The NFPA 704 label is diamond-shaped, and is divided into four parts, or quadrants.

The left quadrant is blue, and contains a numerical rating of the substance’s health hazard. Ratings are made on a scale of 4 to 0, with a rating of 4 indicating a severe hazard that a very short exposure could cause serious injury or death. A zero, or no code at all in this quarter, means that no unusual hazard would result from the exposure.

The top quadrant of the NFPA symbol contains the substance’s fire hazard rating. As you might expect, this quadrant is red. Again, number codes in this quadrant range from 4 to 0, with 3 representing a serious fire hazard. See Figure 2-1.

The NFPA label’s right quadrant, colored yellow, indicates the substance’s likelihood to explode or react. As with the health and fire hazard quadrants, ratings from 4 to 0 are used to indicate the degree of hazard. If a 2 appears in this section, the chemical is moderately unstable, and even under NORMAL conditions may explode or react violently. A zero in this quadrant indicates that the material is considered to be stable even in the event of a fire.