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Wow, The problem with dives below 200 to depths to 300 is due to high PO2 (risk of convulsion, unconsciousness, blindness and other sutle symptoms), Narcosis (numbness, inability to do multitask problem solving, indivdual reactions that may be severe enough to put you to sleep and other well published symptoms) carbon dioxide retention, due to densisty effects and possible controlled breathing plus if you are not physcially fit you will retain up to 50% more co2 . All three of these gases effect the central nervous system and all three are additive therefor you are at a great risk of deep water bnlackout. The only safe way to explore these depths is by using mix. The biggest disadvantage of diving to these depths is people frequently die doing it Tom Mount You wrote: > >While discussing the use of nitrox mixes EAN32,EAN36,EAN50 recently a friend >of mine made the joke that he was surprised that a mutual friend who had >been diving to approx. 235fsw wasn't using a 90/10 mix ( DAN10 - Depleted >Air Nitrox ;-) ). > >Continuing this line of thought leads me to the following suggestion which >( having seen what happened to other threads ) I am sure the list will rip >apart at it's leisure. > >Add additional nitrogen to a standard scuba cylinder to produce a mix >with a ppO2 of .16 ( On the surface this is equivalent to being ventilated >with expired air from a someone attempting to resusctitate, i.e. you can >survive on it but its ideal.) > >At 10fsw you now have a ppO2 of .21 ( shallowest stop depth ) >At 300fsw you have a mix with pp02 of 1.6 ( maximum recommended ?) > >Also at 300fsw you have an equivalent air depth of 315fsw. > >So on the face of it for a ( .84/.79 = 1.06 ) 6 per cent increase in >ppN2 you get a ( .16/.21 = .76 ) 24 per cent decrease in ppO2. > >There are some obvious issues raised by this propostion. Obviously deco >times will be extended by higher ppN2. Surely the use of 50/50 as a deco >mix could mitigate this. There has been mention on techdiver about >micro-somethingorother damage caused by high ppN2 and so I guess that >this could be exacerbated. Other issues I am sure you will raise >youselves. > >The crux of the issue that I am interested in is what is the biggest >problem with deep air ( 200 - 300 fsw). Is it narcosis ( which although >the tolerance idea seems to be out of the window seems to be something >which can be 'coped' with given that the dive is planned to avoid >complication, both with task and equipment ), or is it oxygen toxicity >which has the disturbing element of poor predictability ? > >Cheers, > >Andy. > >Andrew.Hall@ma*.ac*.uk* > >There are old divers, and bold divers, but there are no old,bold divers ! >( Or at least they're a very rare breed ! ) > >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. >
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