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Manos, If I understand your question correctly you are asking which deco gas is the most efficient for your dive if you only carry one gas. Keep in mind I am not advocating the use of only one gas for your dives. I would probably carry both 100% and 50% or at least have 100% via surface supply and hopefully you are not diving air to 55m. In my opinion you are better off using 50/50 for most dives. When? Starting at the 70ft stop all the way to the surface. There are several reasons that come to mind: 1)Deep Stops & The Oxygen Window - You get on the 50/50 as soon as you begin decompression. This opens the "oxygen window" by breathing a 1.6 and allows the tissues to off gas the nitrogen sooner into the dive. Not only do deep stops improve the way your body decompresses, they can benefit you in an emergency situation should you need to help your buddy towards the surface or shorten your decompression for any reason. You are far less likely to bend if you have completed deep stops. Ascending all the way to 20ft on your back gas and them slamming you body with 100%O2 is not necessarily the best way to decompress. 2) CNS clock - You are only breathing a 1.6 for about 5 minutes at 70ft then the po2 is decreasing through the rest of the stops, instead of breathing a 1.6 for the majority of the decompression time as with 100%. 3)More Gas - I don't look at filling/mixing 50/50 as a negative. If I am carrying 50/50 bottle on my first dive you can bet it's filled to 3000psi. Unless you have an oxygen safe booster (haskel) you will rarely have full deco bottles of 100%. More gas is good for you or your buddy in an emergency situation. Of Course there are also a couple of benefits to using 100% but in my opinion none outweigh the benefit of deep stops and maximizing deco through all the stops. To truly maximize deco you would need both 100% & 50%. Try not to get hung up on a couple minutes here and there when comparing the mixes. The quality of the decompression is most important, lastly no computer program even deep stop based "decoplanner" will spit out the truly best deco schedule. They are just a guidelines. There are far too many variables / unknowns when it comes to deco. Hope this helps. DSAO, Darren -----Original Message----- From: Manos Manoli [mailto:cytech@ma*.co*.cy*] Sent: Friday, August 31, 2001 2:31 AM To: techdiver@aquanaut.com Cc: Gliviak, Jozef; techdiver@aquanaut.com Subject: one deco gas - N50 or O2, when? OK ! I think that still there where no clear answers on Jozef question which was my question as well. What we got was mostly what everyone was using rather than why. I run several scenarios on Deco-Planner with depths from 40-55m It seams that the 50/50 benefits over O2 only a minute or 2 on short dive times in the range of 40-50m where stops below 6m where short. Further more on longer dives ( 30-40minutes ) the difference was bigger 50/50 was getting you out of the water 10 -12 minutes faster. I personally like to curry the O2 on 40-50m dives mainly for 3 reasons. 1: It like to breath it on surface if anything gets screwed up. 2: Im worried of over-loading my cns clock just before getting to the last 6m looong stop. 3: Most of my dives are in the range of 40-50m so i don't have to blend 50/50 all the time. In the other hand : 1: If i use 50/50 im out faster 2: If im using 50/50 and making most of my deco in the range of 21-9m then don't i end up with less microbubles ?????? Rgds Manos Manoli Limassol-Cyprus www.smiley.cy.net/cytech Amount of quality dive time means far more , than any number of dives and any number of C-cards. Manos Manoli wrote: > Right ! Can we have all the answers in public pls since this one im > sure its a popular question. > > Gliviak, Jozef wrote: > >> Hello guys, >> >> Recently we had a disscussion with a few friends where some of them >> advocated usage of N50 instead of O2 typically for dives like >> 55m/15min. My >> opinion would be to choose O2 rather then N50. >> Can you please answer me if there are a situations when it is more >> appropriate to use just N50 instead of oxygen. Please add a few >> examples of >> dives where would you choose O2 and where N50 as the only deco gas. >> >> Best regards >> >> Jozef Gliviak >> Slovakia >> >> ----------------------------------- >> The answer I received from George is too general for me to see where >> is the >> effective border >> Trey: >> Depends on the bottom gas. Oxygen if the dive is shallow, 50% if it is >> deeper . The idea is to get good deco at all the intermediate steps, >> relieving the need for oxygen up high. Go by the bottom gas and the >> time. >> Add gases as needed. >> -- >> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >> Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. >> > -- Rgds Manos Manoli Limassol-Cyprus www.smiley.cy.net/cytech Amount of quality dive time means far more , than any number of dives and any number of C-cards. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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