isobaric counter diffusion is a PADI, IANTD, TDI scare tactic

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Posted by MHK on July 05, 2001 at 14:48:19:

In Reply to: Isobaric Counter Diffusion (boring stuff don't read) posted by Steve on July 05, 2001 at 14:13:57:

The one thing that I’m not sure about with respect to the isobaric counter diffusion [“icd”], is that it is much less worrisome than the Red Blood Cell rigidity issue that we hammered at a few months back and it was roundly dismissed as some tech/dir phenomenon that wasn’t worth scaring sport diver’s over.

Isobaric counter diffusion is a mythical PADI, IANTD; TDI issue that tries to explain why diving deep on air is better than using helium. It’s complete BS.

The theory is that when you switch gases, through, isobaric counter diffusion bubbles appear even though you may not be changing depth. Of course the illogical thinking is that helium diffuses faster than Nitrogen gases out and for that limited period of time the partial pressure if inert gases will increase which can cause bubbles. This is contradictory with the idiocy of using air to 165’ in case your student bolts. PADI is wrong on both sides of the issue but yet would have you scared to death over this strange term called “isobaric counter diffusion”. It’s basically designed to let you believe they have thought out the issue so you buy the other BS they are selling, but then they completely contradict themselves with the notion of the student that bolts to the surface is in trouble because He uptakes faster…

Anyway, if you have reviewed the 1979 studies out of New Zealand measuring the subcutaneous tissue pressure caused by nitrous oxide (N20), helium (He) and 1 ATA isobaric counter diffusion gas phase developments you’d know this is BS…

Let me know if you need me to expand on the studies, or maybe you have read them already…


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