NFPA 704

The standard provides criteria for assessing the health, flammability instability and related hazards presented by short-term, acute exposure to a material under conditions of fire, spill or similar emergencies. A number rating system of 0-4 is provided to rate each of the four hazards on a placard and provides emergency responders with information to determine immediate actions in an emergency. Tables in the standard provide criteria for the ratings and placard specifications such as letter size and arrangement of numbers and colors.