Lite Nitrox at 145

[Eastwest]

The Moody is a cool wreck dive at 145 here in Los Angeles and wonder about getting with the times rather than 1995 air only dive . I hope to be in good enough shape with some pratice this year or two . What advice on a mix of air would you suggest with a 30 minute bottom time .

 

[Nick_Radov]

Trimix 21/35 would be a good choice for bottom gas based on work of breathing, oxygen exposure, and equivalent narcotic depth. Add nitrox 50 for deco. Have you been trained for those dives?

 

[Tracy]

I would use 25/25 or 21/35 depending on the group I am diving it with.

 

[clownfishsydney]

He asked for Nitrox mix, not Trimix. 145 feet is 45 metres. For wrecks of that depth in Sydney, I always use 26%.

 

[ChuckP]

Personally, I'd do air with a 50 and 100 - easy 60 minute dive - 50 only leaves you about 15 minutes extra and I'd have to pee.

25% blend only gets you 4 minutes and not worth the effort IMO and I'm fine at that depth and conditions on air.

For the Trimix smoothies - the bottom is 140-145 - you certainly don't have your belly in the sand the whole dive, it's big wreck, you might have a 125' deep bottom time average. Yes it's cold, maybe a current but that's all known ahead of time and thought about, there's no rule about saying enough is enough, time to go.

That's an advanced advanced dive with that bottom time on whatever gas you choose, don't take deco lightly and get the training.

 

[Nick_Radov]

He asked for Nitrox mix, not Trimix. 145 feet is 45 metres. For wrecks of that depth in Sydney, I always use 26%.

He asked the wrong question. Nitrox is not a smart choice for a 145ft (44m) dive. I'm not going to waste time explaining the basics of gas selection again, this has already been discussed ad nauseum in multiple threads so anyone who cares can just search the archives. Or take an entry-level technical training course from a competent instructor.

 

[johndiver999]

If the op is so uniformed that he can not calculate an appropriate nitrox mix based on the depth and his po2 selection, then telling him to use helium is kinda silly.

I would use 27 % and try to stay off the bottom, but the proposed dive plan would rack up some significant deco, which may also be way outside the op’s skill set.

Kinda like “I don’t know how to drive stick shift; so what kind of driving sunglasses should I use”?

 

[Angelo Farina]

He asked for Nitrox mix, not Trimix. 145 feet is 45 metres. For wrecks of that depth in Sydney, I always use 26%.

I use air, no problem down to 50m. This is what I am certified for, since 1978. Let's call it Nitrox-21, it is just the perfect oxygen percentage between 45m and 50m.
Of course, some higher Nitrox can be used for speeding up the deco stops.
So my recipe would be:
- bottom gas: Nitrox 21%
- deco gas: Nitrox 50%
The benefits of going beyond 21% for bottom gas are negligible, whilst the additional risk of exceeding the MOD are not worth these minimal advantages.
Same for deco gas: the advantages of going beyond 50% are negligible, and the risks much higher.

 

[lowwall]

The Moody is a cool wreck dive at 145 here in Los Angeles and wonder about getting with the times rather than 1995 air only dive . I hope to be in good enough shape with some pratice this year or two . What advice on a mix of air would you suggest with a 30 minute bottom time .

@Nick_Radov is being his usual blunt to the point of rudeness self, but he does have a valid point about getting further training.

145' is beyond recreational limits for any US training agency. It's also deep enough that you can't increase the O2 percentage more than a few points without being concerned about the possibility of O2 toxicity. You should really understand Nitrox physiology before diving it. It's actually super simple. If you can think in meters/bar (1 bar is essentially atmospheric pressure at the surface and every 10m/33’ of depth adds another bar), the whole thing is laid out in a few paragraphs here: IFDI - Nitrox Diver e-learning.

But Nitrox is most helpful in the 60'-130' range. If you are regularly going beyond that, you should really be considering a trimix class. If you can afford the helium anyway. If not, then maybe reevaluate your personal max depths.

 

[rjack321]

The Moody is a cool wreck dive at 145 here in Los Angeles and wonder about getting with the times rather than 1995 air only dive . I hope to be in good enough shape with some pratice this year or two . What advice on a mix of air would you suggest with a 30 minute bottom time .

"Good enough shape" what *exactly* does this mean?

It takes basically zero fitness to go up and down a line with 20-30mins of deco time. For the record I would not do this dive at all without at least some helium.