Deco gas choice for this dive?

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If you use 28% on the Lady Luck, you wouldn't really have that much to drain. The tanks will be fairly low after the dive anyway, so just finish bleeding them down low. If you top up from 300 to 500 psi or so, you might end up around 22-23%, which would still be fine for the Hydro. I wouldn't dive the Hydro on air, but that's just me.
^^ What he says.

You are using imperial so I did have to convert: 150' is 45 mt so 5.5 bar so the max FO2 to have 1.4 on the bottom is 25%.
So filling EAN28 and then topping off with air will give you - even starting with 100 bar (1500 PSI) - a good Nitrox (EAN25) for the second dive. Less leftover leaner nitrox for the second dive. Maybe you want to plan the second one on EAN25 and go for it.

Also EAN50 for deco is a standard gas and easy to fill (as many have indicated). Would stay on that mix because you would switch at a standard depth. If you have the training and the experience diving in benign condition to 45 is not a big deal, but be wary a bit of (too much) effort and or dark/cold situation will generate CO2 and multiply the nark effect.

And just to be sure, diving Nitrox will not decrease narcosis will increase density and NDL.

My 2 bar
 
hi kyle you will be subject to some narcosis diving those depths on air - so keep your dive plan simple and take one deco gas (50%)as someone mentioned earlier if it goes sour you can get on the deco gas sooner, im picking because you asking these questions this is newish territory fro you and your buddies ? so dont overburden yourselves with 100 and 50%
- use the first dive to measure your skills and protocols and see how you deal with the team work - the second dive you will notice the narcosis esp if theres current make sure your all comfortable with how the first dive went - have a debrief
if you are certified to do so Id do the deeper dive on a weak trimix esp if you are planning to penetrate
 
With the wreck in 175 feet and her mast at 120 feet, I can’t understand either plan. If the first dive is a check out dive why not do it on nitrox with no stops and start the next dive with a clean sheet and plan it to 175 feet
 
Try and stick to standard gas mixes, especially for deco gases: 50% and 100%.

Using custom gas (best) mixes for bottom and deco gases is very old school. Very few are doing that for deco gases now.

Shaving a couple minutes off a deco schedule isn’t worth the benefits of standardized mixes and permanently marked tanks.
 
For dive 1, I would use 32% as others have stated above, the 30 min BT will *probably* be within NDL and any deco should clear on the way up if you have spent any time on shallower parts. I would then carry a "deco" bottle of 32%, which would allow the training benefits of switching bottles etc but without the risk of actual deco on a dive that doesn't need it. You could switch back to backgas once the drills are completed, leaving the 32% deco gas basically unused if that made financial sense. Going into deco when it isn't necessary makes my risk-tolerance itch....

For the second dive, top up your 32 leftovers with air and plan the dive based on what's left, should save a few bucks since its an air fill at that stage and its nowhere near as frustrating as listening to your unused helium draining in a fill room.

Your certification of "one deco gas, limited deco" is a common one throughout the agencies. The idea is for limited exposures and less complication before moving on to multi deco gases, so the fallback is backgas deco if you lose a gas. In the dives I have run/planned in that category, 50% almost always comes out tops due to logistics, standardisation and not much deco penalty. Thats not to say that a team can't use some gas that makes sense but there are few reasonable arguments for something like 65%.

My thought would be to stick with the gases everyone is most likely to be using throughout your tech career and suck up the few minutes of extra deco unless those few minutes are a major issue (serious cold water etc etc).

Also, keep an eye on those gas densities, you REALLY don't want to be doing ANY serious effort on the bottom at 6.5g/L .That can bite you hard and fast especially if its cold and/or dark. I had a benign dive go a little sideways with some current recently and boy did I wish I had some helium in the mix. To the extent where I (personal choice) am not diving nitrox deeper than 130' again.
 
For dive 1, I would use 32% as others have stated above, the 30 min BT will *probably* be within NDL and any deco should clear on the way up if you have spent any time on shallower parts. I would then carry a "deco" bottle of 32%, which would allow the training benefits of switching bottles etc but without the risk of actual deco on a dive that doesn't need it. You could switch back to backgas once the drills are completed, leaving the 32% deco gas basically unused if that made financial sense. Going into deco when it isn't necessary makes my risk-tolerance itch....

For the second dive, top up your 32 leftovers with air and plan the dive based on what's left, should save a few bucks since its an air fill at that stage and its nowhere near as frustrating as listening to your unused helium draining in a fill room.

Your certification of "one deco gas, limited deco" is a common one throughout the agencies. The idea is for limited exposures and less complication before moving on to multi deco gases, so the fallback is backgas deco if you lose a gas. In the dives I have run/planned in that category, 50% almost always comes out tops due to logistics, standardisation and not much deco penalty. Thats not to say that a team can't use some gas that makes sense but there are few reasonable arguments for something like 65%.

My thought would be to stick with the gases everyone is most likely to be using throughout your tech career and suck up the few minutes of extra deco unless those few minutes are a major issue (serious cold water etc etc).

Also, keep an eye on those gas densities, you REALLY don't want to be doing ANY serious effort on the bottom at 6.5g/L .That can bite you hard and fast especially if its cold and/or dark. I had a benign dive go a little sideways with some current recently and boy did I wish I had some helium in the mix. To the extent where I (personal choice) am not diving nitrox deeper than 130' again.

Thanks for your thoughts
 
Don't use 32% on the Lady Luck unless you are going to strictly limit yourself to the deck. A couple of weeks ago I hit 136' in the sand at the props. 32% would spike your PO2 to just over 1.6. If you want to see all of the wreck, 28% is a good choice. I think @RainPilot was making suggestions based on your dive plan. I definitely agree about watching your gas densities. For me, anything past 130' gets helium.
 
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