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| A. GAS Management HANDY SAFETY GUIDELINES 1) Limit bottom mix to ppo2 max @ 1.4. 2) Limit deco gas to PPo2 max @ 1.6. 3) Always analyze your own gas prior to diving. 4)No metal to metal connections on stage bottles, cuttable links after brass clips. 5) Return to deck of the boat with 1/3 bottom mix remaining as emergency reserve. 6) Verify by looking at tank what gas you are switching to during gas switches. 7) Use a guide line where needed. 8) Dive with a lift bag and up-line and know how to use it. 9) Do not stay on o2 when swimming to ladder from anchor line. 10) Do not dive with suicide clips. 11) Check that tank valves are on and isolation valve is open prior to donning tanks. 12) Properly label tanks and tank contents. 13) Do not dive with defective or malfunctioning equipment . 14) Know what your total cns dose is for any particular dive or combination of dives and deco's. B. Rule of thumb gas management Dear crew and diver, Remember back in the old days when " they " said come out of the water with 500 psi ? in your single tank. That amount of reserve is not adequate for technical diving (defined as planned staged decompression diving with or with out gas switches and duel tanks ) The cave diving rule of thirds doesn’t apply correctly ether . One-third in (turn around and start exiting) one third out, one third in reserve, the reserve third is for delays in exiting or to give to your partner in case of a failure in his gas supply. You need to always have enough gas to deal with the unforseen problems; getting tangled near the end of the dive or having your deco gas unavailable for some reason (the mind boggles at the many reasons this can happen) or to get you and your partner back to the up line or shot up a bag in case of a gas failure (then start your deco on back gas). or to go back down after your buddy or someone else if you see them drop off the line incapacitated for some reason. A good starting point on how much gas to save in reserve would be 10 or 15 minutes of bottom gas for both you and your dive partner combined at the deep part of your planned dive . Remember your deco gas plays no part in this calculation. You can figure this volume out by adding together your SAC rates then (Surface Air Comsumpton) multiplying by the depth /33 multiplyed by 10 or 15 minutes, depending on what volume tanks you wear is how many psi this adds up to. For example combined SAC rate of 1.2 X 5 ATA = 6.0. If the team uses 6 cfm at depth 6 x 15 = 90 cubic feet of gas or 6 x 10 = 60 . Take the volume of tank you use and divide it by the rated pressure at that volume. Example: divide tank volume into rated pressure to get your constant to determind your tank volume at any psi. divide 121 cu. ft. by 2640 psi = .0458 this figure is how many cu ft / psi these OMS 121 tanks hold divide 90 cu ft by the constant you have derived 90 /.0458 = 1965 1965 / 2 tanks = 982.5 psi in each tank at a minimum thirds in those tanks filled to spec would only be 879 psi |