Quote Originally Posted by rdkelley View Post
Looking at the shock containers I had 2 scoops of sodium dichloroisocyanurate dihydrate (99%) and one of Calcium hypochlorite (78%). Got a whiff of this in the process and can say it was life threatening to breath (no joke). So, is mixing these a known bad thing to do?
Yeah. It's known. It could have been worse, actually.

What we tell people -- consistently -- is that they should NEVER mix chemicals outside the pool. You could have added both of those to your pool with no problems IF you'd done so separately.

There are more pool chemicals that can NOT be mixed safely, than can be mixed. Borax is one of the exceptions: it can be mixed with most things -- but the ONLY time you'd have a reason to do so, is when you want to add borax and have tabs in the skimmers. With borax, you don't have to remove the tabs first: with all other chemicals, you do.

Fortunately, some of the pool gases (chlorine, nitrogen trichloride, hydrogen chloride (muriatic acid)) are seriously IRRITATING before they are dangerous. I think ozone is an exception, since I believe it can be dangerous before it really bothers you.

But, the general rule is:

Never mix chemicals outside the pool!