).
- When diving with trimix, or other mixed gases, the dive should be planned using an established mixed gas decompression table, computer or software. (See Depth and Mixed gas)
Buddy diving
All divers should train to be self-sufficient; however, it is important for safe diving that divers are formed into appropriate buddy pairs. Buddy diving means a pair of divers operating as a unit, each taking some responsibility for the safety of the other. On every dive one diver, usually the senior in grade or experience, should be elected as the dive leader. Divers with a minimum grade of Club / Ocean Diver may dive together at the discretion of the Branch Diving Officer. Divers below the grade of Club / Ocean Diver (i.e. divers under training) must be led by a qualified instructor or an Assistant Diving Instructor.
A full buddy check should be carried out prior to entering the water.
When snorkelling, dive alternately so that the snorkeller underwater is covered by their buddy at the surface.
Buddy lines
In conditions of poor visibility, you may wish to use a buddy line to retain contact with your buddy. A line two to three metres long is ideal, with a quick release shackle or small karabiner spliced to each end. This allows it to be looped over wrists, if so desired, or it can be clipped to a suitable piece of equipment e.g. BC, to leave both hands free.
Building experience
The BSAC strongly recommends that newly qualified divers undertake a structured series of dives to progressively build their experience. Subsequently, when completing more advanced training, in particular a mixed gas-training course, the BSAC recommends that dive experience in those aspects should again be built up progressively.
Build-up dives
When a diver has had a lay-off from diving for a period of time, or is planning a dive to a depth significantly deeper than that to which they have recently dived, a planned program of dives progressively building up to the target depth is recommended. A diver must be physically and mentally dive fit for the depth he or she plans to dive.
This is particularly true of self and buddy rescue skills, which by their nature, are the least regularly used. They should also be revised whenever any change is made to the equipment configuration, such as when a new drysuit or BC is being used or when additional equipment is to be carried to cater for mixed gas diving.
Buoyancy
Buoyancy is one of the key issues involved in decompression Illness incidents. All divers should ensure that they:-
- Have sufficient buoyancy to be supported on the surface.
- Are practiced and confident at performing decompression stops within +/- 0.5m.
- Are able to maintain neutral buoyancy and maintain a depth level at all stages of the planned dive.
- Are able to control their ascent rates within recommendations.
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Are proficient in managing emergency buoyancy control scenarios, e.g., over inflation, loss of primary gas, faulty equipment, etc.
Buoyancy compensators
Divers need to be able to adjust their buoyancy underwater to compensate for buoyancy losses due to pressure changes on descent, and then to reduce this buoyancy as they ascend. This may be provided by inflation of a drysuit or by means of some buoyancy compensating device. Total reliance on a drysuit is not sensible and a suitable buoyancy compensator (BC) should be worn on every open water dive.
There are three main types of buoyancy compensator currently on the market, the Adjustable Diving Vest (ADV), the Stabiliser Jacket (STAB) and the 'wings' style of BC.
Most are made in various sizes and care should be taken to choose the correct size and amount of buoyancy offered. All buoyancy compensators must have a direct feed mechanism for routine buoyancy adjustment.
The diver's other requirements for a buoyancy system are to stay afloat at the surface or to give emergency buoyancy whilst rescuing or being rescued. An inflated drysuit is not a good solution in these surface situations and drysuited divers must wear a buoyancy compensator to maintain and control positive buoyancy safely.
Divers should minimise the number of buoyancy systems in use at any given time during the underwater phase of the dive. When wearing a dry suit it is recommended to use the drysuit only to compensate for loss of buoyancy due to compression at depth and change over to the BC for positive buoyancy at the surface.
Buoyancy compensator cylinders
Some buoyancy compensators can be fitted with a small air cylinder for emergency inflation. These cylinders need to be tested / inspected at the same interval as larger diving cylinders. (See Cylinders). Never overcharge a cylinder and avoid storing one for any length of time fully charged. Ensure that the working pressure of the BC cylinder is compatible with the working pressure of the aqualung cylinder. Avoid completely emptying such cylinders since, if the valve is allowed to remain open, any water in the buoyancy jacket or moisture from the atmosphere, may be drawn into the cylinder.
It is strongly recommended that BC cylinders should not be filled with enriched air (nitrox) mixtures.
Buoyant ascents
These fall into two categories, buoyant ascents in an emergency, and controlled buoyant ascents in a non-urgent situation. In the former it is vital to remember the risk of embolism and positive breathing out is absolutely essential. In the latter case, the training programme teaches the correct techniques to ensure a safe ascent rate in a controlled manner. It is most important that an ascent rate of 6 metres per minute is achieved from 6 metres to the surface and this requires that the diver is always capable of being neutrally buoyant at 6 metres with a near empty cylinder.
Page last modified: 12th Dec 2006 - 15:32:12