BBC, freediving & bad science.


I was reading this through with interest from the Scuba angle and was rather puzzled when I got to the bottom:

Mr Harris thinks Blaine will have an unfair advantage when he attempts the world record.

"He will be breathing compressed air under water so he will have a much higher concentration of oxygen molecules," he says.

"In competitive freediving, we are positively banned from breathing pure oxygen before the event."

Can anyone explain exactly how the % of oxygen in compressed air is different to the percentage in uncompressed air?
I hope he's been misquoted, either that or he needs to resit his diving exam.
The partial pressure of O2 at depth is of course higher, but the concentration is unchanged. Unless of course he's breathing Nitrox or pure O2, but the max depth on O2 at 1.6 bar ppO2 is only 6 metres and has serious CNS issues if used for days at the surface, let alone at any depth.
As for the O2 ban, isn't that to do with why you shouldn't hyperventilate before freediving? It reduces the level of CO2 to below that needed to form the stimulus to breathe at the end of a breath hold whilst the level of O2 drops below the level needed for consciousness resulting in drowning.

I think you've probably answered your own question there!!
Perhaps what he means is that because it is compressed air, the number of O2 molecules in a given volume would be higher than that of the same volume at surface pressure.

Just a thought.
I've read it the same as you have Cornelius, he must mean Nitrox and not 'compressed air'.

Even under pressure, the % of O2 would be the same as with atmospheric air (20%), even if there were more molecules for the same volume. Also, just because there would more molecules does not mean that more O2 would be available due to the partial pressure principle (Blaine's body will also be compressed/at depth), so I can only assume that he's referring to some sort of enhanced mix/nitrox that Blaine intends to pre-breathe (which is not permitted in free-diving).

The navy boffins at Alverstoke would explain this far better than we can ?! :roll: :?

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