Quote: (Originally Posted by
robertfondren)
Allright, full disclosure. What i've done is taken an ida72d2, replaced the dsv with one from an ida59, removed the O2 injection system, and replaced this with a normal second stage with the exhaust ports blocked. At this juncture, the only gas I have available is air. What I believe it is capable of doing is: 1. Giving me 4 breaths to each vent at the surface, 2.Giving me twenty breaths per vent at 132 feet. I have no means of monitoring the pO2 YET! The second I have my scrubber filled properly, I intend to test these beliefs. I will not be alone, and if a Mod1 class for converted ida72d2' s were offered, I would of course be the first in line.
Now that my dirty little secret is out, is anybody still willing to talk to me, or have we already reserved a space in the memorials? LOL
Whoa!
Good on you for asking before you did anything.... Im hoping the drivel Im about to spill out isnt teaching you to suck eggs....
SCR's in concept are meant to be operated with Nitrox (or trimix), never air. Why? Two reasons why air is a poor choice of drive gas;
1. You'll drop the Po2 quickly.
2. You end up with a breathing mix that is MORE narcotic than air alone.
If you're deep enough to be able to utilise the low PO2's the (1) generates, you're deep enough that you dont want to be narced.
If you've not already discovered it,
Ake larsson's site is a good reference.
This thread also has some useful calculations, although Im not sure how relevant they are for you, since you dont mention what your addition/venting technique is.
I'd suggest reading up very carefully about addition/venting techniques, since there are VERY few SCR units out there that I'd trust to operate without a PO2 monitor. I certainly wouldnt run manual like this....
Good luck, be safe!