The diamond shaped diagram gives, at a glance, a general idea of the inherent hazards and the order of severity of these hazards under emergency conditions such as spills, leaks, and fires. The diagram identifies the "Health," "Flammability," and "Reactivity" hazards of materials and indicates the order of severity of each hazard by the use of numerical grading from four (4), indicating severe hazard or extreme danger, to blank, indicating no required warning. In the diamond shaped diagram, the "Health" hazard is identified at the left with a blue background, "Flammability" at the top with a red background, and "Reactivity" at the right with a yellow background. The bottom space is used to identify special hazards important to emergency response personnel and has a white background. Additional special hazards are listed in rectangular white boxes below the placard. For more information about the NFPA, visit


4 - Extreme

Materials which, on very short exposure, could cause death or major residual injury even though prompt medical treatment was given. Materials which will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature, or which are readily dispersed in air. Will burn readily. Materials which are readily capable of detonation or of explosive decomposition at normal temperatures and pressure.
3 - Severe

Materials which, on short exposure, could cause serious injury even though prompt medical treatment was given. Liquids and solids that can be ignited under almost all ambient temperature conditions. Materials which are capable of detonation or of explosive reaction but require a strong initiating source or that react explosively with water.
2 - Moderate

Materials which, on intense or continued exposure, could cause serious injury even if medical treatment is given.

Flash Point > 37.8 oC but < 93.3 oC.
Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur.

Materials which are normally unstable and readily undergo violent chemical change but do not detonate. Materials which may react violently with water or form potentially explosive mixtures with water.
1 - Slight

Materials which could cause possible injury, but are only slightly hazardous.

Flash Point > 93.3 °C.
Materials that must be preheated before ignition can occur.

Materials which are normally stable, can become unstable at elevated temperatures, or may react with water with some release of energy, but not violently.
0 - Minimal Materials are non-hazardous. Materials will not burn. Materials are not reactive.


U.S. Hotlines

Chemical Transportation Emergency Center (ChemTel)
National Institute of Occupational Safety & Health (NIOSH)
National Response Center
Poison Control Center
Substance Identification