Nitrox - What do you dive PO2 - 1.4, 1.5 or 1.6?

[uncfnp]

uncfnp - being from NC how do you determine your MOD then? 1.5 or 1.4 to the sand or the deck of what you want to dive or are you diving reefs?

Great question and I wish I had a highly experienced answer for you but both my attempts to dive my own coast were blow out by storms.

Most of my diving is Florida and the depths are fairly well known in advance so no real risk of getting caught on board with too hot a mix. Once I did though so I just stayed around the 1.4 MOD. Most of my Florida diving is reef and I usually stay near the top if there is a ledge but willing to briefly drop deeper. I like to know the 1.6 depth as a contingency but honestly most of the time I'd have to get out a shovel to reach this and if I did I'd make darn sure it was brief.

The problem with NC and probably NE Atlantic is not knowing a hard max depth when selecting tanks so you have to plan for at least the most likely possibilities. Plus if I'm diving NC I'll almost certainly use a deco mix, so my plan would be sand 1.4 and deco 1.6 but I know that very little of my time, if any would be sand so would not even hit 1.4 max. Hitting sand would just shorten my dive time.

My choice to set the computer at 1.5 is from my Nitrox course and if I should decide to dive after that lobster my computer won't yell at me. But IRL I very seldom hit 1.5 and then only briefly.


Edit: If I were diving NC recreational only and if it's an option, I would look at the most likely wrecks and the depth that would give me the most intesting dive and max my bottom time then plan 1.4 at that depth.

 

[SubAquatix]

Great question and I wish I had a highly experienced answer for you but both my attempts to dive my own coast were blow out by storms.

The curse of living near the Graveyard of the Atlantic!!! with a 50% hit rate from Raleigh, it can be depressing at times!! My hit rate is closer to 80% here in the coast!!

Basking Ridge. Most of our known wrecks here have an identified Hard Deck, and it is provided to the diver when he books his charter. If a trip is adjusted, the smart captains always adjust shallower to keep things safe. The "younger" Nitrox divers will all dive specific blends based on their MOD. I always giggle when someone comes in and wants 31% or 34%. I've had more than on ask me to dump their 30% and put in 32%. For 3 mins on a recreational dive?? Ignoring the fact that they are wasting gas, while you may get a couple of minutes more, it's just easier to standardize.

 

[dumpsterDiver]

The curse of living near the Graveyard of the Atlantic!!! with a 50% hit rate from Raleigh, it can be depressing at times!! My hit rate is closer to 80% here in the coast!!

Basking Ridge. Most of our known wrecks here have an identified Hard Deck, and it is provided to the diver when he books his charter. If a trip is adjusted, the smart captains always adjust shallower to keep things safe. The "younger" Nitrox divers will all dive specific blends based on their MOD. I always giggle when someone comes in and wants 31% or 34%. I've had more than on ask me to dump their 30% and put in 32%. For 3 mins on a recreational dive?? Ignoring the fact that they are wasting gas, while you may get a couple of minutes more, it's just easier to standardize.

Why would 34% make you giggle? That is pretty much a standard mix with many of the people i dive with.. used for depths between around 115 and 75 ft..or so..

 

[rongoodman]

I've been running my Prism 2 at a set point of 1.2.

 

[SubAquatix]

Why would 34% make you giggle? That is pretty much a standard mix with many of the people i dive with.. used for depths between around 115 and 75 ft..or so..

Our standards here tend to lean toward 30 or 32, that's all.

 

[Tracy]

Wow, standard mixes.
I fill my bank with something, analyze it, and then either use it, or tone down with air for whatever dive I may be doing. My bank tends to sit between 30 and 50% on any given day.

 

[uncfnp]

...//...For 3 mins on a recreational dive?? Ignoring the fact that they are wasting gas, while you may get a couple of minutes more, it's just easier to standardize.

Living on Oak Island those three minutes would be negligible but for many of the rest of us those minutes could be priceless!

 

[Patoux01]

Why would 34% make you giggle? That is pretty much a standard mix with many of the people i dive with.. used for depths between around 115 and 75 ft..or so..

I wouldn't call it "standard mix". That's a "regional usual mix" at best...
I could *maybe* understand people using 32 and 36 as standard. But really? 34?

My 2 cents:
CNS clock doesn't tick fast enough to be an issue recreational diving.
Slightly higher than 1.4 won't kill.
Slightly lower than 1.4 won't bend.

Just my opinion of course, feel free to disagree

 

[Searcaigh]

a. Do you know any agency that does NOT include a "couple of pages on decompression theory" in the OW class?

b. What does diving on enriched blends have at 100 - 130 feet have to do with any agency's OW class?

c. What all this discussion shows is that deep dives really need to be planned based on at least three limiting factors -- decompression status (Yes, ALL dives are decompression dives); O2 status; and consumption (including decompression regardless of it being a "no stop dive"). If one is going to dive deep, get used to the idea of "doing deco" and plan accordingly.

I would also add to c don't forget Gas Planning

 

[DaleC]

I feel old. I've never heard or thought of setting a computer to a specific ppO2.
I think about the dive before hand and determine my depth limits based on where I'm going and choose my mix based on that. My computer doesn't offer me any information during the dive as to ppO2's that I care about.