Blue Hole 25th of January 2011. Depth 90 meter Last dive of Full Trimix Course.
Divers:
Jonas Samuelsson Instructor
Erik Brown - Student
Zdenek Jankovsky Assisting instructor
To read the full brief
Support Diver:
Zakaria El Sayed
Dahab Egypt. Eilat Israel, Koh Tao Thailand
Planning a dive using V-Planner (by Erik C. Baker) and Combined Decompression Model Dive Profile Analyzer CDM-18 (by Steve Burton)
The dive was a bounce dive to 90 meters with a bottom time of only 2 minutes. Preparation before a trimix dive requires discussons related to many areas. Here we talk briefly about planning a dive using decompression software with the added touch of Steve Burtons CDM-18.
Below are just some points that we discussed regarding our diveplan on this particular day. We are not saying that the below plan is safe and neither is the designers of the V-Planner and CDM-18. You should dive within the limits of your training and remember you use any information on this website at your own risk. The purpose of this little article is purely to illustrate some discussion points between team members prior to a mixed gas dive.
Divesite:
We started by looking at the divesite in it self. The Blue Hole in Dahab with an easy access and good visibily combined with a water temperature of 25 degrees and no current made this an ideal site for a 90 meter dive.
We were planning to descent following the contour of the Blue Hole to the entry of the Arch and have a little peak inside (our bottom time did not allow for a dive through the Arch and back). We were three divers going to 90 meters and we had one support diver meeting us at 21 meters during the ascent.
We all agree that the dive site was suitable for the dive.
V-Planner Configuration:
We then looked at the configurations of the V-Planner. We choose a SAC rate of 20 liters/minute both for the bottom gas/travel gas and the deco. We all had better SAC rates than this, but better to be conservative when it comes to gas planning. The descent rate was set at 15 meters/min (also a fairly slow descent rate, but once again a more conservative one). Our ascent rate was set for 9 meter per minute for the ongassing phase of the dive and 6 meters/minute for the off gassing phase (see plan below, off gassing starts at 59 meters and thats where we slowed down from 9 m/min to 6 m/min.). Our accepted ppO2 for theO2 decompression part of the dive was set at 1.4 ppOO2 for the mix with O2 up to 28%, 1.5 ppO2 up to 45% and 1.6 ppO2 up to 99%. We used conservatism "+2" in the V Planner Configurations.
Bottom gas, 12/60
Oxygen:
We wanted our bottom ppO2 to be well within 1.4ppO2 so we choose a mix with 12% O2 which gave us a pp02 of only 1.19. well within our set limits, all to avoid CNS Problems.
Helium:
We wanted to keep our END (Equivalent Narcosis Depth) low so we chosed a 60% HE mix which gave us an END of 30 meters. HPNS was not an issue being shallower than 100 meter so high HE mix in the bottom mix was not a consideration.
Nitrogen:
So we ended up with a low 28% Nitrogen mix in our bottomgas which resulted in a low END as mentioned above. This amount also relates to ICD considerations during our gas switch at 21 meters. We dont want to change to a deco gas with a higher Nitrogen level than our bottom gas due to risk of ICD (Isobaric Counter Diffusion - There is still a lot of discussion about prevention of DCS type III caused by ICD, generally accepted rule for a gas switch is that for every 5% decrease of helium can be nitrogen increased by 1%, recent discussion leads to more complex rules for extreme dives but to keep it super simple: basic rule is to avoid any jumps in ppN2 (links to more detailed discussions are available on www.blue-immersion.org)). Our gas planning discussion resulted in the below Deco gas.
Deco gas 1, 50/20
Oxygen:
We decided for 50% mix in our first deco gas. 50% is a gas with a great efficiency ratio of 1:1.32 (compared to Air - 1:1). Its of course lower than 80% O2 (1:1.37) and 100% O2 (1.1.42) but the advantage is that you can use this gas within ppO2 of 1.6 already at 21 meters making it a very flexible gas.
Helium
To avoid ICD (Isobaric Counter Diffiusion) we mixed out first deco gas with 20% HE to offset the effects of ICD. Remember that we had 28% Nitrogen in our bottom mix. So to avoid ICD problems we want our total amount of Nitrogen (Inert Gas) to be lower after the switch. By having 50/20 mix we only increased our Nitrogen mix with 2% which we decided was within acceptable limits in our planning for ICD avoidance. Our goal is to always avoid any jumps in ppN2. (The planned gas was approved by check in Steve Burtons CDM-18***).
Nitrogen:
Set low to avoid ICD.
Deco gas 2, 100%
Oxygen:
We switched to 100% O2 at 6 meters for an efficient offgassing during the last, and most important part, of our decompression. We also added 3 minutes of breathing 100% O2 during our ascent from 3 meters to the surface. Our ascent rate for the last 3 meters was a very conservative 1 meter/minute. Now we looked at our OTUs and CNS which both were well below accepted limits for oxygen exposure. We had one issue regarding Air Breaks. Our total time breathing 100% O2 was 16 minutes (6 meter and 3 meter stops plus 3 minutes for the added ascent from 3 meter to the surface and 3 minute safety stop on the surface). We decided to take an Air break using the 50/20 mix with less Helium than the bottom mix after 12 minutes on pure oxygen. Due to the low levels of O2 (12%) in the bottom mix and the ICD risk we decided that breathing 70% Helium during the Air break would have increased our risk of ICD due to Heliums fast on gassing, moreover our bottom mix is hypoxic and at 3 meters would be ppO2 below 0,18. We always plan air breaks for exposure of 100% O2 for more than 15 minutes. So the total time of the dive was actually 58 minutes (total run time: 49 minutes plus 3 minutes added for the ascent from 3 meters to the surface, 3 minute air break (using 50/20 mix during last deco stop at 3 meters and 3 minutes safety stop breathing pure oxygen on the surface).
Brief summary of a planning a trimix dive in bluehole dahab. tec rec trimix course 90 meters |
Travel gas:
We decided to use our 50/20 mix to a depth of 10 meters where we safetly could breath from our bottom mix of 12/60. Using Travelgas did not change the runtime of the dive and did not have any measurable effect on our gases (approx 20 liters less of 50/20 and approx 20 liter more of our 12/60 mix a 10 meter descent using 15 meters/minute and breathing 20 liters per minute plus minus a few liters)
Bottom time:
We set, as mentioned earlier, our descent rate at 15 meters/minute so to our descent to 90 meters took us approx 6 minutes. So we decided to only stay for 2 minutes at 90 meters due to gas requirements.
Gas requirements for this dive were:
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
If we decided to stay a few minutes longer we would no longer have the required reserve to conduct the dive safely. We discussed bringing larger tanks than our 11 liters twins but decided for a shorter bottom time instead.
Lost gas:
We were three divers carried our tanks during the complete dive so we made a calculated assumption that the likelyhood of all three of us loosing both our 50/20 and 100 mix was very slim but anyway we decided to use support diver for this dive whom we met on our return at 21 meters and he was carrying one tank of each deco gas we were using on the dive.
No failures - normal dive - OK
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
Lost or missing deco gas: 50/20
4164.6 ltr Trimix 12/60
19.9 ltr Triox 50/20
474.0 ltr Oxygen
4658.5 ltr TOTAL
Lost or missing deco gas: 100
2786.2 ltr Trimix 12/60
1155.6 ltr Triox 50/20
3941.8 ltr TOTAL
Lost or missing deco gas: Both
5767.7 ltr Trimix 12/60
19.9 ltr Triox 50/20
5787.7 ltr TOTAL
In Dahab you are required to have a support diver (s) for any dives deeper than 100 meters. Our dive depth was 90 meters. We did not need a support diver to assist us with tanks during our decos either. We only had two deco tanks. But its good practice for deeper dives and a support diver its always a great backup if everything else would fail. Someone with extra gas and a fresh mind couldnt not hurt was our reasoning.
Here is the full plan we used that day. The plan was checked using Steve Burtons excellent software The CDM-18 which I recommend to every technical diver to use after planning your dive using a deco software.
CDM-18 find if there is any problems with the dive plan in regards to ICD and DCS. There is a link further down to Steve's website if you are interested in buying your own version.
V-Planner 3.89 by Ross Hemingway,
VPM code by Erik C. Baker.
Decompression model: VPM - B
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0m
Conservatism = + 2
Dec to 10m (0) Triox 50/20 15m/min descent.
Dec to 65m (4) Trimix 12/60 15m/min descent.
Dec to 90m (6) Trimix 12/60 15m/min descent.
Level 90m 2:00 (8) Trimix 12/60 1.19 ppO2, 25m ead, 30m end
Asc to 59m (11) Trimix 12/60 -9m/min ascent.
Asc to 48m (13) Trimix 12/60 -6m/min ascent.
Stop at 48m 0:43 (14) Trimix 12/60 0.69 ppO2, 11m ead, 13m end
Stop at 39m 1:00 (16) Trimix 12/60 0.58 ppO2, 7m ead, 10m end
Stop at 36m 1:00 (17) Trimix 12/60 0.55 ppO2, 6m ead, 8m end
Stop at 33m 1:00 (18) Trimix 12/60 0.51 ppO2, 5m ead, 7m end
Stop at 30m 1:00 (19) Trimix 12/60 0.48 ppO2, 4m ead, 6m end
Stop at 27m 2:00 (21) Trimix 12/60 0.44 ppO2, 3m ead, 5m end
Stop at 24m 2:00 (23) Trimix 12/60 0.41 ppO2, 2m ead, 4m end
Stop at 21m 2:00 (25) Triox 50/20 1.54 ppO2, 2m ead, 15m end
Stop at 18m 2:00 (27) Triox 50/20 1.39 ppO2, 1m ead, 12m end
Stop at 15m 2:00 (29) Triox 50/20 1.24 ppO2, 0m ead, 10m end
Stop at 12m 3:00 (32) Triox 50/20 1.10 ppO2, 0m ead, 8m end
Stop at 9m 4:00 (36) Triox 50/20 0.95 ppO2, 0m ead, 5m end
Stop at 6m 5:00 (41) Oxygen 1.60 ppO2, 0m ead
Stop at 3m 8:00 (49) Oxygen 1.30 ppO2, 0m ead
Surface (49) Oxygen -6m/min ascent.
Off gassing starts at 59m
OTU's this dive: 50
CNS Total: 24.1%
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
Now when we agreed to the plan and checked and double checked that we were within ppO2 limits, that we had no or limited risk of DSC and ICD, that we had enough gas for the complete dive including lost gas scenarios. Our END of only 30 meters made sure we would not suffer from any considerate narcosis. The plan was signed and sealed.
The dive was conducted with the plan on a wrist slate as a primary and as backup we all had the plan written together with emergency scenarios in our wetnotes. As backup to the backup we carried mixed gas
The dive was conducted perfectly according to the plan and its was an amazing dive!
Dive safe and please share with us any comments that could improve the above diveplan. We would like to thank Steve Burton for tips and hints regarding ICD and Bruce Kenofe who provided us with ANDIs deco gas efficiency chart.
Jonas Samuelsson
Technical Diving Instructor Trainer
Teamblueimmersion@gmail.com
www.blue-immersion.org
Dahab Egypt, Eilat Israel, Koh Tao Thailand
Sources:
Steve Burton www.scubaengineer.com
ANDI Oxygen Efficiency Ratio
Written by:Jonas Samuelsson with team Members Zdenek Jankovsky and Erik Brown,
Team Blue Immersion, www.blue-immersion.org
Divers:
Jonas Samuelsson Instructor
Erik Brown - Student
Zdenek Jankovsky Assisting instructor
To read the full brief
Support Diver:
Zakaria El Sayed
Dahab Egypt. Eilat Israel, Koh Tao Thailand
Planning a dive using V-Planner (by Erik C. Baker) and Combined Decompression Model Dive Profile Analyzer CDM-18 (by Steve Burton)
The dive was a bounce dive to 90 meters with a bottom time of only 2 minutes. Preparation before a trimix dive requires discussons related to many areas. Here we talk briefly about planning a dive using decompression software with the added touch of Steve Burtons CDM-18.
Below are just some points that we discussed regarding our diveplan on this particular day. We are not saying that the below plan is safe and neither is the designers of the V-Planner and CDM-18. You should dive within the limits of your training and remember you use any information on this website at your own risk. The purpose of this little article is purely to illustrate some discussion points between team members prior to a mixed gas dive.
Divesite:
We started by looking at the divesite in it self. The Blue Hole in Dahab with an easy access and good visibily combined with a water temperature of 25 degrees and no current made this an ideal site for a 90 meter dive.
We were planning to descent following the contour of the Blue Hole to the entry of the Arch and have a little peak inside (our bottom time did not allow for a dive through the Arch and back). We were three divers going to 90 meters and we had one support diver meeting us at 21 meters during the ascent.
We all agree that the dive site was suitable for the dive.
V-Planner Configuration:
We then looked at the configurations of the V-Planner. We choose a SAC rate of 20 liters/minute both for the bottom gas/travel gas and the deco. We all had better SAC rates than this, but better to be conservative when it comes to gas planning. The descent rate was set at 15 meters/min (also a fairly slow descent rate, but once again a more conservative one). Our ascent rate was set for 9 meter per minute for the ongassing phase of the dive and 6 meters/minute for the off gassing phase (see plan below, off gassing starts at 59 meters and thats where we slowed down from 9 m/min to 6 m/min.). Our accepted ppO2 for theO2 decompression part of the dive was set at 1.4 ppOO2 for the mix with O2 up to 28%, 1.5 ppO2 up to 45% and 1.6 ppO2 up to 99%. We used conservatism "+2" in the V Planner Configurations.
Bottom gas, 12/60
Oxygen:
We wanted our bottom ppO2 to be well within 1.4ppO2 so we choose a mix with 12% O2 which gave us a pp02 of only 1.19. well within our set limits, all to avoid CNS Problems.
Helium:
We wanted to keep our END (Equivalent Narcosis Depth) low so we chosed a 60% HE mix which gave us an END of 30 meters. HPNS was not an issue being shallower than 100 meter so high HE mix in the bottom mix was not a consideration.
Nitrogen:
So we ended up with a low 28% Nitrogen mix in our bottomgas which resulted in a low END as mentioned above. This amount also relates to ICD considerations during our gas switch at 21 meters. We dont want to change to a deco gas with a higher Nitrogen level than our bottom gas due to risk of ICD (Isobaric Counter Diffusion - There is still a lot of discussion about prevention of DCS type III caused by ICD, generally accepted rule for a gas switch is that for every 5% decrease of helium can be nitrogen increased by 1%, recent discussion leads to more complex rules for extreme dives but to keep it super simple: basic rule is to avoid any jumps in ppN2 (links to more detailed discussions are available on www.blue-immersion.org)). Our gas planning discussion resulted in the below Deco gas.
Deco gas 1, 50/20
Oxygen:
We decided for 50% mix in our first deco gas. 50% is a gas with a great efficiency ratio of 1:1.32 (compared to Air - 1:1). Its of course lower than 80% O2 (1:1.37) and 100% O2 (1.1.42) but the advantage is that you can use this gas within ppO2 of 1.6 already at 21 meters making it a very flexible gas.
Helium
To avoid ICD (Isobaric Counter Diffiusion) we mixed out first deco gas with 20% HE to offset the effects of ICD. Remember that we had 28% Nitrogen in our bottom mix. So to avoid ICD problems we want our total amount of Nitrogen (Inert Gas) to be lower after the switch. By having 50/20 mix we only increased our Nitrogen mix with 2% which we decided was within acceptable limits in our planning for ICD avoidance. Our goal is to always avoid any jumps in ppN2. (The planned gas was approved by check in Steve Burtons CDM-18***).
Nitrogen:
Set low to avoid ICD.
Deco gas 2, 100%
Oxygen:
We switched to 100% O2 at 6 meters for an efficient offgassing during the last, and most important part, of our decompression. We also added 3 minutes of breathing 100% O2 during our ascent from 3 meters to the surface. Our ascent rate for the last 3 meters was a very conservative 1 meter/minute. Now we looked at our OTUs and CNS which both were well below accepted limits for oxygen exposure. We had one issue regarding Air Breaks. Our total time breathing 100% O2 was 16 minutes (6 meter and 3 meter stops plus 3 minutes for the added ascent from 3 meter to the surface and 3 minute safety stop on the surface). We decided to take an Air break using the 50/20 mix with less Helium than the bottom mix after 12 minutes on pure oxygen. Due to the low levels of O2 (12%) in the bottom mix and the ICD risk we decided that breathing 70% Helium during the Air break would have increased our risk of ICD due to Heliums fast on gassing, moreover our bottom mix is hypoxic and at 3 meters would be ppO2 below 0,18. We always plan air breaks for exposure of 100% O2 for more than 15 minutes. So the total time of the dive was actually 58 minutes (total run time: 49 minutes plus 3 minutes added for the ascent from 3 meters to the surface, 3 minute air break (using 50/20 mix during last deco stop at 3 meters and 3 minutes safety stop breathing pure oxygen on the surface).
Brief summary of a planning a trimix dive in bluehole dahab. tec rec trimix course 90 meters |
Travel gas:
We decided to use our 50/20 mix to a depth of 10 meters where we safetly could breath from our bottom mix of 12/60. Using Travelgas did not change the runtime of the dive and did not have any measurable effect on our gases (approx 20 liters less of 50/20 and approx 20 liter more of our 12/60 mix a 10 meter descent using 15 meters/minute and breathing 20 liters per minute plus minus a few liters)
Bottom time:
We set, as mentioned earlier, our descent rate at 15 meters/minute so to our descent to 90 meters took us approx 6 minutes. So we decided to only stay for 2 minutes at 90 meters due to gas requirements.
Gas requirements for this dive were:
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
If we decided to stay a few minutes longer we would no longer have the required reserve to conduct the dive safely. We discussed bringing larger tanks than our 11 liters twins but decided for a shorter bottom time instead.
Lost gas:
We were three divers carried our tanks during the complete dive so we made a calculated assumption that the likelyhood of all three of us loosing both our 50/20 and 100 mix was very slim but anyway we decided to use support diver for this dive whom we met on our return at 21 meters and he was carrying one tank of each deco gas we were using on the dive.
No failures - normal dive - OK
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
Lost or missing deco gas: 50/20
4164.6 ltr Trimix 12/60
19.9 ltr Triox 50/20
474.0 ltr Oxygen
4658.5 ltr TOTAL
Lost or missing deco gas: 100
2786.2 ltr Trimix 12/60
1155.6 ltr Triox 50/20
3941.8 ltr TOTAL
Lost or missing deco gas: Both
5767.7 ltr Trimix 12/60
19.9 ltr Triox 50/20
5787.7 ltr TOTAL
In Dahab you are required to have a support diver (s) for any dives deeper than 100 meters. Our dive depth was 90 meters. We did not need a support diver to assist us with tanks during our decos either. We only had two deco tanks. But its good practice for deeper dives and a support diver its always a great backup if everything else would fail. Someone with extra gas and a fresh mind couldnt not hurt was our reasoning.
Here is the full plan we used that day. The plan was checked using Steve Burtons excellent software The CDM-18 which I recommend to every technical diver to use after planning your dive using a deco software.
CDM-18 find if there is any problems with the dive plan in regards to ICD and DCS. There is a link further down to Steve's website if you are interested in buying your own version.
V-Planner 3.89 by Ross Hemingway,
VPM code by Erik C. Baker.
Decompression model: VPM - B
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0m
Conservatism = + 2
Dec to 10m (0) Triox 50/20 15m/min descent.
Dec to 65m (4) Trimix 12/60 15m/min descent.
Dec to 90m (6) Trimix 12/60 15m/min descent.
Level 90m 2:00 (8) Trimix 12/60 1.19 ppO2, 25m ead, 30m end
Asc to 59m (11) Trimix 12/60 -9m/min ascent.
Asc to 48m (13) Trimix 12/60 -6m/min ascent.
Stop at 48m 0:43 (14) Trimix 12/60 0.69 ppO2, 11m ead, 13m end
Stop at 39m 1:00 (16) Trimix 12/60 0.58 ppO2, 7m ead, 10m end
Stop at 36m 1:00 (17) Trimix 12/60 0.55 ppO2, 6m ead, 8m end
Stop at 33m 1:00 (18) Trimix 12/60 0.51 ppO2, 5m ead, 7m end
Stop at 30m 1:00 (19) Trimix 12/60 0.48 ppO2, 4m ead, 6m end
Stop at 27m 2:00 (21) Trimix 12/60 0.44 ppO2, 3m ead, 5m end
Stop at 24m 2:00 (23) Trimix 12/60 0.41 ppO2, 2m ead, 4m end
Stop at 21m 2:00 (25) Triox 50/20 1.54 ppO2, 2m ead, 15m end
Stop at 18m 2:00 (27) Triox 50/20 1.39 ppO2, 1m ead, 12m end
Stop at 15m 2:00 (29) Triox 50/20 1.24 ppO2, 0m ead, 10m end
Stop at 12m 3:00 (32) Triox 50/20 1.10 ppO2, 0m ead, 8m end
Stop at 9m 4:00 (36) Triox 50/20 0.95 ppO2, 0m ead, 5m end
Stop at 6m 5:00 (41) Oxygen 1.60 ppO2, 0m ead
Stop at 3m 8:00 (49) Oxygen 1.30 ppO2, 0m ead
Surface (49) Oxygen -6m/min ascent.
Off gassing starts at 59m
OTU's this dive: 50
CNS Total: 24.1%
2712.6 ltr Trimix 12/60
629.7 ltr Triox 50/20
364.2 ltr Oxygen
3706.5 ltr TOTAL
Now when we agreed to the plan and checked and double checked that we were within ppO2 limits, that we had no or limited risk of DSC and ICD, that we had enough gas for the complete dive including lost gas scenarios. Our END of only 30 meters made sure we would not suffer from any considerate narcosis. The plan was signed and sealed.
The dive was conducted with the plan on a wrist slate as a primary and as backup we all had the plan written together with emergency scenarios in our wetnotes. As backup to the backup we carried mixed gas
The dive was conducted perfectly according to the plan and its was an amazing dive!
Dive safe and please share with us any comments that could improve the above diveplan. We would like to thank Steve Burton for tips and hints regarding ICD and Bruce Kenofe who provided us with ANDIs deco gas efficiency chart.
Jonas Samuelsson
Technical Diving Instructor Trainer
Teamblueimmersion@gmail.com
www.blue-immersion.org
Dahab Egypt, Eilat Israel, Koh Tao Thailand
Sources:
Steve Burton www.scubaengineer.com
ANDI Oxygen Efficiency Ratio
Written by:Jonas Samuelsson with team Members Zdenek Jankovsky and Erik Brown,
Team Blue Immersion, www.blue-immersion.org
