Chapter 10- Diving Techniques and Deeper Diving Diving Techniques and Deeper Diving 241 liter/200 bar cylinder. His/her air consumption rate is: 100 bar / 20 minutes = 5 bar/min We can now calculate the surface air consumption. If the diver consumed a given amount of air at 10 m (i.e., 2 ata) at the same breathing rate, how much air would that diver consume at the surface (1 ata) at the same breathing rate? The diver would consume half as much or 2.5 bar/minute. By determining your air consumption in bar (or “psi”) at a fixed depth using a given size cylinder, you can compute the estimated consumption at the surface at the other depths. Using the surface air consumption rate, simply multiply the surface air consumption rate by the absolute pressure at the planned depth. For example, at a depth of 24 meters, the absolute pressure is: 24 m + 1 atm = 3.4 ata 10 m/atm and your air consumption rate at depth is: 2.5 bar/min X 3.4 = 8.5 bar/min Assuming that 165 bar of air is available (35 bar is saved for reserve) and all the air is consumed at depth, the air supply would be satifactory for approximately 19 minutes. English (Imperial) Example A diver breathes 1500 psi in 20 minutes at a depth of 33 feet from a standard aluminum “80.” His/her air consumption rate is: 1500 psig / 20 minutes = 75 psi/min Since the air consumption was measured at 33 feet (2 ata), the diver’s surface air consumption rate would be half as great or 37.5 psi/min. If the diver dives to a depth of 90 feet, where the absolute pressure is: 90 ft + 1 atm = 3.73 ata 33 ft/atm his/her air consumption at depth will be: 37.5 psi/min X 3.73 = 140 psi/min Assuming that 2500 psi of air is available (500 psi is saved for reserve) and all the air is consumed at depth, the air supply would be satisfactory for approximately 18 minutes. Emergency Procedure Considerations Due to the increased risks in deep diving, a finetuned emergency procedure is necessary. After all, your life may depend on it. By doing your deep dives through organized courses and NAUI affiliated stores and resorts, you will be supported with highly trained professionals and a fine-tuned emergency procedure. Look for: • Trained professional staff—currently certified Divemasters and/or Instructors with current Dive Rescue, CPR, and diving first aid training. • Rescue equipment including O2 kit, first aid kit, backboard, and blanket. • Communication equipment which may include UHF radio, CB radio, or telephones to alert medical support, if necessary. • Information and an access plan for evacuation of a victim to the nearest hospital and/or chamber. • Transportation by boat and/or vehicle for evacuation. • Contact information for the Divers Alert Network (DAN) for advice in emergency evacuation and hyperbaric treatment. Remember, good accident management is no accident. It takes a serious amount of training, experience, and dedication to produce competent, efficient emergency procedures. Your piece of mind is worth a few extra dollars to dive with professionals. If you are diving on your own, you will have to prepare your own emergency plan using the guidelines above. You will have to decide to what detail you will provide for yourselves, and what kind of local assistance can be obtained. Any training that you can get in the areas of oxygen administration, first aid, and diver rescue will be beneficial.
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