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--=_ORCL_6548728_0_11919608142250540 Content-Transfer-Encoding:7bit Content-Type:text/plain; charset="US-ASCII" George, I was thinking about this again. What you need to worry about from an CNS O2 tox point of view is time versus O2 partial pressure at depth, which is of course FO2 times absolute ambient pressure. Analog depth gauges are just pressure meters, so a reading of 20 ffw on an analog gauge means the same absolute pressure at altitude as at sea level. So you are right, if I used an analog gauge, this is a really dumb question. This is NOT true for at least some computers and digital gauges (e.g., the Aladin Pro, and maybe also on the Uwatec digital depth gauge I normally use). My understanding is that these sense the decrease in atmospheric pressure at altitude and compensate for it, effectively resetting the pressure for depth = 0 from 1 Bar to < 1 Bar. This means that the absolute pressure at an indicated depth of 20 ffw is less than that at sea level. This means you could, for example, breathe O2 at a deeper depth than 20 ffw (as indicated on an Aladin Pro, and maybe also on the Uwatec gauge) and still be less than PO2=1.6. Since decompression schedules are greatly increased at depth, running the highest acceptible PO2 is a good idea. John ------------------------------------------------------------ John H. Heimann Sr. Product Manager Oracle Corporation Security Products 500 Oracle Pkwy, Box 659410 415-506-9750 (phone) Redwood Shores, CA 94065 415-506-7226 (fax) Opinions expressed are my own, not that of Oracle Corp. --=_ORCL_6548728_0_11919608142250540 Content-Type:message/rfc822 Date: 14 Aug 96 04:26:51 From:"gmiiii@in*.co*" <gmiiii@in*.co*> To:JHEIMANN.US.ORACLE.COM,<JHEIMANN@us*.or*.co*>,techdiver@terra.net Subject:Re: High altitude decompression In-Reply-To:<199608140030.RAA10408@ma*.us*.or*.co*> X-Mailer:SPRY Mail Version: 04.00.06.17 MIME-Version: 1.0 Content-Transfer-Encoding:7bit Content-Type:text/plain; charset="US-ASCII" John, call Harvard and demand your money back for that physics degree. I would insist on it. There is nobody on this list who has both an iq above room temperature and any diving experience. Try writing "Dear Abbey". -G On 13 Aug 96, "JHEIMANN.US.ORACLE.COM" <JHEIMANN@us*.or*.co*> wrote: >I have been thinking about some deep diving in Lake Tahoe, which is at an >altitude of approx. 6000'. I know that decompression profiles are >significantly changed by the reduced atmospheric pressure. What I have been >wondering is how depth limits based on PO2s are affected. At first thought, I >would think that one could breathe a given mix at a deeper depth than at sea >level, since the absolute pressure at any given depth is less than at sea >level. E.g., a decompressing diver could go on O2 at something like 24 ffw >instead of 20 ffw and still maintain a PO2 limit of 1.6 ATA (I don't want to >argue here about whether 1.6 ATAs PO2 when breathing O2 at 20 fsw is safe; >this is just an example). > >John > >------------------------------------------------------------ >John H. Heimann Sr. Product Manager >Oracle Corporation Security Products >500 Oracle Pkwy, Box 659410 415-506-9750 (phone) >Redwood Shores, CA 94065 415-506-7226 (fax) > >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. > > George M. Irvine III DIR WKPP 1400 SE 11 ST Ft Lauderdale, FL 33316 954-493-6655 FAX 6698 Email gmiiii@in*.co* --=_ORCL_6548728_0_11919608142250540--
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