Hypo disolves better with warm water. Say 95F. The chemical reaction of it disolving will drop the temp down. No real fumes. You don't really want to raise a lot of dust up.

Surf over to Jack's chemical website. If you can't find the link I'll dig it up. The website includes formulas. Info on the chemicals. etc. If you still feel like looking into this then get the Darkroom Cookbook and read it.