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So it seems like when Po2 is assumed to be 1.4 then MOD for pure oxygen is 13 feet but when we assume po2 of 1.6 then it is 20! A 7 foot deviation seems a bit too much so can anyone explain how deep can you be while you decompress on pure O2? Thanks.
I would recommend a good intro to tec. Class if you have not already taken one and if you have taken one take another as this should have been covered in said class..
1.4 is typically the recommended pp02 limit for any gas used during the bottom phase of a dive (sometimes 1.3 or even 1.2 is used). During the decompression phase when nitrox or 02 is used as a deco gas then 1.6 is the recommended limit - so yes, that gives you an MOD of 20 ft. In the past I believe the Navy was using 2.0 as the limit and of course in a chamber or on surface the limit can be above 2.0 but that is done very gradually and with medical supervision. An O2 hit on the surface is obviously not as dangerous as during a dive.
I use O2 @ 20 feet regularly and have used O2 in camber down to 60. Perform air breaks every 12-15min to better manage your exposure and deco efficiency.
On diving HMS Repulse the deco bar was affected by current and set at 6 metres but while we were decoing the current dropped off and the bar dropped to 7m (23') and my shearwater started telling me I was going to die.
Fate stepped in (along with some common sense) and I managed to get back to 6m and survive.
In the hyperbaric chamber, they had us on 100% O2 at 22m equivalent depth. This was with a critical care nurse, a crash cart and a whole heap of monitoring gear taped to me. Not a lot of fun, and certainly never something I'd try in the water.
Posting from my iPad, please excuse unfortunate iCorrects.
I toxed in a chamber at 60' on O2. No bueno, and I do not recommend it.
Breathing O2 underwater at a PO2 > 1.6 (20') is a foolish game. Some people may have gotten away with it, but there are several dead guys that did not. The reasons why chambers provide O2 at 60' is because (a) you're less susceptible to toxing while dry, and (b) if you do tox, you're not going to drown.
BTW -- no one is completely sure why you're more susceptible to toxing while wet, but I vaguely recall some people hypothesizing that the mammalian diving reflex may contribute to it.
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