ANSI Z535.2 2002 encourages the use of safety symbols whenever practical to do so. There are 4 types of safety symbols that communicate different messages: Hazard Alerting, Prohibition, Mandatory Actions, and Information.
Hazard Alert Symbol
This is the general warning symbol. It is used to alert the user to potential hazards. All safety messages that follow this symbol shall be obeyed to avoid possible harm.
Prohibition Symbol
This type of safety symbol conveys actions that should not be taken or should be stopped. For prohibition, use of the surround shape is mandatory
Mandatory Symbol
This type of safety symbol conveys actions that should be taken to avoid hazards. If a surround shape is desired, the symbol should consist of a white image within a solid safety blue circular surround shape.
Information Symbol
This type of safety symbol is generally used on General Safety or Fire Safety Signs to convey equipment location, egress, permitted actions and fire equipment location