Is nitrox worth it for deeper rec dives?

[BRT]

I for one am quite happy that Marie13 brought things up as the ensuing discussion taught me a lot following my study of the PADI manual and the course that I'll take in Feb. Hopefully wet in March if plans don't go awry.

From various posters I'm beginning to grok how different O2 percentages can be tailored to fit a particular plan. That is cool (if juggling a lot of variables). Next trip won't see a lot of deep dives (most 1st-dive-of-the-day to 60 - 80'), but there are 2 sites that get down to about 100 - 115'. I've been studying the tables (EAN32/36) with these in mind. (I don't know what flexibility the DC have on mix, however), but it's clear that I'll be either requesting a lower O2 mix or diving regular air at those sites.

A fellow I met last winter is going to sell me his backup computer (the one he lent me last year). He's off to Cozumel next week so I guess I'll get it on his return - just in time for my course.

Why wouldn't you just use 32% at 100-115'?

 

[Manatee Diver]

I can't say that I've run into it or read about it being offered at any of the shops that I've looked into diving with. Most shops either say "we have banked 3x % Nitrox" or "your tank must be O2 clean."

I know a number of shops that do partial pressure from banked nitrox.

Other than high traffic dive sites that are filling off a banked Nitrox tank...I have yet to see a CONUS reference to not requiring an O2 clean tank to get a Nitrox fill.

Even the high traffic places can run out of banked nitrox. I remember a recent dive in Key Largo where the operator ran out of banked EAN32, and couldn't do a nitrox fill for a guy whose tank wasn't oxygen service clean. That I why I maintain my steel tanks, the tanks that I almost exclusively use with nitrox, oxygen cleaned even though I almost always get banked mixes. *knocks on wood* To date I've never had to pay for an actual cleaning.

 

[Alan Browne]

Why wouldn't you just use 32% at 100-115'?

Pushing into the contingency band? 100+ is already safety stop (which I'd do anyway), 110 is 1.39 PPO2, 115 is about 1.43 (PADI 32% table).

 

[guruboy]

Doing continuous blending requires a running compressor for each fill. Banking does not.

 

[Jared0425]

Didnt read through the whole thread so if this was already mentioned so be it.

Diving Nitrox in the Great Lakes is almost a waste of time unless using it as a deco gas. The temperature below 70ft drives most people up long before they get close to their NDL or even stray into deco. Also with the extra heavy gear we use (dry suits, larger tanks, more backups) we use gas a little bit more as we need more effort to push our way through the water.

However one can have heat, great cold tolerance, and a scooter to extend the intended bottom time. However unheated and no thermocline I'm ready to go at 20 minutes. The people that I have dove with in the past that used nitrox as their primary back gas on dives between 80-120ish have thumbed it a ways before their NDL was up.

It gets worse when you add helium to the mix and your suit is leaking and the thermocline is only a 15° difference.

 

[Gareth J]

Jared0425, what's the temperature in the Great Lakes?

One of the issues of the discussion was the cumulative effect of multiple days of diving.
I know diving Scapa (Orkney Isles, Scotland). That Nitrox is better for you over a weeks diving.
I think the lowest I dived properly in was about 4Centigrade, for about 70 minutes a time, two dives a day over four days (Iceland).

 

[Storker]

I think the lowest I dived properly in was about 4Centigrade, for about 70 minutes a time, two dives a day over four days (Iceland).

That's pretty impressive. My coldest dive was 3C surface, 4C bottom, below freezing air. But only one dive that day (our 2nds froze and free-flowed on surfacing, and we had no way to thaw and dry them properly for a 2nd dive).

Since then, I've switched from a tight neo suit and wetgloves to a trilam, a thick and warm undersuit and drygloves. But freezing 2nd stages still put some limitations on multiple dives when the surface temps are below freezing.

 

[dewdropsonrosa]

Jared0425, what's the temperature in the Great Lakes?

In Lake Michigan (where @Marie13 and I both dive), bottom temps are typically in the range of 5-10ºC (41-50ºF), although it's not wildly uncommon to experience temps of 1-3ºC (35-38ºF) when the currents are in a mood.

 

[Jared0425]

In Lake Michigan (where @Marie13 and I both dive), bottom temps are typically in the range of 5-10ºC (41-50ºF), although it's not wildly uncommon to experience temps of 1-3ºC (35-38ºF) when the currents are in a mood.

Same thing in Lake Huron. Lake Superior I’ve gotten 36° on the bottom in May. That was the coldest I’ve ever been. Even the ice diving I’ve been doing doesn’t seem as cold as that dive was. It was miserable.

 

[W W Meixner]

In Lake Michigan (where @Marie13 and I both dive), bottom temps are typically in the range of 5-10ºC (41-50ºF), although it's not wildly uncommon to experience temps of 1-3ºC (35-38ºF) when the currents are in a mood.

Marie...others...

Kelly at Divers Den in Tobermory does not bank premix...no blend stick...filled by math...and ''very'' accurate...

All NITROX fills are partial pressure fills...cylinders/valves need to be oxygen cleaned...you need self analyze your mix and complete your entry in the shop's NITROX logbook...you can use the shop's analyzer or use your own...I always carry my own...

To dive the Arabia and the Niagara II your best mix is 30%...to dive the Forest City...in order to visit the top of the stern railing your best mix is 28%...the stern of the Forest City at the keel rests at approx 150 ft...the Forest City lies on a very steep incline...almost a ''wall dive'' with a ship wreck attached to it...

30%@ 1.4 ATA = MOD 120.9'......32% @1.4 ATA = MOD 111.3'......28% @1.4 ATA = MOD 132'

The main deck on the Niagara II is just shy of 100'...the Arabia is in the 119 ' range...the top of the stern rail on the Forest City is approx. 130'...

Advanced dives are conducted in the AM...Arabia/Forest City/Niagara II...shallow OW dives are conducted in the PM...Sweepstakes/City of Grand Rapids/W. L. Wetmore...etc...

In Little Tub Harbor...there is a ''walk-in'' shore dive area called the ''Tugs''...of which there are four...''the Alice G''... is certainly worth the visit...dropping down along the ''canyon'' on the swim to the Alice G. is quite beautiful...the pock-marked ''dolomite'' is very impressive if you've never seen it before...

Last season was unusually warm...temperatures on the Arabia and the Forest City were almost 60 degrees F...July through the middle of September...because of its location...due to a cold bottom water down wash...the Niagara II remains frigid...only 6-8 degrees above freezing all season...

Is NITROX ''recommended'' on the advanced wrecks...absolutely...I also strongly recommend slinging bailout...filled with either 21% or your MOD mix...remembering to re-calculate your ascent stop times if your breathing from bailout with a blend other than your MOD mix...

If you're renting steel tanks from Kelly...her supply is limited...reserve ahead of time and specify valve needs as some of the steel tanks have non-convertible yoke valves...

I don't dive open circuit...my bottom times on the Arabia...Forest City...and Niagara II are usually in the half hour range...

Tobermory lodging...I highly recommend ''Adventure The Bruce Inn''...

Hope this helps all who may be interested...

Happy New Year...

Warren