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Gas Management

Gas Management. We will cover. Disciplined approach Gas required = time x breathing rate x ambient pressure Personal gas use Surface gas consumption Gas rules Emergency. Personal Gas Consumption. Surface gas consumption RMV Assess RMV - dive RMV at depth Individual differences

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Gas Management

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  1. Gas Management

  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. Personal Gas Consumption • Surface gas consumption • RMV • Assess RMV - dive • RMV at depth • Individual differences • Work rate • Importance

  4. 27 bar drop x 12 = 162 litres Gas Consumption = 2 bar 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

  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. 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. 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. Rules • Gas mix same - redundancy • Gas consumption – highest RMV • Available gas – least litres • Carry required gas

  9. Rules – example • Gas Management: • 3 Phases • Descent & Bottom Phase • Ascent & Deep Stops • Decompression Stops

  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. 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. 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. 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. 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. 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. 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. Emergency Situations • Two types of emergencies: • Missed shot-line/ascent in open water • Gas OK • Deploy RED surface marker buoy • Missed shot-line/ascent in open water • Gas needed for decompression • Deploy YELLOW surface marker buoy

  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. Questions?

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