Hi Stephen

though I don't know all the answers to your questions... I'll look it up in my text books tonight (in other words you've got me thinking you might be right and I might be wrong on the airconsumption... but that is what you are taught!) and confirm.

Now as to why it doesn't last longer than a breath at the surface. As the density of the air increases so does the amount of gas, which is absorbed in to the blood, so essentially you are still exchanging gasses at more or less the same rate, just in greater density. This is one of the reasons why at deep depths (generally around 30 meters) nitrogen narcosis sets in due to the amount of nitrogen absorbed in to the blood (and subsequently saturates your bodies tissues too).

I’ll check the air compression rates a depths out when I get home tonight and let you know.

Thanks

Mike