Is nitrox worth it for deeper rec dives?

[MrVegas]

There are sooo many threads on oxtox. Here are a few of the more recent/interesting...

Likelihood of getting oxygen toxicity at 1.4 PPO

Oxygen Toxicity Limits & Symptoms

Thanks -- I'm embarrassed to say that I actually read through and posted in one of those threads -- I guess I didn't go through some of it in enough detail. If I am reading this one DAN study correctly, the answer to my question would appear to be that there are no confirmed recreational scuba deaths in the U.S. in the last 10 years clearly attributable to oxygen toxicity seizures when nitrox was used within MOD at PPO2 of 1.6 and within time exposure limits: DAN | Medical Frequently Asked Questions There was one fatality attributed to oxtox on 32% with a max depth of 160 feet. (Again, assuming I understood the study correctly.)

I recall in the other threads there was discussion of one or two possible seizures at lower levels. I also read the book "The Last Dive" and there was a tragic story in there of a diver who died used 39% down to 135 feet, so, again, outside accepted limits.

Some of this is repetitive, I guess, so I apologize for that. I guess we all want certain answers, but, of course everyone is different, and I am realizing our bodies are pretty fine-tuned to operate at 21% at sea level. Going back somewhat to the OP's original question, although I have no inherent desire to dive "deep" just to do it, there are some dives down towards the lower end of the recreational range that I'd like to do someday, and I frequently use pseudoephedrine to help clear, so gathering this type of information is helpful.

 

[tarponchik]

It appears you are trending away from your original belief that the O2 we breath as divers damages our DNA.
This is good. Wildly unsupported suppositions are not helpful.

Once again, you have difficulties understanding the words you see on your monitor. Shall I say more?

 

[tarponchik]

It likely isn't a concern with the modern jet fighter, in the USAF the new goal for fighter pilots is 20 flight hours a month. Even at 100% oxygen at sea level, that is 1,200 OTU per a month, and the NOAA charts if you follow the suggestion of no more than 300 OTU a day, results in a maximum monthly OTU of 9,000. But that doesn't take into account PPO2, at the typical 8,000ft cabin altitude (which many military aircraft maintain up to a set altitude) that is 0.74 ATM, the OTU per a minute at 0.75 atm is 0.56, so over that same amount of flight hours they have a monthly OTU of 672 which is below even the maximum single day exposure limit.

Of course, this isn't a major concern, like smoking. The problem, as Donald Rumsfeld put it so brilliantly, is that there are known unknowns and there are unknown unknowns. The unknown unknown in this case is your genetics. Because of genetic variability, people vary drastically in their defensive capacities against damage caused by chemical agents. Some folks can smoke cigars till they die of stroke at 95, some shouldn't even sit by the fireplace. And you almost never know which pod you belong to.

This is not to say that I avoid Nitrox at all cost. I did 5 Nitrox dives in November and 2 in June. But every time I chose Nitrox I knew I would get longer bottom time.

 

[Clayton122]

@scubadada

I've not totally made up my mind, but I am going in the direction of no nitrox. My dives are either from boats on the Great Lakes or the quarry. On the boat, everyone has the same SI (at least 1 hour) and quarry dives are also always 1 hour. So in my case, the decreased surface interval benefit doesn't apply.

I always try and use Nitrox between the 60-100 foot range. The NDL time goes way up.

 

[Alan Browne]

This subject is not studied. I was not able to find any long-term studies of military jet pilots health. Civil aviation pilots were shown to have somewhat higher rates of melanoma and prostate cancer than general population, but that's all.

They sit on their butts for the whole flight (almost) (prostate issues) and are exposed to high altitude radiation (UV) since the cockpit glass is plastic and doesn't filter much UV.. (melanoma).

Recall again, a fighter cockpit is at lower pressure than sea level. So the PPO2 is going to be relatively weak no matter how long the exposure. And military breathing gas is not 100% in western aircraft. Varies from 40 .. 95% depending on aircraft type.

The cabin altitude for fighters is not 8000' generally - it varies amongst types.

8000' would be an approx. for airliners at cruise however.

 

[Stoo]

I think DD is now banking 30% or 32%...

I don't tend to bother since it means planning ahead and typically, I don't know where I'm diving until we round the point and see what the wind is doing. A lot of the dives we do are deeper than nitrox likes.

Instead, I carry 100% and do some deco. I still get the bottom time I want, but end up soaking up top a while longer. Bear in mind, I dive all of the Tob wrecks a LOT, so getting a few extra minutes isn't worth the additional effort.

On the other hand, if I'm heading away to a place I don't dive often, and if the wrecks are in that sweet spot, I likely would do nitrox. So since that's kind of what you're doing in Tobermory Marie, it might be worth it for you!

 

[Bigeclipse]

I've going to have some deeper dives (110-130ft) this coming season. I'm wondering if nitrox is worth the cost for the wee bit of extra bottom time! I ran the numbers on my Perdix (medium conservatism). At 130ft with 28%, you only get 3 more minutes of NDL time than on air.

At my shop, I'd pay $14/tank (up to 100cft tank) for custom mix (you can get banked 32% for $12/tank). In addition, I'd have to have a pair of tanks O2 cleaned ($50/tank, so $100).

Most of my diving is only 2 dives a day. Occasionally I'll do 2 Lake Michigan charters in 1 day (4 dives), but most of those are shallower (less than 90ft, most under 70ft). I have a trip to the Straits of Mackinac in June (3 days of 2 dives each) and Toby in July (1 day of 4 dives 1 day of 2 dives). I'll be taking my own tanks on the Straits trip, and am up in the air about the Toby trip (Divers Den only has 6 HP100 tanks for rent) - I refuse to dive aluminums now. Screws with my weighting.

I got a pair of tanks O2 cleaned last summer, but I really only used the O2 cleaning when I was on my Alpena, MI trip. I could have easily done those dives on air.

I've debated this with several friends and they all just do deeper rec dives on air. I didn't get my new doubles setup (tanks I already had) O2 cleaned, either.

Depends on the dive. For example I dive this lake from time to time where there are some deep spots. Many of these spots are areas where people drop stuff so ill head down to those areas quick (minding my NDL of course) and then head up. For those dives, I just stick with air as I go to those spots routinely so nothing really interesting to see and id likely only be there a couple minutes anyway. However, I went to North Carolina to do some wreck diving on some old wrecks from world war II and you want all the bottom time you can get since some of the wrecks are in the 100-130ft range. We brought 28% steel 100hps for that exact reason, specifically when we dove the German sub that sank there. This sub lives right at the 110ft mark or so if memory serves me correct and time flies when you are trying to check the entire wreck out at those depths so yes, an extra 3 minutes was definitely worth it for that dive. I do recommend 100cu tanks for those dives because they are exciting and you can suck air down pretty fast when taking pictures and such.

 

[Billy Northrup]

If you take the cost of your trip and express it as bottom time it's almost always worth it between non stop and 130. FWIW I can't do more than 2 deepish air dives in a day or I get pretty bad headaches.

 

[MaxBottomtime]

Headaches from diving are caused by skip breathing and/or too fast of an ascent. Try slowing your ascent by half and I'm sure your headaches will go away.

 

[Bob DBF]

On a square profile, you just have to figure if the two minutes are worth the money for Nitrox. With a multilevel dive it's much easier to justify.

For looking I'd just stick with air, for salvage the two minutes could be handy. Not your situation, but just saying....


Bob