Chapter 11- Technical Diving Technical Diving 253 Technical divers use highly redundant systems on extreme dives. Technical diving in caves also requires that equipment be streamlined for safety and protection of delicate cave formations. Many of the cylinders can be staged before the dive, but redundancy often requires the diver to wear as many as four large cylinders. A typical configuration might consist of two 3000 L (104 cubic foot) cylinders with a crossover manifold and two regulators which contain the bottom mix, and a pair of side tanks which contain the decompression gases nitrox and oxygen, each with their own regulators secured to the diver’s harness. Technical divers are looking forward to the continued development of closed circuit technology that will eliminate the need to carry so many cylinders. A fully redundant closed circuit rebreather, which recirculates exhaled breathing gas that has been “scrubbed” of carbon dioxide and had oxygen added could potentially offer a 12 hour gas supply (figure 11-5). This will certainly change the way many technical divers go about their avocation. There is a considerable history of rebreather research and development, especially in the military. Some units use pure oxygen only and are consequently limited to a depth of 8 m (25 ft). A semi-closed rebreather emits only a few small bubbles and consists of a cylinder that can use nitrox gas, breathing bags, absorbent canister, and regulator. Premixed gas flows constantly, usually providing about two hours dive duration. Improved thermal balance can be achieved by the heat that is generated from the scrubber canister. These units are relatively simple, without complicated electronics. Newer, fully automated electronic and computer-controlled units are much more sophisticated. Potential hazards of diving with a rebreather include hyperoxia (which can lead to oxygen toxicity), inhalation of caustic carbon dioxide absorbent material and gases, hypercapnea, hypoxia, DCI, failure of electronics, and contamination from previous users (if not properly disinfected). Additional important equipment for technical FIGURE 11-5. REBREATHER DIVERS
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