There are several distinct classifications of safety signs in common use today. Most must contain a symbol or pictogram and be of a specified colour which plainly describes its significance. There may also be text used to facilitate comprehension, but text-only signs are permitted only in limited situations.
Mandatory safety signs point out that a specific order must be obeyed. If a pictogram or symbol is used, it will be white on a blue disc. If the sign is only lettering that will be black on a white background. Signs that prohibit an action will have a red slash line and circle over a black symbol, and can be with or without text. Warning signs give notice of a hazardous condition that is probably not potentially lethal.
The usual shape is a black triangle with a yellow background and a black symbol. If these safety signs have wording, it is in black lettering. More critical red, black and white danger signs warn of a hazard that can possibly be life-threatening. Emergency signs explain the whereabouts of, and routes to, emergency associated amenities such as fire exits, first aid kits and other safety equipment, like gloves, goggles and ear guards.
These safety signs have a white symbol or text on a green background. Fire signs have a white symbol on a red background and list the location of fire extinguishers, hoses and alarms. Information signs communicate information of a general nature in order to avoid misunderstanding or confusion.