I have been reading an interesting manual from IANTD and I could not get over how much this makes sense, so I thought I would share it with my readers!
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- Analyze all gases prior to diving;
- Ensure all gases are properly and visibly labeled prior to diving;
- Use 1.4 PPO2 on technical level exposures as a bottom and 1.6 as a maximum decompression mix PPO2
- After a period of acitvity at the surface (kitting up), allow for a short rest period in order to get breathing and heart rate back under control prior to entering water. Experienced divers may use visualization techniques or bodycardial breathing to achieve this. In short, wtop whatever you are doing and breathe deeply for a period of time;
- During the descent, stop at 20ft (6msw). Perform a leak and general equipment check. THis wait time of an additional minute or so further allows the body to acclimate to the new environment. Temperature and light acclimatization may take several minutes (up to 25 minutes for major light changes), however this brief stop will allow the cardio-vascular system to return to near normal rates.
- Make a slow descent without excess exercise. Either free fall or use hand over hand techniques with shot lines in tidal areas. Finning down the line will use a lot of energy and produce CO2 that in turn predisposes us to narcosis and a range of other problems.
- Having reached the bottom take another brief period to adjust equipment and attain the correct buoyancy. All these extra stabilizing minutes are simply an attempt to return the body to a near surface functioning state such that it operates to maximum efficiency.
- During the dive, whenever possible use “pull and glide” techniques rather then heavy finning (with suitable respect for the environment). Use of the arms reduce breathing stress.
- If at any point during the dive a stressful situation arises, STOP, take 3 deep breaths (focus on breathing out), Think and Act in that order. Try and prioritize the problems. The bottom line being if I have gas I can breathe. There is no urgency to start an ascent if at the end of the planned time something happens which slows egress providing bailout schedules are (and should be) carried.
- If the depth of the dive is known, carry a schedule for the dive time and the dive time plus 5 minutes. If the depth is uncertain carry a schedule for the depth and the time and the depth plus at least 10ft (3m) and the same time. Carry an additional schedule for the longest time and deepest depth assuming a decompression on bottom mix.
- Always plan for the deepest part of the dive even if this portion is only a bounce, i.e. if the wreck bottoms at 229fsw (70 msw), but most of the dive is at 223fsw (68 msw), plan for 229 fsw (70 msw). Maintain ascent rates of 33ft/minute (10 m/minute) or less, even from deep water.
- As with a no-stop dive where it is wise not to return directly to the surface (as this is a calculated pressure ceiling), it is also wise not to return directly to the first decompression stop. One or two minutes spent waiting 10fsw (3msw) below the first stop are beneficial when considering tissue over pressurization and will have no noticeable affect on the remaining decompression.
- Avoid unnecessary deplays in deep water on bottom mix, such as starting up a wall after planned bottom time and then taking time to stop and look.
- Do not reduce stop times arbitrarily. Do not make assumptions on stop time reduction if using a non planned gas without first computing for the effects. In a team plan this would mean carry a schedule for the worst gas scenario of the team (most deco).
- When reaching the first stop and if using a time device which works in whole minutes. Wait until the minute has incremented and then start the timing at that stop.
- If the stop involves a gas switch, start the stop timing after at least 3 - 4 breaths using the gas.
- Maintain stop accurracy to +/- 1fsw (.5 msw)
- After completing the final stop, ascend half way to the surface and stop for a further 2 - 5 minutes.
- While waiting for the boat to pick you up, stay on the highest available FO2
- Upon entry into the boat after a period of decompression, spend at least 5 minutes breathing your highest available FO2 on the surface.
- Hydrate with non-acidic drinks at least 12 hours before planned extended decompression dive. Hydrate again prior to the dive and immediately afterwards
- Avoid alcholic beverages, caffine and decongestants prior to diving.
- Do not smoke, especially immediately before and after a dive.
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These points are pretty much common sense things, but how many people skip past some, out of complancy??
