NFPA 704-2001 Standard System for the Identification of the Hazards of Materials for Emergency Response.
4.1 Description. 4.1.1 This system shall identify the hazards of a material in terms ofthe following three principal categories: (1) Health (2) Flammability (3) Instability 4.1.2 The system shall indicate the degree of severity by a numerical rating that ranges from four, indicating severe haz- ard, to zero, indicating minimal hazard. 4.1.3 The information shall be presented by a spatial ar- rangement of numerical ratings, with the health rating al- ways at the nine o’clock position, the flammability rating always at the twelve o’clock position, and the instability rat- ing always at the three o’clock position. 4.1.4* Each rating shall be located in a square-on-point field (commonly referred to as a diamond), each of which is as- signed a color: (1) Blue for health hazard; (2) Red for flamma- bility hazard; and (3) Yellow for instability hazard. Alternately, the square-on-point field shall be permitted to be any conve- nient contrasting color and the numbers themselves shall be permitted to be colored. (See Figure 9.1(a) through Figure 9.1(c) forexamples ofthespatialarrangements.) 4.1.5 The fourth quadrant, at the six o’clock position, shall be reserved for indicating special hazards and shall be in ac- cordance with Chapter 8. No special color is associated with this quadrant.
4.2 Assignment of Ratings. 4.2.1 The hazard evaluation required to determine the cor- rect numerical ratings for a specific material shall be per- formed by persons who are technically competent and experi- enced in the interpretation of the hazard criteria set forth in this standard. 4.2.2* Assignment of ratings shall be based on factors that encompass a knowledge of the inherent hazards of the ma- terial, including the extent of change in behavior to be an- ticipated under conditions of exposure to fire or fire con- trol procedures. 4.2.3 The system shall be based on relative rather than abso- lute values, requiring considerable judgment be exercised. Based upon professional judgment, the hazard rat- ing shall be permitted to be either increased or decreased to more accurately assess the likely degree of hazard that will be encountered.* It shall be anticipated that different physical forms of the material or conditions of storage and use could result in different ratings being assigned to the same material.
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