How Deep Is Air Safe As A SCUBA Breathing Gas?

[DeepTechScuba]

Let's see how the divers sort out on this board.

I know what NOAA teaches.

I know what NAUI, PADI, SSI, and YMCA teach.

I know what TDI teaches.

I know what GUE teaches.

Lets see what YOU believe about this.

[Note: "scuba" means self-contained, not habitat nor surface-supplied.]

 

[nativenarcosis]

Isn't it 297 feet where the O2 in air is toxic?

 

[Genesis]

is about 215' on air.

1.4 is ~187'.

Thus, on PO2 only, the answer is 187'.

However, that's not the entire story.

My personal limit is an EAD of 130', because that's where I begin to notice narcosis impairment and begin to be concerned about the issues that it may cause in a task-loaded situation. I'm still perfectly functional at 130, but I'm also perfectly functional after a beer or two; the issue is what happens if you need immediate reflex-style responses while somewhat impaired.

I personally dive Air wherever Nitrox doesn't make sense down to a depth of 130' or so. For most dives I prefer Nitrox below 60' and at or above 130-140', simply because I custom mix my own and I am almost always doing multiple dives in a day - so for the reduced nitrogen uptake, its worth it.

Above 60' or so I can typically do the dives I want on air without using Nitrox, but again, that depends on the dive profile. I will sometimes use Nitrox on a 60' profile if I intend to do multiple dives and want them to be nice and long - say, two @ 40 minutes each bottom time with an hour between them.

You can't do that profile on air.

 

[MikeFerrara]

Could you define safe?

Divers have survived breathing I believe below 500 ft but I wouldn't do it.

 

[mddolson]

I have been diving since 1972, and logged over 1000 dives.
My personal limit on air is 120 fsw.
Below that depth I feel the effects of narcosis.
Minor changes to nitrox make no improvement.
I'm just as narc'd on Nitrox at 120 ft as on air.

Add 20% helium, on 150 ft dive to get the AED to 110 ft and I'm 100%.

My buddy claims to be completley fine at 140 feet on air.


Mike D

 

[DeepTechScuba]

Interesting question.

Youre supposed to check the box, based on YOUR definition of safe, MikeF.

 

[MXGratefulDiver]

IMO - for recreational purposes (down to 130 fsw or so), how deep you can "safely" go on air is going to vary from one diver to the next ... because our ability to cope with narcosis varies from diver to diver.

For me, although I've been down to 137 fsw on air, I would only do so under ideal conditions (i.e. warm water, excellent vis, and with a very experienced buddy). The reason is simply that at that depth, I am substantially impaired due to narcosis. The one time I did this, I was in Bali and diving with a DM. I wanted to find out what it felt like to be narced ... and I did. For me it's not a "happy" feeling ... I was damn near paranoid and I will go out of my way to avoid that feeling again.

I can typically go to 100 fsw on air without any noticeable impairment ... which isn't to say that I'm not impaired, but rather to say that my impairment is within my capacity to deal with any potential emergency situation that I might have to deal with.

Deeper than that, I prefer EAN30. Lately I've been thinking about learning trimix so I can extend my range ... at this point I still limit myself to recreational depths.

... Bob (Grateful Diver)

 

[Walter]

It depends on the individual, their level of training, their experience and the conditions that day. The vast majority should never exceed 100 fsw. I don't check boxes in these silly polls.

 

[drbill]

Some of the divers (and most of the non-divers) I've met are impaired breathing oxygen at the surface! In my cool temperate diving environment here, I feel fine down to 120-130 ft, but generally don't go deeper than 100 ft unless there is something specific (biologically) that I need to view or video. In the tropics I occasionally go to 150 ft. I prefer bottom time over depth any day.

Dr. Bill

 

[BKH]

I normally dive between 130 and 160 fsw on air. My deepest so far is 177', with no narcosis effects to date. I'll probably not go below 200' on air...