The 120 rule



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Posted by TDI_2 on May 08, 2002 at 15:02:54:

In Reply to: Re: This sounds like a tempest in a teapot posted by Steve on May 07, 2002 at 22:47:17:

The 120 rule works for all gasses. The more O2 in your nitrox, the better it works, as long as you mind your PO2 depth limit.

Lets see if I can remember/calculate the PO2 depth limits for the cold water 1.4 benchmark:

air = 185 fsw @ benchmark 1.4 PO2

EAN 25 = 150 fsw [ditto 1.4]

EAN 32 = 110 fsw [ditto 1.4]

EAN 36 = 95 fsw [ditto 1.4]

Then your max time at 95 fsw on EAN 36 comes to 120 - 95 = 25 mins. Close enough, to any EAN table.

DO NOT forget egression by halves, 1 min first stop, 2 mins second stop, 3 mins third stop, 5 mins last stop.

Your wife can sue me if you die. But I think you will be very safe.

You will be safer still if you change the battery regularly in your dive computer and stick with that. My dive computer has 3 personal settings: thin, fat, and old. :)


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