Max. depth on Air

[DA Aquamaster]

David Evans once bubbled...
Correct me if I'm wrong, but I believe that a PPO2 of 1.4 on air is reached at 177 feet. A dive past 200 feet on air would be a PPO2 of greater than 1.7.

That seems foolish to me....

Based on what I have been taught, 1.4 is the max "safe" PPO2, and 1.6 is considered safe for "rest" vs. "work" conditions. A dive past 230 would put the PPO2 at nearly 2.0.

What's down there that people need to dive to these depths on air anyway?

When diving air, a PPO2 of 1.4 is reached at 187 feet and a PPO2 of 1.6 is reached at 218 feet. I'm not sure where you got your numbers.

My nitrox training advised a max PPO2 of 1.6. But even if you go with a more conservative PPO2 of 1.4, a dive to 187 feet on air is still reasonable, rather than foolish, by your own PPO2 standards. As for diving deeper than 187 to 218 ft, I agree that trimix makes perfect sense for both O2 toxicity and narcosis limits.

For comparison purposes, with an FO2 of 36% a PPO2 of 1.4 is achieved at 95 ft and a PPO2 of 1.6 is achieved at 113 ft. With an FO2 of 32% these respective PPO2 levels are reached at 111 and 132 ft.

Where I dive there is a lot to see below 100 ft. Perhaps more importantly there is a feeling of solitude and a feeling of actually exploring places where essentially no one else goes. Max depth in my neck of the woods is 150 feet but to be honest I would probably go to 180' on air if the conditions were right and I worked down to that depth progressively over the season.

 

[DA Aquamaster]

Kaos once bubbled...


When I say that Nitrox is "safer", I mean in terms that you absorb less nitrogen: which means less (not to say none) chance of undeserved DCS, less chance of Nitrogen Narcosis, and less chance of feeling sudden pain on the plane ride home (compared to an air diver).

If I'm to take a diving trip where all dives are in the 0-100 foot range, I would feel safer diving Nitrox throughout the week than on air, as long as I follow every safety precaution (Non-deco limits and Maximum Operating Depth) for the mix I'm using.

Nitrox is only safer if you use nitrox at some higher FO2 thant 21% but continue adhere to air NDL limits. Otherwise you are still pushing the limit for nitrogen absorbtion.

On the other side of the coin, you are increasing your O2 exposure and depending on the FO2 and depths involved may elevate your risk of an O2 hit. There isn't really a free ride with Nitrox, it offers distinct advantages but imposes hard limits that cannot be fudged or broken. Using Nitrox on mulitple dives per day at or near the depth and NDL limits of the mix involved for a week would leave you potentially at risk for both an "undeserved" DCS hit and an O2 hit.

 

[captain]

Thanks DA Aquamaster, you made my point better than I did.

Captain

 

[shhanson]

I have been to 110' in Cozumel on air, but the danger associated with diving is directly proportional to the depth. Add in the factors of cold, current and low viz, and things get much more complicated.

With the right buddy, and careful dive planning, I would push to 120', but that is deep enough for me as I like to spend more bottom time that a couple of minutes....

 

[Manfred]

Personally I've been to 200 feet on air without major problems.
It wasn't much fun, narcosis just about disabled me.
How deep you go depends on training I dive enriched air if I'm shallow, above 60feet, and want extend my bottom time or dive at altitude to make my profile more conservative.
The vast majority of my dives take place within the recreational limit. I use air for most of them.

 

[Scuba_Vixen]

Captain said to Kaos:

if you dive the limits of the mix are you any more safe than diving the limits on air. I say no.

You're obviously referring to the PO2 limits, and relative to a cns hit, I'd agree with you. BUT there's more to it than just the O2 limit. You HAVE to look at the PN2 as well. At 214' on air, the PO2 is just barely under 1.6 ata BUT, the PN2 is 5.9 ata, ... At 114' on Ean36, your PO2 is still 1.6, ... but your PN2 is ONLY 2.85 ata.

So what does all this mean, you wonder .... It's the narcotic effects that accellerate after we reach a PN2 of about 4 that increase our chances of doing dumb **** at great depth and having less ability to recover from, or even recognise, our mistakes.

That's why in an overall sense, it's far more dangerous to push the depth limits of air as opposed to nitrox.

I'm glad I lived long enough to reach that conclusion, I have a Lot of 200' air dives logged, somewher, if I could just remember, wait a minute now ....


Darlene

 

[dc4bs]

My depest air dive was about 206-208 fsw (depending on which guage you want to believe).

I looked at those guages a lot that dive because even though I had just checked a few seconds before, I couldn't remember what I had read on them...

I'm comfortable down to 150 on air in warm, clear waters. I havn't noticed any issues in the colder, dark New Jersey waters but the bottom is usualy well above 130 fsw where I dive here.

Since getting certified on trimix, I havn't been deeper than 100 on air (Normaly dove EAN32 before tri-mix anyway) but I wouldn't have any issue going to 150 on air in the tropics again if Helium were not available and there was something worth seeing at that depth.

 

[Falcon99]

I may be a newbie diver, but I still think 200 feet on air has got to be one of the dumbest things I have ever heard of.

You people are crazy.

 

[perpet1]

MarcHall once bubbled...
Nitrox 32 to 80-90 feet.
Triox 30/30 (30 02, 30 He) from 80-120.
Triox 21/35 (21 02, 35 He) for deeper.

Before switching to He base mixtures, I had pretty much given up on attempting to take pictures below 100 feet. Although I would have told you I was somewhat immune to Nitrogen Narcosis due to my frequent exposure, (3-4 dives per week below 100 feet) the quality and composition of my pictures seemed to indicate otherwise.

Marc Hall
www.enjoythedive.com
march@gue.com

It is ironic that you list "www.enjoythedive.com" and you work so very hard to dive. I am not making fun of you it is just that you seem to work very hard at making diving hard.

The question I have to ask is WHY 80-120 do you use Triox (other then you can)?

One more question, Why not use Nitrox 32 when diving 80-120 as it is safe to 130, costs less, and requires less dive planning, makes you feel better (as you did with trimix), and minimises the adverse affects of nitorogen.

To be honest air is safe to a depth of 210 and change. I do not recommend diving beyond your limits BUT the mix you use should not be a factor for recreational diving where the accepted limit is 130' which is VERY safe on air. A lot of people throw out very tech specific info but if you are a recreational diver it is all noise.

DIVE WITHIN YOUR LIMITS AND COMFORT LEVEL. If the air were unsafe, then as a recreational diver, you would have been made aware of it through your certifications. If you want to go beyond your recreational limits obtain the training to do so. There are certifications to go to 200' on just plain air "that you use to fill your car tires and dry suit with". If you are going to be going to be doing a lot of extended range diving by all means Trimix is the answer but it should have a real purpose.


Frustrated with people throwing tech diving around like a badge of honor. Tech for the sake of tech is not usually the right answer. It is a good way to say "look at me and how much I know" or more to the point "How much I can spend"


Regards,
Pete

 

[diverbrian]

perpet1 once bubbled...


It is ironic that you list "www.enjoythedive.com" and you work so very hard to dive. I am not making fun of you it is just that you seem to work very hard at making diving hard.

The question I have to ask is WHY 80-120 do you use Triox (other then you can)?

One more question, Why not use Nitrox 32 when diving 80-120 as it is safe to 130, costs less, and requires less dive planning, makes you feel better (as you did with trimix), and minimises the adverse affects of nitorogen.

To be honest air is safe to a depth of 210 and change. I do not recommend diving beyond your limits BUT the mix you use should not be a factor for recreational diving where the accepted limit is 130' which is VERY safe on air. A lot of people throw out very tech specific info but if you are a recreational diver it is all noise.

DIVE WITHIN YOUR LIMITS AND COMFORT LEVEL. If the air were unsafe, then as a recreational diver, you would have been made aware of it through your certifications. If you want to go beyond your recreational limits obtain the training to do so. There are certifications to go to 200' on just plain air "that you use to fill your car tires and dry suit with". If you are going to be going to be doing a lot of extended range diving by all means Trimix is the answer but it should have a real purpose.


Frustrated with people throwing tech diving around like a badge of honor. Tech for the sake of tech is not usually the right answer. It is a good way to say "look at me and how much I know" or more to the point "How much I can spend"


Regards,
Pete

I don't use tri-mix yet. I can't afford the training and gear yet. This is why my limit for any kind of diving is still 130 ish. Like you suggest, I use nitrox mixes to minimize narcosis and extend bottom time. (As my previous post in this thread states)

I don't necessarily agree with your PO2 planning, but that is another issue. I was trained with and generally try to keep my average depth within a 1.4 PO2 as that is what is taught for cold water diving.

Due to narcotic effects, I personally wouldn't dive below about 150 on air if I was trained. From what I know, if I were to plan a dive below 140', it would have to wait until I get Tri-Mix trained in a couple of years. I like to have a safety margin. I have spoken to "old timers" among our instructors at the shop and they described the level of narcosis that kicked in below 150' on air as no fun.

But, this is not an issue of "tech" divers wearing a badge of honor. This is a commonly asked question asked me by non-divers (although they don't know about nitrox, so the "on air" part never seems to come up). It is also a question of curiousity among divers. Yes, "tech divers" do have to have better training for this. Many of them seem to choose Tri-Mix for a reason. Many of them choose air for a reason as well. It is nice to hear those reasons once in a while.