Mailing List Archive

Mailing List: techdiver

Message Display

Date: Sat, 19 Oct 1996 19:05:17 -1000
To: cherf@ci*.co* (Scott Cherf)
From: severns@al*.ne* (Mike Severns)
Subject: Re: 0.7 ATA deco tables vs. Air/O2
Cc: techdiver@terra.net

Scott,

I think that you are not taking into consideration that on closed circuit=
 (CC) the PPO2 (the set pont determines the PPO2) is not changing but the=
 O2% is. It grows less as you decend and greater as you ascend.=20

At a .7 set point on a CC unit you would be breathing 28% O2 at 50 feet, 31%=
 at 40 feet,37% at 30 feet and so on, as compared to a constant 21% on OC. =
 The O2% is increasing as you get shallower. On open circuit it remains the=
 same. Therefore you are eliminating N2 at a faster rate at a .7 set point=
 on a CC system than you are on an OC system.

The formula to figure the O2% on CC is to divide the set point by the ATA of=
 the depth you are curious about. Thus the ATA of 50 feet is 50 divided by=
 33 + 1 =3D 2.51 ATA.
The .7 set point is then divided by the 2.51 ATA and equals 27.8% O2.

Mike

=20

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]