Talk:Equivalent air depth

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This article is part of WikiProject SCUBA, an effort to create, expand, organize, and improve Scuba diving-related articles to a feature-quality standard.

Please note that the example given is not realistic.

Diving to 60m on 40% N2 (i.e. 60% O2) would result in a ppO2 of 4.2. This is way beyond recommended concentrations (1.2 to 1.6) and would almost certainly result in a CNS fit within 90 seconds, followed by fatal drowning.

Regards Jim Mrjimfuller 23:01, 29 October 2005 (UTC)

It seems you assumed that the dive would be on Nitrox, but diving on a gas mix with 40% N2 is perfectly realistic when using trimix. Mark.murphy 19:21, 31 October 2005 (UTC)

[edit] Concept of EAD in deco theory

Gene Hobbs has provided 3 references to the use of EAD in the literature - the earliest dating back as far as 1961. However, all of these refer to the term in the context of decompression theory - that is, the concept of planning a nitrox dive by using air tables. For example, diving to 30 metres (100 feet) on EAN36 gives a ppN2 of 2.56 bar, the same as air at 22 metres (74 feet), so the dive and any decompression schedule is planned as if it were done to 22 metres on air.

The idea of Equivalent Air Depth is thus used in two distinct areas:-

1. When diving Nitrox, the depth which may be used to plan the decompression schedule as if on air;

2. When diving Trimix, the depth which would have the same narcotic effects if it were on air.

It seems that this article really needs considerable expansion to clarify the uses of the term and tie in with the references. I'll put it on my to-do list, but any help would be appreciated. --RexxS (talk) 21:16, 2 May 2008 (UTC)

Sorry RexxS, I can not think of any scientific references that specifically address Equivalent Narcotic Depth (END) which you describe above.

If you are going to improve this article, can you please address these papers in discussion of Oxygen Narcosis. We know oxygen is narcotic, but these are the few references that apply for normal diving depths.

• Frankenhaeuser M Graff-Lonnevig V Hesser CM (September 1960). "Psychomotor performance in man as affected by high oxygen pressure (3 atmospheres)". Acta Physiol. Scand. 50: 1–7. PMID 13701420. 
• Frankenhaeuser M Graff-Lonnevig V Hesser CM (December 1963). "EFFECTS ON PSYCHO-MOTOR FUNCTIONS OF DIFFERENT NITROGEN-OXYGEN GAS MIXTURES AT INCREASED AMBIENT PRESSURES". Acta Physiol. Scand. 59: 400–9. PMID 14082611. 
• Paton WD (March 1967). "Experiments on the convulsant and anaesthetic effects of oxygen". Br J Pharmacol Chemother 29 (3): 350–66. PMID 6034384. 

Thanks Gene Hobbs (talk) 19:00, 6 May 2008 (UTC)

Thanks again Gene for your help with references. The first problem I had when I started editing was that there seems to be little recognition of the narcotic potency of oxygen. Much of this would appear to be related to loose usage of terms like 'Nitrogen Narcosis' and 'Inert Gas Narcosis' - as if nothing else could cause narcosis. As a starting point, I was able to use Roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis, but I'll spend some time looking through your provided references before I try to re-write this article. I suspect that the concept of Equivalent Narcotic Depth is just a convenient approximation to what happens when breathing Helium mixtures, so I guess I'll have to find some references in the Tech Diving literature and hope I stumble across something with a little more rigour to back up what seems to be 'common consensus'.

Regards --RexxS (talk) 01:00, 8 May 2008 (UTC)