As long as you use eye protection and don't breathe the fumes, you'll be fine. I have had it splash on my hand before, but if that happens you just dunk it in the pool and wash it off, and it's no big deal. You can retest after adding the dry acid--give it an hour or so to circulate, and then test again, and then add your muriatic if you need to. After adding the MA, again let it circulate for an hour or so before testing for pH again, and you can continue this until you get the pH where you want it. You can add bleach within 15-20 minutes after the acid addition with no problems. When I use either bleach or MA, I pour it very slowly into the return stream in my deep end, so the jets help mix it and disperse it around the pool. So once you've added the MA, you just want enough time to make sure it's been pushed away from the addition point before adding the bleach. The same goes for swimming--just give it an hour or so to make sure there aren't any "hot pockets" of bleach or acid in the pool, and it's fine to swim.

You can buy replacement CYA reagent online at several places, including amatoindustries.com, taylortechnologies. com, or spspoolspas.com (that's where I get mine).

Don't rely on the test strips for CYA--they're just not reliable enough.

Janet