Removing the CO2 from the cockpit: When we breathe from a dive reg, we're breathing with no (surrounding) feedback because there's no "cockpit". It's the trigger from the increasing CO2 in our blood and lungs and, to some degree, a drop in O2, as well, that gets us breathing. No cabin atmosphere required. A really experienced diver can up the CO2 ante in his or her lungs by developing a tolerance for the CO2 - skip breathing. Never was my favourite pastime.
As far as O2 and barometric pressure, I'd use a constant flow of O2 - I think ~ 1/2 a litre/min. was the magic number. I don't know how I'd monitor the cabin, however. It could very well be that ambients and current air sampling methods are incompatible. More research on my part. I'll let the group know what I find. However, our friend Dalton may disagree with me regarding partial pressures at depth.
One alternative is to forego O2 altogether and just bleed air into the cabin. The PP of oxygen should be solved, but, I'd still like to have an O2 sensor.
My plan is to remove as much moisture as I can - it kills vis on the dome and is a general pain in general for just about everything from clothing to electronics to corrosion. I'm thinking CPU fans (like a CO2 scrubber) and desiccant, of which I have loads. I don't have any numbers yet or even if it'll work well at depth.
As far as 4x the moisture, keep in mind that scuba tanks provide bone-dry air. What I'd be really curious about is whether, because of Dalton, 4x the humidity would be drawn out of our lungs as we breathe out. You bring up a good point. And dehydration may come in the back door as a side issue. I'd never thought about that.
----- Original Message -----
Sent: Thursday, October 22, 2009 12:06 PM
Subject: Re: [PSUBS-MAILIST] DeepWorker's scrubbers
I havn't quite got my head around what happens with
the life support in an ambient, but will comment in case
If you scrub out the CO2 in an ambient you take away
a physiological tool that tells your brain theres too much
CO2 & hence not enough O2. With lack of O2 you pass
out with no warning. You also don't have the added safety
feature of a barometer monitering pressure to indicate
a drop in O2 levels. You can't use the bellows add
method of Phil Nuytten wich relies on changes of cabin
pressure to add O2 in an ambient.
Jay commented that O2 monitors don't work well in high
moisture environments wich you get in ambients. ( ie at
100ft you have 4x the moisture as you have 4x the air.)
Then you have to do calculations for your depth re the
PPO2 (partial pressure of O2). You may have enough O2
at depth, but as you approach the surface the O2% can
change dramatically & you can suffer a shallow water black
You'd probably need to read up on rebreathers & diving with
them to perfect the system.
It also depends on how big your cabin is. You might find
that if you have a certain flow of O2 in you'll never run out
for your expected dive duration.
Apparently you're at a greater fire risk with higher levels
of O2 in the cabin. So watch that you're wiring insulation
is not of a material that will combust easily.
There is a discription of how to build a scrubber on the
----- Original Message -----
Sent: Thursday, October 22, 2009 9:42 PM
Subject: Re: [PSUBS-MAILIST] DeepWorker's scrubbers
For years I'd been avoiding the whole idea of scrubbers: too noisy, maintenance, etc.
After my experience with DeepWorker I do believe I've become a convert. Those fans were so quiet. And no spider mask on my head or oral/nasal mask glommed onto my face. I could breathe and talk normally. Sigh. There was even a nice breeze. It takes some of us a while.
[a] Is the DW scrubber design open to discussion - is it so simple you can share what makes it work for DW? I'd love to have a design handed to me or be steered in that direction. I did find something on the Net but it requires machining. Built originally for a rebreather.
[b] Next: would the scrubbers be any trouble in a dry-ambient?
[c] How's breathing moisture handled in DW?