I tell my students that the standard black and white sink line chemicals are comparable to those found under the kitchen sink. Avoid skin contact, keep your face away from the tray and wash up after a darkroom session. Flush any areas that suffer contact with plenty of water. I then explain that mixing household products also have hazards, such as mixing bleach and ammonia which can be fatal and that certain chemicals used in advanced processes can have a similar reaction, such as ferric cyanide and acids. When working with chemicals always proceed with caution.