NFPA 704 is a standard system for the identification of the hazards of materials. In addition to labels on specific hazardous materials containers, personnel might see markings on fences or doors to identify general hazards of storage areas.

The NPFA 704 label is very specific. It is a diamond shape divided into four quadrants. Each quadrant indicates a different hazard rating.

• Red quadrant indicates flammability hazard
• Blue quadrant indicates health hazard
• Yellow quadrant indicates instability hazard
• White quadrant indicates a special hazard

Within the red, blue, and yellow quadrants is a hazard rating number. This number can range from 0 to 4, with 0 being no hazard to 4 being extremely hazardous.

Because the white quadrant indicates special hazards, the marking in this area will be either blank for no hazard or an abbreviation or symbol indicating a specific hazard.

Two of seven authorized symbols may be displayed in the Special Hazards diamond. (NFPA, 2007).

• An “ALK” indicates an alkaline is present.
• An “ACID” indicates an acid is present.
• A “COR” indicates a corrosive.
• An “OX” indicates that the material, by providing oxygen, can cause the combustion of other materials.
• A “W” indicates that the material violently or explosively with water.
• A “W OX” indicates the product reacts violently or explosively with water and is oxidizing

If more than one chemical is at a location, the NFPA diamond indicates the overall hazard at the location, not just the hazard from a single chemical.

The diamond shows the highest of each of the four hazards on the placard. For example, one chemical may be the highest fire hazard while another chemical may be the highest instability hazard.