Is nitrox worth it for deeper rec dives?

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I'm not usually one to do everything possible to squeeze an extra minute of bottom time, but I have to agree with you on that one. The boat ride out of Morehead City is almost three hours to reach the U-352. All so you can have your few precious minutes on that wreck.


Three hours of sea sickness. I sooo wanted to throw up , everyone else did but I didn't.
 
@Stoo

Thanks for the mention that DD banks 32%. Toby's in July so I'll send an email off to Kelly to get nitrox fills in the HP100s I've already reserved.

I've got quite a few deep dives come up in the next couple of months so I decided to do nitrox as much as logistically possible and see how I feel. Just got back from picking up my doubles filled with 28% for a 130ft wreck on Saturday (Milwaukee carferry - deck is at 100ft, but the huge double props are at 130, and buddy would like to see them). 85 miles roundtrip tonight, tanks were dropped off after diving the quarry Saturday (shop is one hour from quarry, then another hour home). The only bad thing about getting a custom mix is the two 85 mile round trips and giving up half of two evenings. At least with the banked 32% I can just wait while my tanks are filled. The long drive is necessary. A shop by my office will fill my HP tanks, but they don't do nitrox at all. A shop in my suburb has a compressor that only goes up to 3000 psi. No nitrox. A buddy told me about a shop in the area that banks 36%, but due to traffic, it's even more inconvenient to get to than my shop. Remember, this isn't cave country.

I've got six dives in Lake Huron off Sanilac, MI, Memorial Day weekend (wrecks 80-100ft). I'm taking both sets of doubles filled with 32%, and get one air fill locally. A wreck with the deck at 120ft June 1 (Northerner, off Port Washington, WI, a schooner that went down in 1868), and then my long awaited three day trip to the Straits of Mackinac the second weekend of June. I'll be taking both sets of doubles filled with 28%, and get one air fill (captain has a compressor on his truck, boat is trailered to the Straits from WI). Otherwise, just lots of local dives on Lake Michigan. :D
 
I took PADI nitrox a few months ago, and have a very basic understanding of nitrox. Today I posted in a local forum (Utah Scuba Divers) some information I obtained about nitrox supplies in my state, just because it seemed interesting. But one of the local instructors seemed to suggest that expecting to be able to get oxygen clean air (EAN21) isn't something likely to happen (not that I'm looking for it, but there might be times when it would be more appropriate than 32 or 36 or something). If that's true, what are people using for air when partial pressure blending?
 
IME the blending is done from the normal air banks. I would be surprised if a shop bothered having oxygen clean banks and compressor along with one that wasn't.
 
IME the blending is done from the normal air banks. I would be surprised if a shop bothered having oxygen clean banks and compressor along with one that wasn't.

So there’s where I’m confused. The PADI nitrox manual says “If you ever need to use air in an enriched air cylinder, no problem. Take it to an enriched air fill center. They treat the fill as enriched air in all aspects, including marking it EANx21 (“enriched” air with 21% oxygen), analyzing the contents and completing all records. If an enriched air cylinder that has been prepared for oxygen service (for partial pressure filling) is accidentally filled from a conventional air source, it must be cleaned and serviced by someone qualified to service enriched air equipment before being exposed to more than 40% oxygen again.” There are also a lot of posts on this thread suggesting that air blended into nitrox isn’t the same as the air going into regular tanks, but is “hyper” or low hydrocarbon or some such thing. Do what’s up with that?
 
If an enriched air cylinder that has been prepared for oxygen service (for partial pressure filling) is accidentally filled from a conventional air source, it must be cleaned and serviced by someone qualified to service enriched air equipment before being exposed to more than 40% oxygen again.”

"Conventional air source" is rather vague. “Grade E” breathing air Is used for partial pressure blending and if that is your conventional air source there is no reason to O2 clean it again. If it is not grade E, or you don't know, then it should be recleaned. One other reason for accumulating a tank farm.


Bob
 
So there’s where I’m confused. The PADI nitrox manual says “If you ever need to use air in an enriched air cylinder, no problem. Take it to an enriched air fill center. They treat the fill as enriched air in all aspects, including marking it EANx21 (“enriched” air with 21% oxygen), analyzing the contents and completing all records. If an enriched air cylinder that has been prepared for oxygen service (for partial pressure filling) is accidentally filled from a conventional air source, it must be cleaned and serviced by someone qualified to service enriched air equipment before being exposed to more than 40% oxygen again.” There are also a lot of posts on this thread suggesting that air blended into nitrox isn’t the same as the air going into regular tanks, but is “hyper” or low hydrocarbon or some such thing. Do what’s up with that?
If your gas source is nitrox compatible, it doesn't matter.

It only matters if you have an oxygen cleaned tank and you fill from a compressor which doesn't deliver nitrox compatible air. If you only fill inline or banked nitrox <40%, don't worry. If the fill station delivers nitrox compatible air, don't worry. The fill station should be able to tell you if their gas is nitrox compatible or not. If they can't, I'd get my fill somewhere else.
 
There are also a lot of posts on this thread suggesting that air blended into nitrox isn’t the same as the air going into regular tanks, but is “hyper” or low hydrocarbon or some such thing. Do what’s up with that?

Grade E/Hyperfiltered/Oxygen Compatible Air isn't that much more expensive than running normal air. So most shops that offers nitrox through PP blending (be PP to the bank or PP directly in the customer tank) isn't going to go through the much larger expense of having an OCA air compressor/bank, and a non-OCA air compressor/bank. Now shops that offer nitrox through a membrane system, or through a stick blending process don't necessarily have to use OCA air, but many shops do. Heck I know a few air only shops that offer OCA.
 
Grade E/Hyperfiltered/Oxygen Compatible Air isn't that much more expensive than running normal air
I've yet to fill from a station which didn't deliver nitrox compatible air. Based on my experience I guess "hyperfiltered" is the norm here on the right side of the pond.
 
@Stoo

Thanks for the mention that DD banks 32%. Toby's in July so I'll send an email off to Kelly to get nitrox fills in the HP100s I've already reserved.

:DI've got quite a few deep dives come up in the next couple of months so I decided to do nitrox as much as logistically possible and see how I feel..

On the one- or two-dive days, I don't think I feel any different, but if I'm on a trip and doing 3 - 5 dives a day for a week, I find it's worth it to dive nitrox. With multiple dives over many days, all of which are at or beyond NDLs, everything I can do to reduce nitrogen uptake is a good thing I figure.

As I mentioned earlier, on local dives, I don't generally bother with nitrox, opting to sling a tank of 100% instead. Many of the dives I do are too deep for a rich mix anyway, or the increased O2 amount would be so minimal it's hardly worth it. (Having said that, two years ago I did a 175' dive on Petrie 2 with a friend. My tanks tested at 22%, his were 21%. We did EXACTLY the same profile, and he's way more fit than me, and 20 years younger... but he got a minor hit in his shoulder. Hard to imagine that 1% made a difference, but you never know. :wink:

(In fairness, he felt it after the next dive, which was about 2 hours later, to 100'. He dove an hour before I did on that dive, so that's a more likely contributing factor!)
 
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