Gases for 50M dive

[Divetech99]

Andy, you bring up some very enlightening points. Really appreciate your inputs. Don't stop .

Question, what GF setting do you use for your tech dives?

On your typical 50m Tec dive, what do you use for your back gas and deco gas?

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[DevonDiver]

GF varies depending on the dive, especially depth range. I prefer VPM-B, at +3.

If using buhlmann ZHL16-B+GF, for a 50m dive my gradient factors would be 20/70.

i.e. 50m for 30 mins GF20/70 vs VPM-B +3
D____ GF____VPM
50____30_____30--------21%
30_____1______1
27_____1______1
24_____1______2
21_____2______2-------- 50%
18_____2______3
15_____4______3
12_____4______5
9______7______6
6______7______7------ 100%
3_____12_____10
RT___(74)____(73)

For a 50m dive, backgas is invariably air. Philippines diving is not so bad for narcosis, but cost of helium here is very bad for the wallet. I deco with 50% only down to 45m. Beyond that, I use 50% + 100%.

 

[PfcAJ]

18/45 with 50% as deco gas, adding 100% if the exposure is more than about 20-30mins.

 

[ajduplessis]

I dont do textbook stuff so a 20/25 or 20/20 on a 50m dive with 50&100 deco gasses running vpm +1.
18/45 IMO is a dive profile overkill and finacially crippling exercise for 50m depths.

 

[Centrals]

Unless it is wreck penetration otherwise 50m is always on AIR.
GF 20/80 with 50% and 100%.

 

[Kevrumbo]

Was 30/85; is now 40/70 per Simon Mitchell's initial recommendation per the NEDU Deep Stops Study.

On multi-week Expedition Trips: On the third consecutive day of two dives per day diving maximum fN2 bottom mixes like Air 45m or deeper with 50% and O2 Deco, I would decrease the surfacing GF Hi from 70 to 60 (that is extend the Oxygen Deco profile to further off gas slow tissues); after three or four consecutive days, take a day off from diving to recover from CNS O2 exposure & additionally off gas residual N2 from the slow tissues.

 

[Michael Guerrero]

If no pentration and assuming BT of ~30 min then air, 50% & 100%, GF 50/85.

 

[kensuf]

21/35 + 50% + O2 for dives more than 30 minutes.

 

[Tug]

21/35 + 50% + O2 for dives more than 30 minutes.

Same here (or at least it was when I was diving OC)

 

[Nasser]

Depending on dive and conditions either Air or 20/30 with 50% and 80%

GF 40/75