National Fire Rating System

drawing of the NFPA sign The signs with four colored diamonds seen on buildings and trucks are a part of a system established by the National Fire Protection Association to warn fire and other emergency response personnel of potential dangers from hazardous materials within a building or vehicle. The numbers and symbols within the diamonds have the following meanings; complete descriptions are found in the Association's Recommendations for Identification of Fire Hazards of Materials:

Flammability (red, top square)

4	Very flammable gases or very volatile flammable liquids.
3	Can be ignited at all normal temperatures.
2	Ignites if moderately heated.
1	Ignites after considerable preheating.
0	Will not burn.

Health (blue, left square)

4	Can cause death or major injury despite medical treatment.
3	Can cause serious injury despite medical treatment.
2	Can cause injury. Requires prompt treatment.
1	Can cause irritation if not treated.
0	No hazard.

Reactivity (yellow, right square)

4	Readily detonates or explodes.
3	Can detonate or explode but requires strong initiating force or heating under confinement.
2	Normally unstable but will not detonate.
1	Normally stable. Unstable at high temperature and pressure. Reacts with water.
0	Normally stable. Not reactive with water.

Specific Hazard (white, bottom square)

OX	Oxidizing agent.
W	Water reactive.
	Radioactive.
	Biohazard.