NFPA 704 Marking System

NFPA 704 Marking System

NFPA Diamond

The National Fire Protection Agency (NFPA), in section 704 of the National Fire Code, specifies a system for identifying the hazards associated with materials. Information contained on this and linked pages comes directly from the 1990 edition of NFPA 704. Although the system was developed primarily with the needs of fire protection agencies in mind, it is of value to anyone who needs to handle potentially hazardous material.

Blue | Red | Yellow | White

The NFPA 704 Standard System for the Identification of the Hazards of Materials for Emergency Response, was developed as a manual by the Sectional Committee on Classification, Labeling and Properties of Flammable Liquids of the NFPA Committee on Flammable Liquids starting in 1952. Its first adoption as a guide occurred in 1961, with regular revisions being adopted through 1987. In 1990 it became an NFPA standard, and extensive quantitative health hazard rating criteria were introduced. The purpose of the standard, as originally conceived, is to safeguard the lives of those individuals who respond to emergencies occuring in an industrial plant or storage location, or other location where relatively large quantities of chemicals are used, and where the hazards of materials are not readily apparent.

The hazard identification signal is a color-coded array of four numbers or letters arranged in a diamond shape. An example is shown to the right. You will see hazard diamonds like this on trucks, storage tanks, bottles of chemicals, and in various other places around campus and around town.

The blue, red, and yellow fields (health, flammability, and reactivity) all use a numbering scale ranging from 0 to 4. A value of zero means that the material poses essentially no hazard; a rating of four indicates extreme danger. The fourth value (associated with white) tends to be more variable, both in meaning and in what letters or numbers are written there.

Select one of the four diamonds to the right to get more information.

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NFPA HEALTH 0 Material which on exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. Example:
peanut oil
1 Material which on exposure would cause irritation but only minor residual injury even if no treatment is given. Example:
2 Material that on intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. Example:
ammonia gas
3 Material that on short exposure could cause serious temporary or residual injury. Example:
chlorine gas
4 Material that on very short exposure could cause death or major residual injury. Example:
hydrogen cyanide

NFPA FLAMMABILITY 0 Material will not burn. Example:
1 Material must be pre-heated before ignition can occur.
Flash Point At or Above 200oF (93.4oC)
corn oil
2 Material must be moderately heated or exposed to relatively high ambient temperature before ignition can occur.
Flash Point At or Above 100oF (37.8oC) - Below 200oF (93.4oC)
diesel fuel oil
3 Liquids and solids that can be ignited under almost all ambient temperature conditions.
Flash Point At or Above 73oF (22.8oC) - Below 100oF (37.8oC)
Boiling Point At or Above 100oF (37.8oC)
4 Materials that will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature, or that are readily dispersed in air and that will burn readily.
Flash Point Below 73oF (22.8oC)
Boiling Point Below 100oF (37.8oC)
propane gas

NFPA REACTIVITY 0 Material that in itself is normally stable, even under fire exposure conditions, and is not reactive with water. Example:
liquid nitrogen
1 Material that in itself is normally stable, but which can become unstable at elevated temperatures and pressures. Example:
phosphorus (red or white)
2 Material that readily undergoes violent chemical change at elevated temperatures and pressures or which reacts violently with water or which may form explosive mixtures with water. Example:
calcium metal
3 Material that in itself is capable of detonation or explosive decomposition or reaction but requires a strong initiating source or which must be heated under confinement before initiation or which reacts explosively with water. Example:
fluorine gas
4 Material that in itself is readily capable of detonation or of explosive decomposition or reaction at normal temperatures and pressures. Example:
trinitrotoluene (TNT)

The fourth, white, field of the hazard signal can have variable content, depending on who prepared the signal. The 1990 edition of the National Fire Codes (section 704, chapter 5) specifies only "TWO" NFPA 704 approved symbols. Additional symbols are commonly included. The field may also be left blank if no special hazards are present.
NFPA SPECIAL NOTES OX Material possesses oxidizing properties. A chemical which can greatly increase the rate of combustion/fire. Example:
ammonium nitrate
(fertilizer used in
Oklahoma City bomb)
NFPA SPECIAL: NO WATER Unusual reactivity with water. This indicates a potential hazard using water to fight a fire involving this material.(i.e. don't put water on it) Example:
magnesium metal

Other symbols, abbreviations, and words that some organizations use in the white Special Hazards section are shown below. These uses are not compliant with NFPA 704, but we present them here in case you see them on an MSDS or container label:
NFPA SPECIAL NOTES ACID This indicates that the material is an acid, a corrosive material that has a pH lower than 7.0
ALK This denotes an alkaline material, also called a base. These caustic materials have a pH greater than 7.0
COR This denotes a material that is corrosive (it could be either an acid or a base).
NFPA SPECIAL: RADIOACTIVE The international symbol for radioactivity is used to denote radioactive hazards; radioactive materials are extremely hazardous when inhaled.
NFPA SPECIAL: CORROSIVE This is a another symbol used for corrosive.
NFPA SPECIAL: POISION The skull and crossbones is used to denote a poison or highly toxic material.
NFPA SPECIAL: EXPLOSIVE Indicates an explosive material. This symbol is somewhat redundant because explosives are easily recognized by their Instability Rating.

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