What is the danger?

[Cacia]

I'm lax, but I invert a rental tank right after I splash in case there is trash at the bottom.

I realize it might not be a problem till the pressure drops, but it makes me feels better about any liquid or particles. I also try and give my reg a minute or two of devoted attention to how it is breathing.
The other thing, is if you are diving an iffy looking tank, don't invert ay the end of your dive until your deco obligation is over just in case there is crud...

I dive a lot of sketchy looking unknown tanks to be honest.
I try and size that up and at least be aware of that.

It's the kind of thing that makes you think twice about inverting and crawling through a hole....deeper than CESA, solo

I wouldn't breathe old 3 year old air---even I have my limit, it could be toxic.

 

[Coll]

an animal? now your decision is making a bit more sense. but we now have to hear this story it sounds good! so, lets hear it!

I work at a sea lion training facility and one of the lions managed to pull the bottom drain covers off, this leaves a decent sized hole in the bottom of the pool which could potentially suction an animal and trap them, in which case they would drown. It is also illegal to have an unprotected drain. Therefor, we had to put a drain cover on and I am one of the more avid divers on the staff so they asked me if I would do it.

I've tried to attach a picture of the culprit so if you ever see the young lady around your drains you can shoo her away