Are siltouts inevitable?

I was reading another thread where someone said that, in an out of air situation, you were going to silt the cave out, anyway. I dove with somebody last year who maintained that one of his instructors had told him not to worry about trim during valve drills, because in the event of having to do a valve shutdown, "You were going to silt the cave out, anyway." (It's unclear if anybody actually said this to him, but he had come away with it, anyway.)

My cave instructors, all five of them, would not have been happy with me, had I responded to ANY drill, simple or cascading, by disturbing the viz. Some probably would have strangled me with my own long hose if I had :) Now, I know those are drills, and real problems are much more stressful. Since the worst problem I have had so far is a dead light (and I didn't silt the cave out getting out my backup) I don't know what I would do in the event of a real emergency.

So I'm asking . . . for any of you who have had to do a shutdown or share gas with somebody, did you silt out the cave?

It was made pretty clear to me as well that a valve shutdown was not an excuse for a silt out.
That said, I have not yet found it necessary to do a valve shutdown in surroundings where this could present an issue, although there is certainly cave where I would see it as a significant challenge (for me anyway) common sense tells me, Even in that scenario minimizing the mess is only going to benefit you as you get underway again
I also find it easier to maintain a sense of direction if I maintain proper bouyancy

Siltouts are inevitable in some caves - definately. Atleast if they're going to be explored...

Siltouts are not inevitable in large, wide open passage, in most emergencies. In tight, confined passages, things are different... If you're inline in a passage not big enough to helicopter around in, with a ceiling too low to flip cleanly in order to turn around, would you not push through the silt to get some much needed gas?

As a cave diver, you better be able to deal with your junk sans visibility. Despite how good you and your team are... you have no control over others.

Siltouts are a factor of several things. The probability of a siltout goes up based on the presence of those factors. A few examples might be:
-silt. Can't have a siltout when the cave is hard rock all around you. There are some high flow bedding planes that have little to no silt, for example.
-size of the tunnel. If there is 10 feet of silt on the bottom of the floor but the tunnel is 300' tall, then unless you are skimming along the bottom, you could conceivably swim like an OW diver and not make a mess.
-Closeness of the diver to the silt. See above.
-stress
--from an emergency. Perfect trim can fly out the window if the emergency is severe enough. For example, if my buddy gives me the OOA signal, I'm going to get to him and fast, and my frog kick will modify into whatever it needs to be to get a working 2nd stage to my buddy's mouth.
--from equipment. For example, I consider myself to be a pretty good diver. You can ask a recent dive buddy, I think I handled a first stage high pressure seat failure, with a scooter, in pretty good trim. However, I once stirred up some silt in a reasonably wide tunnel, trying to clip a stage bottle back on, in pretty high flow. Something kept getting snagged somewhere and I was finding it very difficult to get the boltsnap to clip onto the doorhandles on my Nomad, it took several tries, I had other gear to handle that was getting blown around by the current, and I stirred up some silt. It wasn't bad, you could still see fine, but silt happens.

There is plenty of tunnel out there that you silt out even when everything is going fine. You don't usually see much of that tunnel in class, because a lot of it would make an OOA drill impossible. Once you get out of class and start doing some "real" diving, you'll encounter silt outs even as a top notch diver. I think some teachers might struggle to understand this concept because it has been years since they dove in something other than a "training cave." :)

That said, the attitude of "it will happen so I won't try to prevent it" is careless, foolish and immature. No matter what, I will always do my best to keep contact with the cave, including its silt, to a minimum.

More than a few of the caves I have dived over the last 2 years will always have great vis going in and poor going out. When the ceiling is, say, four feet tall, a perfect kick will send the motion up. Problem is that the motion hits the ceiling and has nowhere but down to go. But, you expect that and deal with it in a low flow silt covered passage.

In a situation where you have an issue, you would hope you could remember to get bouyant (yes I understand it may be OOA) and stick to the ceiling. If you are already trimmed right it shouldn't take much to get there, but may take a burst or a breath to make sure to are "pinned" there to work out your problem. And that of course has to do with what kind of cave you are in and how big of an emergency it really is. Damage vs my life, or damage vs inconvenience. In Mexico I am sure that is not a good option because of formations. A lot of Florida caves are the same way for different reasons.

If your skills are good and the cave is not too small than a siltout is not always inevitable. I don't imagine that the vis will stay perfect either in this kind of a situation, but I am not talking about causing damage either.

i didn't get the feeling that my instructor thought 'why bother doing the drills in trim since you'll silt it out anyway', but more 'if there's a big enough emergency that you're doing emergency things, there's a big enough emergency to get on the line'. he *did* say that in a real lost line, arm sweep that cave all you need to!

so, yeah to most op's - plan for the worst, hope for the best.

In exploration silt outs and zero viz exits due to percolation are almost always guaranteed, actually every exploration dive i have done in virgin caves has been a zero viz exit, some caves here on the first initial dives you only had a few seconds to make tie offs before a rain of silt from the ceiling would totally engulf you obscuring everything.
In an emergency it could be lessened if you can deal with the situation in a controlled manner and maintain as good buoyancy as possible, in a real emergency this could be easier said than done.
In a known cave emergency the silt out could be lessened by staying close to the ceiling and maintaining good buoyancy.
In an exploration dive emergency you probably would be in a low to zero viz situation as percolation would be raining down on you already and being still just makes the siltout that much worse, just expect it and be ready.

I think it's pretty clear that, if you're in cave where just DIVING it is going to reduce the viz, an emergency isn't going to make things any better. It's just this idea that any acute, severe stress is going to result in a siltout that puzzles me. In my Full Cave, we did some failure scenarios in fairly small places (including me getting a post failure when I was wedged in a restriction, which I thought was a very fair kind of drill) and neither I nor my buddies did any damage to the viz that we hadn't done just by passing through. But since we knew these were drills, I thought I'd ask the question of folks who have actually had to deal with serious problems, as to whether they were able to solve their issues without destroying the viz or not.

From a couple of light failures I've had solo in quite silty smallish backmount passage, everything went fine with a quick switch to backup and no loss of trim or viz. While some stress was certainly present when the lights went out, it wasnt as bad as I might have imagined though.

With some kind of massive low pressure gas escape kind of situation, pretty much all of the caves I dive in would turn to soup as the ceilings are generally soft and silty. Wether you maintain trim or not in that situation while you shutdown/isolate etc would make very little difference. Big well travelled rooms with the silt on the bottom of course would be something else.

For me its obvious that all drills, especially valve shutdowns should be done maintaining trim, as I can't see a situation where being trimmed would make things worse/slower. When those skills are required in reality trim may or may not make a difference.

Quote:

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Originally Posted by LCF

It's just this idea that any acute, severe stress is going to result in a siltout that puzzles me.

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I think what most of us are saying is this statement isn't true. A more accurate statement would be "any acute, severe stress is going to atleast slightly raise the probability of a diver taking actions that might have a tendency to reduce the visibility in the cave."