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Safe Diving Practice
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| 1 Introduction | ||
| The OUUEG safe diving practices document evaluates the risks inherent in SCUBA diving. All members of OUUEG are given a copy of the BSAC Safe Diving Practices booklet (Ref: 1.2.3), which details safe diving practices and compliments this document. | ||
| 1.1 Definitions | ||
| The following definitions are used in this document. Other useful definitions are found in the references. | ||
| 1.1.1 Buddy | ||
| When diving, one should dive with another suitably qualified diver. This is known as a buddy pair. The buddy pair should dive as a team, assist each other and take care not to become separated. Each diver becomes part of the others safety mechanism. Solo diving is not to be undertaken within OUUEG. | ||
| 1.1.2 Diver Grades | ||
| Definitions of Diver Grades are found in the Branch Officers Handbook. | ||
| 1.1.3 Instructor Grades | ||
| Definitions of Instructor Grades are found in the Branch Officers Handbook. | ||
| 1.1.4 Trainee | ||
| A diver, at
any qualification level who is being taught or assessed by an Instructor.
This training may take place in a classroom, pool, sheltered water or open
water |
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| 1.2 References | ||
| The following documents have been used as references for the OUUEG Safe Diving Practices (SDP). Only the pertinent information has been copied from these references and they should be read, as though included in this document. | ||
| 1.2.1 Oxford University Sports Handbook, Sports Federation, University of Oxford | ||
| 1.2.2 Branch Officers’ Handbook, British Sub-Aqua Club (http://www.bsac.org/page/47/branch-officers-handbook.htm) | ||
| 1.2.3 Safe Diving Practices, British Sub-Aqua Club (http://www.bsac.org/page/45/diving-safety.htm) | ||
| 1.2.4 Code of Practice, Oxford University Underwater Exploration Group (http://www.sub-aqua-images.co.uk/new/codeofpractise.html) | ||
| 1.2.5 Risk Assessment, Oxford University Underwater Exploration Group (http://www.sub-aqua-images.co.uk/new/riskassessment.html) | ||
| 1.2.6 Pool Safety Officers Guidelines, British Sub-Aqua Club (http://www.bsac.org/page/472/pool-safety.htm) | ||
| 2 Underwater Risks | ||
| 2.1 Running out of air | ||
| Running out of air is potentially fatal. Great care should be taken to avoid this situation. Divers should regularly check their own and their buddy’s submersible contents gage (SPG). In the event of an out of air (OOA) situation, special procedures must be in place to reduce the risk involved. | ||
| 1. All divers should carry a second, redundant regulator, commonly called an octopus. This should be offered to the OOA diver as soon as possible. Great care should be taken that this regulator is working, and that each buddy team member is aware of its location and operation. | ||
| 2. Both divers should plan to have enough air reserves to safely get two stressed divers to the surface, observing any required decompression stops, from any point within the dive. | ||
| 3. The octopus should be on a hose of at least 90cm length to facilitate the sharing of air. | ||
| 4. Divers should
take care with equipment configuration to ensure that the octopus regulator
is highly visible and easily deployed. |
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| 2.2 Regulator free-flows | ||
| Regulator
free flows can sometimes happen in cold water, due to mechanical parts of
the regulator freezing. This results in the rapid loss of air via the regulator
mouthpiece, which is almost impossible to stop once started. This can then
result in an OOA situation. Using cold water protected regulators can reduce the risk of free-flow due to freezing. The regulator should not be “breathed from” on the surface, as this can cause condensation to build up in the mouthpiece, which can then freeze. Wait until the regulator and the mouth are underwater before starting to breathe from the regulator. In the event of a free flow, the free flowing regulator must not be switched off. Switching off the free flowing regulator |
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| 1. Leaves the
diver without air should separation occur, and 2. Leaves the diver with no buoyancy. |
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| These
are both potentially fatal problems, and can be avoided by not switching
off the air supply. The divers should make an alternate air-source ascent using buddies octopus regulator. Do not stop and try to fix the free flow underwater, proceed directly to the surface, observing any decompression stops. The air supply may be switched off on the surface, once the diver is made positively buoyant using the BC. |
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| 2.3 Entanglement | ||
| Nets,
ropes and discarded fishing lines are common on many dive sites. All divers
should take care to avoid being entangled in this debris. Surface marker
buoys used to inform the surface cover of a divers whereabouts, and penetration
lines, can also be a source of entanglement. Divers should take care to
deploy and recover line in a safe manner. |
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| 2.4 Separation from surface cover | ||
| All divers should use a surface marker buoy (SMB) wherever possible. If an SMB would cause problems during the dive (i.e. penetration diving) a delayed-SMB must be taken and used on ascent. This enables the boat or surface party to follow the progress of the divers. It also provides surface flotation at the end of a dive should it be required. In the event of separation from the surface party or boat, the dive marshal/coxswain should initiate emergency procedures. The diving pair will not know about separation until on the surface. When arriving on the surface and discovering that separation has occurred, they should: | ||
| 1. Inflate
their BC’s. 2. Remain close together. 3. Consider swimming ashore if possible. 4. Deploy any surface detection aids – e.g. Strobes, flags, flares, torches etc. – as appropriate. |
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| 2.5 Buddy separation | ||
| In
the event of buddy separation, a diver should conduct a brief search for
their buddy. This should take no longer than one minute and consist of 2
360 deg. searches remembering to look above and below. All divers in the
group should then ascend directly to the surface, observing any decompression
stops required. The alarm should then be raised with the surface cover or
boat coxswain. If any divers from the separated team have failed to surface
within five minutes of the first diver surfacing, emergency procedures should
be initiated. |
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| 2.6 Marine life | ||
| There is very little danger from marine life around the British coastline. However, care should always be observed with any wild animals. Crabs and lobster can give a nasty pinch and even break fingers. Seals will bite if provoked, as will dogfish and Conger eels. Jellyfish can sting exposed skin, and care should be taken to avoid touching their tentacles. If a person is injured by a marine animal, then appropriate first aid and medical attention should be sought as soon as possible. | ||
| 3 Advanced Diving Risks | ||
| Special procedures should be observed as the complexity of a particular dive increases. All of the above points should be considered, and additionally, the ones below. | ||
| 3.1 Deep dives | ||
| Dives
deeper than 30 meters require a higher level of planning and equipment redundancy.
The use of “Pony Bottles” as a minimum level of redundancy should
be considered. Divers should pay particular attention to their equipment,
and ensure that it is in good order. Generally speaking, the deeper and
longer the dive, the greater should be the level of redundancy utilised. All divers must carry: |
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| 1. A dive timer
and depth gauge, or a dive computer. 2. A slate for communication and recording the dive plan. 3. A knife or line cutter. 4. A torch. 5. A redundant air source. |
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| Each
pair must have an SMB (delayed or standard) and reel between them, and be
familiar with its use. |
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| 3.2 Decompression diving | ||
| When
planning dives involving more than five minutes of decompression, both divers
must have a suitable level of redundancy. This may be in the form of a Pony
bottle, but ideally would be in the form of twin cylinders. These may be
either be independent or manifolded tanks. The dive plan must formally examine
the possibility of either diver losing all access to air, and having to
decompress and surface using their buddies gas supply. The divers equipment
configuration must enable this to occur safely and to the satisfaction of
all divers involved. Where possible, decompression should be performed on a static shot line. In heavy current, the use of a delayed SMB should be considered. The boat coxswain must be notified of the decompression procedure. It is good practice that all dive pairs/teams observe the same procedures. I.e. all should decompress on the shot line, or all should drift with delayed SMB’s. Any mixture prevents the boat from giving adequate cover to all divers. In cases of high current and long decompression, the use of deco-stations should be considered. Where practical, spare gas should be placed on the decompression line, station or shot line. This will allow divers to safely complete decompression in the event of running low on air. |
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| 3.3 Overhead Environments | ||
| Dives in which a wreck or cave ceiling obstructs the direct route to the surface should not be undertaken without training and a great deal of caution and planning. | ||
| 1. All dives
into the overhead environment should utilise a continuous guideline back
to clear open water. In the case of “swimthroughs” where a different
exit point will be used to that of entry, guideline should still be used
unless regular, constantly visible, points for egress exist 2. Penetration dives must utilise the “rule of thirds” for gas management. One third of the available air should be used for descent and bottom time, one third for ascent and decompression, with the remaining third being kept available as a reserve or bail-out in case the diver, or his buddy, has an equipment failure, or OOA, at the deepest planned point of penetration. Overhead environments should not be entered with less than 150 bar remaining in the diving cylinder. 3. The use of a 200 cm long hose on the donated regulator is highly recommended for this type of diving, particularly should the dive require an “in-line” egress while sharing air. 4. All divers should carry a minimum of two torches. 5. The use of a pony cylinder is highly recommended, with a double cylinder arrangement being preferred. |
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| 3.4 Diving with breathing mixtures other than air | ||
| Nitrox is now a commonly used breathing gas. It contains a higher proportion of oxygen than air, which implies less nitrogen. This means that it offers the advantages of: | ||
| 1. Longer no-decompression
times. 2. Increased safety form the risks of decompression illness. |
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| 3.5 Oxygen toxicity | ||
| The increased percentage of oxygen in the breathing mixture means that oxygen toxicity is a more serious concern than with air diving. I.e. oxygen toxicity is not a concern when diving with air until a depth of 57m, whereas with a 36% Nitrox, the equivalent ppO2 would occur at 28m. Oxygen toxicity underwater is a potentially fatal condition. Its risk can be virtually eliminated by using certain procedures. These are outlined below. | ||
| 1. For the
working portion of the dive, the ppO2 must not exceed 1.4 bar. Careful monitoring
of depth must therefore be performed. 2. A maximum ppO2 of 1.6 is acceptable during decompression if using separate decompression mixtures. 3. All divers using Nitrox must have completed recognised training in its use before undertaking dives using these gases. 4. Due regard to issues of accumulated oxygen toxicity (both CNS and pulmonary) must be observed. |
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| 4 Surface Risks | ||
| 4.1 Decompression Injury | ||
| Decompression illness (DCI) is caused by bubbles of nitrogen forming in tissues of the body, causing the obstruction of blood flow, and other consequential problems. Every dive carries a risk of DCI. Certain procedures should be observed to reduce this risk. | ||
| 1. Dive within
recognised decompression tables, or the information presented by a dive
computer. 2. Do not exceed an ascent rate of 10m/min at any point of the ascent, and take at least one minute to travel from 6m to the surface. 3. Conduct a 3 min safety stop on every dive. 4. Do not dive when dehydrated, excessively tired or unwell. 5. Stay warm on the dive. 6. On a series of dives, take a 24 hr surface interval after three days of diving. 7. Use Nitrox if properly trained and where available. |
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| In
the unlikely event of a diver suffering from DCI, a suitably qualified person
should administer pure oxygen immediately. Medical assistance should then
be sought, preferably from a hyperbaric physician. Local coastguards are
able to connect VHF radios to appropriate medical personnel. Recompression
treatment should be sought at the earliest possible opportunity. |
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| 4.2 Pulmonary barotraumas | ||
| This
is caused by air trapped in the lungs expanding on ascent and tearing the
lung lining. Slow ascent rates and breathing normally at all times should
prevent this from happening. In the event that it does occur, the treatment
is the same as for DCI. Administer pure oxygen and obtain medical assistance
as soon as possible. |
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| 4.3 Other barotraumas | ||
| Barotraumas
to the ears is also possible. This is damage to the eardrum caused by descent
or ascent without clearing the ears. A bust eardrum is excruciatingly painful,
and will cause dizziness and vertigo. This would be a dangerous underwater
condition. The risk can be minimised by clearing the ears frequently and
not using force to do so, as this can exacerbate the problem. Diving with
a cold will reduce the ability of the ears to “clear” and should
not be done. |
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| 4.4 General injuries while on the surface | ||
| Injuries can be caused to surfacing divers by boats, particularly in popular tourist areas where there is much boat traffic. All divers should surface directly underneath their SMB. They should also look around, and listen for engine noises just before surfacing. They should be prepared to make a rapid descent out of danger if any nearby boat activity is suspected. | ||
| 5 Dive Boats | ||
| 5.1 Rigid Hull Inflatable Boats | ||
| OUUEG possesses two seaworthy rigid hull inflatable boats (RHIB’s). These craft are inherently buoyant, and almost impossible to sink. They utilise out board petrol engines for power. In order that the coxswain can deal with any scenario, the following items must be carried on every boat. | ||
| 1. Working
VHF radio. 2. Compass 3. Anchor and sufficient line. 4. Sufficient petrol and oil for the return journey plus one half again. 5. Working oxygen kit, with enough O2 for two divers for the journey back to shore and transfer to an ambulance, helicopter or hyperbaric chamber. 6. First aid kit. 7. Tool kit. 8. Flares. 9. Oars. 10. Dive “A” flag. 11. Drinking water. |
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| Before
embarking on any journey, the coxswain of the boat should leave information
with the Dive Marshall or the coastguard if the Dive Marshall is on the
boat, regarding the departure time, number of people on board, destination
and estimated time of return. On longer journeys, the coxswain and the Dive Marshall should consider using two boats and travelling as a pair so that assistance may be given if required. |
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| 5.2 Hard boats | ||
| Because of the cost and ease, more and more dive trips are undertaken, chartering a hard boat. This has a number of advantages, including: | ||
| 1. Local knowledge 2. Ability to go further off shore 3. A larger more stable diving platform |
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| The
risks of diving from a hard boat are the same as when diving from a RHIB.
When chartering a boat, you should make sure that all of the equipment identified
above is carried. |
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| 5.3 The following risks exist when using boats at sea | ||
| 5.3.1 Engine failure | ||
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An engine failure at sea can rapidly become a serious situation, if not dealt with correctly. To reduce the likelihood of this occurring, the following steps should be taken.
2. Check that engines are running well, and that no problems have been reported. 3. Carry enough fuel for the journey. Should an engine failure occur, common sense will dictate the appropriate procedure. However, the following will need to be assessed:
2. Are there divers in the water, and are they becoming separated from the boat? 3. Is the boat in any danger by drifting? If so, anchor the boat. 4. Is there any nearby assistance? |
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| 5.3.2 Getting lost | ||
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Getting
lost at sea can occasionally happen. Fog can rapidly drop and obscure
all visual references. Navigating out of sight of land can also be disorientating.
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| 5.3.3 Overdue divers | ||
| In the event
of divers not surfacing after the pre-arranged time, they should be recalled.
This can either be by tugging on the SMB line, by deploying a weighted “thunderflash”,
or some other appropriate means. Divers failing to return after the recall
signal (accounting for any expected decompression obligations) should be
considered lost. |
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| 5.3.4 Lost Divers | ||
| In the event of a diver being considered lost, the coastguard or other local rescue agency should be notified immediately. If at last known location of the divers, and their dive plan should be given. The agency will then co-ordinate any rescue. | ||
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www.ouueg.org.uk |
