In a basic darkroom, what is the danger level? What could possibly happen?

For instance, I've got three chemicals - Dektol, Kodak indicator stop bath, and Fixer. How harmful are those chemicals really? (other than ingestion or eye splashes?)

Is Dektol going to eat through the skin? Countertop? Will the combo of Fixer and Dektol create a toxic gas?

Its awesome that you put out a public warning as a chemistry teacher, but for those of use who are absolutely NOT interested in studying chemistry, WHY is safety important? What kinds of accidents are possible with basic chemicals?