Even the simple darkroom can be dangerous if you are careless. Packaged chemicals, used as directed, are reasonably safe. But even they can react with other things around the house to cause trouble. If you brew you own, you need to be more careful. There are several chemical incompatibilities that you need to be aware of because they can cause serious safety problems. Anschell and Troop's "The Film Developing Cookbook" gives some good guidelines and lists the more common chemical incompatibilities, as do several other photo darkroom books. Even something as simple as pouring developer into fixer can release a cloud of choking, dangerous ammonia gas. Concentrated or solid chemicals are usually more hazardous and generally more troublesome than the diluted solutions. Clean up spills thoroughly and promptly.
Originally Posted by ChristopherCoy