Deco Question

[FW]

I need a baby booster

Or a gas switch block. You could plug in the offboard O2 on deco. Just don't forget, and go back down for something on pure O2

[Line Squirrel]

Great thread guys! Thank you.

[runawaylobster]

The fact that you are offgassing makes maintaining 1.6 very difficult. Imagine all that Nitrogen or Helium you are breathing out.

I haven't done any dives switching to O2 for deco yet, but I did think about it for a dive on
the Lowrance recently but I ended up sitting out the dive (no trimix for sale in Miami ...)


anyhow so far so good, I haven't needed to.

LL

[netmage]

Mike,

Lots of good stuff in the thread... the meg makes it very easy to jack in offboard gasses,... so for that eagles nest scenerio Mike E. mentioned, jack in a 40 of O2 for the long hang and manually maintain higher, leaving more residual....

Also, an LP120 boosted to 3000psi w/ O2, and an LP108 or two w/ 21/35 (for what I do, or whatever is appropriate for the nest and a transfill whip makes quick work of prepping tanks for the next dive on a liveaboard or remote location....

Also - forget about saving batteries... when I'm up in the area I'll bring my battery kit and give you some busy work... let you whip up some AA's or LithiumC's.... I'm sure you have soldering skills... the spot welder just makes life allot easier (http://www.flickr.com/photos/netmage...7604117539266/)

I experienced the lung irritation on a liveaboard trip recently. Multiple dives every day, and by day three I had a slight dry cough... Made more of a conscious effort to balance setpoint w/ deco benefit... Pushing 1.2 on a 60' dive didn't make much sense, whereas the benefit was there on the deeper reefs.

I would not expect a single ~2:15 exposure to be enough to cause pulmonary symptoms unless you were pushing 1.4-1.6 the entire time. If you were diving allot the days prior, this should also be considered. I haven't seen formal guidance in textbooks on the subject other than 'if your doing multiple days-lots of diving - drop the setpoint', was flipping the pages on my Oxygen Hacker's, and bam, right on page 142... table 11, REPEX Exposure Limits in OTU's credited to Dr. Bill Hamilton, 1989...

[MengTze]

Mike,
My last stop is 20ft and usually run the main part of the dive at 1.1. With longer dives (4hrs) it does make a difference. I found it easier to do a good reverse O2 flush by compressing (bear hug) the lungs with your left arm while injecting O2. Then subsequently adding O2 to make up for volume. I usually end up decoing out between 1.4 and 1.5. Just watch your PO2 as you offgass into the lungs.

[Line Squirrel]

Tim,

Gregg was going to show us how to make batteries we just ran out of time...even though the shortest day of eight was 11-1/2hrs long!!!!

Can you get me a materials list with specifics (I'm not much of an electronics guy) but you need to spell out exactly what type of solder/flux, pigtails, etc.

I'll try and pick up what I can and I would be grateful if you showed me how.

Gregg is more than willing, just he's 1-1/2hrs away.

[netmage]

Tim,

Gregg was going to show us how to make batteries we just ran out of time...even though the shortest day of eight was 11-1/2hrs long!!!!

Can you get me a materials list with specifics (I'm not much of an electronics guy) but you need to spell out exactly what type of solder/flux, pigtails, etc.

I'll try and pick up what I can and I would be grateful if you showed me how.

Gregg is more than willing, just he's 1-1/2hrs away.

I have it all - just have a soldering iron - or hell, I can bring mine along... it's a radio shack cheapo...

[PacketSniffer]

Just some more data points from another CCR diver.

-Yes, maintaining a relatively higher setpoint on the shallow deco stops will be hard to obtain in the *beginning* of deco. If you watch carefully, you'll notice closer to the end of each stop, the PO2 will be easier to maintain. As everyone else said, it helps to flush often. I flush at least when reaching a new stop after a few minutes (near the shallow stops). At the end of your 10 or 20 foot stop, you should have a very stable PO2. That's one sign to look for that your deco is "thorough".

Another thing that helps tremendously is minimum loop volume. By keeping no more than what is needed for one full breath, you're not diluting the O2 as much. This will become second nature after so many dives.

- I never deco out on OC.

- I have typically run 1.2, the entire dive, for almost all of my dives. Lately, I've been using 1.0 going in and switching to 1.3 on the turnaround for long dives (2~3 hours).

- I've never experienced dry cough or lung irritation from the RB even during multi-dive liveaboard trips that were four and five days long (diving "non-stop"). To add, honestly on a 4 or 5 day trip, I'll start with clean lungs (using Virkon S) and wash them mid-way through and that's it. Same when cave diving; wash them mid-week on a 5 day trip unless something unusual happened that warrants a wash.

- Get some lithium cells (either 2 C primary cells or rechargeable AA Ni-Mh cells). I had two primary C cells that lasted at least 6 months (lots of diving) until ISC yanked them out during a firmware upgrade and then charged me for new batteries. lol ....@#%@$#%

[tflaris]

I was wondering about how the rest of you guys deco out on a CCR? And I guess I'm talking more the 20ft, 15ft, 10ft stops (depending on your philosophy).

Do you stay on the loop or switch to OC?

I noticed, actually it was taught in class to expect it, that's it's pretty much impossible to maintain a 1.6po2 for a couple reasons. The primary one obviously is that you are actually off gassing into your loop.

If you love your Meg (what at a cruel mistress she is) you will stay on the lop for a couple of reasons:

1: You now hate open circuit and dread going to it unless you have to
2: Your mistress will become jealous

Seriously

By using the rebrether you are maintining a higher setpoint therefore will have reduced deco obilagationa at the end of the dive.

Using the 1.6 setpoint on OC allowed the diver to start the offgassing process faster by switching to richer mixtures sooner.

Just my 2 cents. Stay on the loop. It is much warmer than OC. No bubbles.

[Line Squirrel]

Who, BTW, was the one that dumped all that sand & gravel on my head during our deco??? Was that you or the other goof <G>.