1. Copyright 2012 CFT GAS/1 Gas Management

2. Copyright 2012 CFT GAS/2 We will cover  Disciplined approach  Gas required = time x breathing rate x ambient pressure  Personal gas use  Surface gas consumption  Gas rules  Emergency

3. Copyright 2012 CFT GAS/3 Personal Gas Consumption  Surface gas consumption  RMV  Assess RMV - dive  RMV at depth  Individual differences  Work rate  Importance

4. Copyright 2012 CFT GAS/4 Personal Gas Consumption Example Fin at 10m for 10 minutes, 12L cylinder Start 202 bar, End 175 bar Divide by the time = 162/10 Respiratory Minute Volume = 16.2 litres per minute 27 bar drop x 12 2 bar = 162 litres Gas Consumption =

5. Copyright 2012 CFT GAS/5 Personal Gas Consumption  Gas consumption = Respiratory Minute Volume (RMV) x pressure of the planned depth. For example, Dive to 30m: 4 bar pressure x RMV 16.2 litre = 64.8 litres per minute.  RMV – Individual, Exercise, Stress  6 l/min – 60 l/min, Avg. ~ 20 l/min

6. Copyright 2012 CFT GAS/6 Personal Gas Consumption  Example - Calculating gas duration  Dive 30m, RMV at depth 64.8 l/min  12 litre cylinder, 232 bar  232 Bar x 12 litres = 2784 litres  2784 litres/ 64.8 litres per minute = 43 minutes

7. Copyright 2012 CFT GAS/7 Rules  On dives: deeper than 40m involving decompression overhead environment  Rule of Thirds – bottom gas  Enough to decompress on back gas  Amount x 1.5 – decompression gas

8. Copyright 2012 CFT GAS/8 Rules  Gas mix same - redundancy  Gas consumption – highest RMV  Available gas – least litres  Carry required gas

9. Copyright 2012 CFT GAS/9 Rules – example  Gas Management:  3 Phases Descent & Bottom Phase Ascent & Deep Stops Decompression Stops

10. Copyright 2012 CFT GAS/10 Rules – example Dive 30m, 40 min, EAN 35 Deco: 4.5m, 8 min, EAN 50 RMV: 16.2 l/min Leave Bottom: 36 min Deep Stops: 2 stops, Total 4 min Decompression Stop: 8 min Ascent: 3 min

11. Copyright 2012 CFT GAS/11 Rules – example Bottom Mix: Descent & Bottom Phase: 30m = 4 Bar RMV at depth = 16.2 x 4 = 64.8 l/min Gas Required = RMV at depth x Time = 64.8 x 36 = 2,333 litres

12. Copyright 2012 CFT GAS/12 Rules – example Bottom Mix: Ascent & Deep Stops: RMV at Depth = RMV x Pressure Avg. Pressure = (4 Bar + 1 Bar)/2 = 2.5 Bar RMV at Depth = 16.2 x 2.5 = 40.5 l/min Time = Actual Ascent + Deep Stops = 3 + 4 = 7 minutes

13. Copyright 2012 CFT GAS/13 Rules – example Bottom Mix: Ascent & Deep Stops: Gas Required = RMV at depth x Time = 40.5 x 7 = 284 litres Total Bottom Mix = 2333 + 284 = 2,617 litres of EAN 35

14. Copyright 2012 CFT GAS/14 Rules – example Rule of Thirds Two thirds = 2617 litres Total gas required = 3926 litres Require: 2 x 12 litre cylinders @ 164 bar Fill cylinders to rated pressure

15. Copyright 2012 CFT GAS/15 Rules – example Decompression stop at 4.5m RMV on stop = 16.2 x 1.45 = 23.5 l/min Stop 8 min = 23.5 x 8 = 188 litres Gas rule 1.5x usage = 188 x 1.5 = 282 litres Require: 3 litre cylinder EAN 50 @ 94 Bar Fill cylinder to rated pressure

16. Copyright 2012 CFT GAS/16 Rules – example Loss of Decompression Gas Deco Stop, EAN 35: 4.5m, 11 min RMV = 16.2 x 1.45 = 23.5 l/min Stop 11 min Extra EAN 35 required = 23.5 x 11 = 259 litres Met by reserve of 1308 litres

17. Copyright 2012 CFT GAS/17 Emergency Situations  Two types of emergencies: 1. Missed shot-line/ascent in open water  Gas OK  Deploy RED surface marker buoy 2. Missed shot-line/ascent in open water  Gas needed for decompression  Deploy YELLOW surface marker buoy

18. Copyright 2012 CFT GAS/18 We have covered  Disciplined approach  Gas required = time x breathing rate x ambient pressure  Personal gas use  Surface gas consumption  Gas rules  Emergency

19. Copyright 2012 CFT GAS/19 Questions?