BSAC Technical Publications - Safe Diving Practices A-C LEARNING TO DIVE MEMBER SERVICES TECHNICAL SERVICES FORUMS BSAC WORLD SNORKELLING MAIL SHOP NEWS TECHNICAL SERVICESSearch the BSAC Site: sitemap BSAC TECHNICAL PUBLICATIONS SAFE DIVING PRACTICES A - C D-H | I-P | Q-Z | Code of Conduct | Rebreathers Access/Egress Ensure that your access to the water is safe and that you can successfully regain contact with your boat/beach/shore. Always ensure, when diving from the land, that it is possible to climb out at the planned exit point at varying states of the tide. Accidents/Incidents Any member involved in a diving accident or incident should notify BSAC HQ. An incident report form will then be sent, which should be completed and returned as soon as possible. Reports are treated as strictly confidential and are used to prepare an analysis of safety performance each year. If there is any possibility of a third party insurance claim arising out of the circumstances it is particularly important that a form is completed without delay. Air Reserve Always ensure you have an adequate reserve of air (at least 25% of cylinder(s) capacity is strongly recommended) at the termination of a dive. The amount of air deemed to be an adequate 'reserve' will obviously depend on a number of factors including the size and working pressure of your main cylinder together with the depth and type of the dive - a standard figure is not appropriate. The reserve should be sufficient for a normal ascent, plus any decompression stops, and to allow adequate amounts for surface swimming. Remember that rates of air consumption can vary enormously with the effects of cold, fitness, exerience and depth and you should monitor your own and your buddy's air supply regularly. Alternative Air Sources (AAS) The BSAC strongly recommends that all divers carry an alternative air source (AAS) in the event that they may need to share air underwater. Suitable AAS include an 'Octopus Rig' (a second 2nd stage fitted to the same 1st stage of the regulator, which includes the type fitted to a direct feed). In this case divers should be aware that a first stage failure on their regulator will affect both second stages and render them in-operative. A more strongly recommended alternative, however, is a totally independent air supply such as a 'Pony cylinder' (a small 2-3 litre auxiliary cylinder attached to the main cylinder with its own regulator assembly) or separate regulators attached to each cylinder of a matched pair. If a manifold is fitted to the pair of cylinders, making them into a 'twin-set', it should allow the diver the ability to isolate each cylinder/regulator assembly should a failure occur. Auxiliary cylinders having a capacity of less than 3 litres and ABLJ/BC mouthpieces are not considered adequate AAS. Altitude Diving at altitude, or travelling to altitude (including flying), either before or after diving, involves the diver being exposed to a reduced atmospheric pressure. This can both affect the decompression procedures required and increase the diver's susceptibility to decompression illness. The BSAC 88 Decompression Tables, Levels 1-4, have been specifically designed to allow the various factors involved to be taken into account in a simple manner. They should be used for all dives at altitude and also for determining whether a particular dive/journey sequence involving an excursion to altitude is permissible. (See BSAC 88 Decompression Tables). Ascent Rate Maintaining a safe rate of ascent is vitally important in preventing possible decompression illness and the risk of gas embolism. The BSAC 88 Decompression Tables have been calculated on a maximum ascent rate of 15 metres per minute up to 6 metres depth and 6 metres per minute from 6 metres to the surface and this must be adhered to when using the tables. Some dive computers incorporate slower ascent rates of 10 metres per minute but all divers are recommended to follow the practice of ascending at 6 metres per minute from 6 metres to the surface. Repeated multiple ascents should be avoided as they may result in decompression illness. Particular care should be taken when carrying out the various ascent training drills, for which specific advice is available. 'Sawtooth' dive profiles which involve repeatedly ascending and redescending over an uneven bottom should be avoided, but the practice of returning to the surface from maximum depth in stages is encouraged. Assisted Ascents The National Diving Committee strongly recommends the use of an alternative air source (see Alternative Air Source) as the prime method of assisted assent, and that all divers should carry such equipment. Authorised Branch Dives An authorised dive by a BSAC Branch is one carried out with the prior knowledge and approval of the Branch Diving Officer. A properly qualified and appointed dive marshal shall be present and shall be in charge of all diving activities for the duration of the dive/expedition. All Branch dives should be carried out in accordance with current BSAC rules and recommendations for safe diving. AV (Artificial Ventilation) and CC (Cardiac Compression) When demonstrating or practising AV in the water, a proper seal (usually nose) should be made. A simulated seal is not sufficient to give the sense of realism required, and does not guarantee a successful acquisition of technique. The use of a manikin is strongly recommended when practising AV on land. Cardiac Compressions (CC) should never be practised on a conscious breathing subject, a manikin should always be used. The following rates for AV & CC are recommended:- AV on land. The rate of ventilations should be judged by monitoring the rise and fall of the casualty's chest and the sound of the casualty's exhalations. When in water - 2 breaths/15 sec. CC 100 compressions/1 min. Combined AV and CC - 2 breaths/15 compressions. 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 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. BSAC 88 Decompression Tables The NDC considers the BSAC 88 Tables to be the safest sports diving tables available in the world and recommends their use. The BSAC 88 Tables, Levels 1-4, have been specifically designed for sports diving on air and incorporate new thinking on the avoidance of decompression illness. The Tables promote safer diving practices, particularly by encouraging slow, controlled ascent procedures and allow divers for the first time 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. (15m/min to 6m and 1 min from 6m to the surface). 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 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. (See Depth and Mixed Gas) Buddy Diving 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. 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 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. BCD, to leave both hands free. Buoyancy Compensators (BCD) Divers need to be able to adjust their buoyancy underwater to compensate for buoyancy losses due to pressure changes on descent, and then to jettison 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 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 BCD. 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 buoyancy safely. 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 (Air) below) 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. Compressors For safety reasons only properly trained and competent people should operate compressors. If you use a portable petrol or diesel engine take care not to have the air intake in a place where fumes may be ingested with the air, and never use the compressor in a site where it is an annoyance to other people. It is essential that air of a high standard of purity is delivered. The production of compressed air for use in oxygen enriched mixtures requires specialised oil-free equipment and training. Only properly trained operators using appropriate equipment should undertake this. (See Nitrox) Computers Dive computers offer accurate and automatic recording of depth and time and continuously calculate the diver's decompression requirements according to the depth and duration of the dive. Computers are also available with advanced features such as the ability to calculate decompression requirements for a variety of Nitrox mixes and mixed gases, and also to monitor available air and air consumption rates. The use of a dive computer is no subtitute for proper dive planning, including proper attention to air requirements and dive time. It is recommended that divers choose a computer which is at least as conservative as the BSAC 88 Decompression Tables on a rectangular dive profile. Individual susceptibility to decompression illness varies and can be affected by a number of factors, for which no computer or decompression table is able to allow. Divers should be aware of this and avoid pushing computers beyond their limits. The advice on safer diving attached to use of the BSAC 88 Tables applies equally to computer users and should be followed. (See BSAC 88 Decompression Tables) Cylinders (Air) Air cylinders to the obsolete specifications HOS, HOT (steel) and HOAL 1, 2, 3, and 4 (aluminium) are still legal for use by divers, although no longer manufactured. Test standards BS 5430 Part 1 & 3 have been withdrawn. The current test and inspection specifications (August 2002) approved by the Health and Safety Executive are BS EN 1968 (Steel) and BS EN 1802 (Aluminium). Diving cylinders must be tested according to the aforementioned standards. These standards call for diving cylinders to be visually inspected every TWO & a HALF years and subjected to a hydraulic test every FIVE years. Divers should ensure that test stations carry out their tests in accordance with BS EN 1968 and BS EN 1802 and should obtain a test certificate which states this. Test stations approved by the Inspectorate for Diving Equipment Servicing and Testing (IDEST) are recommended. The cylinder should be stamped by the test station after every inspection / test and a label attached to indicate when the next inspection is due. Cylinders (Nitrox and Mixed Gas) Cylinders for use with Nitrox and Mixed Gas should be dedicated to this use, marked with a suitable label that clearly identifies the gas mixture contained (oxygen percentage) and the Maximum Operating Depth (MOD). Cylinders should be regularly (usually annually) cleaned to oxygen service standard. Oxygen service standard is essential where the oxygen content is 23% or greater and the cylinder is likely to be filled using pure oxygen and the partial pressure method. Nitrox cylinders should have a maximum working pressure of 250 bar. Cylinder contents should always be analysed at the time of filling and again immediately prior to the dive (See Nitrox and Compressors) A-C | D-H | I-P | Q-Z OTHER BSAC TECHNICAL PUBLICATIONS ©2003 BSAC | Home Page | Member Services | Technical Services | News