mCCR and zero viz exit

Drmike

1st thing i do when running min loop is close off the adv.


with scr only your never going to go hipoxic so to me breathable loop is assured if running scr:-

choice is = risk of death from hyperoxia or inefficent deco

Id take the latter anyday, run scr and just extend deco.

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johnv

Basic practice for passing deep sumps:

take gas you need to decompress on the other side.

Drmike

really? so what will you do to read your gauges in zero vis? lights wont help.

a hud would help yes to see your ppo2 but not your depth and time, and many units dont have huds.

in real zero vis silt out no matter how many lights you have you wont be able to read your displays due to light scattering

even if you have a hud that wont help you know your deco info (unless its boris/sentinel) as you cant read your tables or your dive computer or see your own hand untill its touching your mask

bottom line for me is if zero vis is likely you need a block of perspex

always carry back up lights

a hud is nice to have but not essential and wont protect you (as this case illustrates) if your not paying attention

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caverkevin

Not everyone is doing deco in a elephant's mud puddle during a monsoon ......

I have a feeling what MT is getting at, it is very unlikely the whole dive is going to go zero and Braille exit. While it is fun to talk what ifs, think the chances of not being able to read gauges until you have surfaced are extremely small. Not being able to read a LCD display inside a low silty tunnel while cave diving are pretty high.

Cheers!!

Kevin

Jerry

The chances aren't as small as you might think; silt isn't the only thing that makes zero vis. Dive any of the N. FL sinks that aren't under tree cover in the summer and see if you can read your gauges for the algae. I dove Morgan Spring in July and all the stops from 50 up were pretty tough.

Jerry

Ben Field

Bit of real world experience from Saturday just gone...

Was 2nd dive of the day, 11mtrs max on small wooden wreck. Skipper asked me to take the shot line and make a permanent shot on something solid looking and bag up his weight.

On the wreck viz was swirling due to 8 divers on 50ft wreck on sandy clay bottom and my buddy and I's effort with the shot... varied between maximum 30cm to 5cm or less.

Working hard in shallow water I started the job at about 1.0 PPO2, torch was pointless, although buddy had hers on held over the site to give some idea of up/down, did mainly by feel.

Task took about 10minutes in total (skipper had tied the shot and line together far to well!) I let the PPO2 drop to 0.7 or less each time before injecting O2, the Shearwater HUD light intensity change at + or - 0.3 from 1 is very distinct- flash, flash.....flash, flash, flash.....flash, flash, flash.....FLASH, FLASH, FLASH.... OK, hit MAV.

My HUD is DSV mounted and after both dives in appalling viz I won't be moving it, despite the crap in the water it was pretty obvious what the PPO2 was doing. (FWIW, I flooded my mask jumping in the first dive and I could still make it out... not intentionally I might add!)

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osiris

DITTO to the last post - mid last year I had a very similar incident to the case first described following a buddy in a local lake aptly nicknamed "Lake Poo". Normally the viz is quite acceptable below 10M, however my buddies contrail put me in the middle of thick cloud of extremely fine, smoke like silt. Not being equipped with HUD, I could see nothing of my KISS displays or my VR3 even right up against my mask. WHile I knew at the time I only had to ascend a couple of metres to get out of the SH, it was disconcerting nevertheless. The key to this is at the time I was not prepared for the total blackout and the potential in respect of PPO2 monitoring - I basically couldn't monitor my sensors at all. I ahve dived that lake heaps of tiems and not experienced the same thing but I wan tot be sure that I can cope the next time it might happen so a HUD seems poretty important - so does Dr Mikes perspex.

Drmike

i dont disagree - as you will see if you read my earlier posts in this thread. thats why im happy to go scr for those short periods when i cant read my displays

But the point still stands that some exits can be a braille zero viz all the way out if tight and silty cave passages with min to no flow....and especially if your behind me!!


sure not common in big tourists caves in N florida but there are still plenty of small tight silty caves around, I was diving in some recently , 5 long static silty sumps all zero viz - couldnt see sh1t, well I could, I was burried in it

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Meng_Tze

That is funny.

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Drmike

for the record i am well aware there are tight small caves in N florida too - but generally these are not on the 'tourist' list of caves

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Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you