Chemical Hazard Symbols and Their Meanings

The red symbol represents flammability.

The National Fire Protection Agency (NFPA) is a private non-profit organization. The NFPA is the best source for data, advice and background information on fire protection, problems and prevention. The NFPA has a standard chemical/ fire hazard symbol that is widely used. This symbol is a diamond with four different colored sections within it; Blue, red, yellow and white. Each of these area represents a different kind of hazard the specific chemical might pose.

Blue

The blue diamond within the NFPA diamond represents whatever health hazards the chemical poses. The health hazard is rated on a scale from 0 to 4. Each number, in ascending order, denotes an increased risk. The number 0 represents that there is no hazard other than that which ordinary combustible materials pose. The number 4 represents that very short exposure to this chemical could cause death or a serious residual injury, even if immediate medical attention is given.

Red

The red diamond on the chemical hazard symbol represents the flammability of the chemical. The flammability rating is on a scale of 0 to 4, increasing in danger as the numbers ascend. A 0 in flammability denotes that this chemical will not burn. A 2 in flammability lets the user know that the chemical requires moderate heating or exposure to relatively high temperature before it will ignite. A 4 in flammability is a warning that the chemical will rapidly or completely vaporize in the air at normal temperatures, or that it will easily disperse in the air and that it will burn readily.

Yellow

The yellow symbol of the NFPA's chemical hazard label represented "reactivity" prior to 1996, but it was changed to "instability" to avoid confusion between the chemical reactivity of the material and a reactive hazard. The instability scale ranges from 0 to 4. A 0 in instability represents that the chemical is normally stable and is not reactive with water. A 4 on the instability chart represents that the chemical is either readily able to detonate or react at normal temperatures and pressures.

White

The white diamond of the NFPA chemical hazard label represents any special hazard that the chemical represents. There are only three acceptable symbols that the NFPA puts in to this area. An "OX" denotes that this chemical is an oxidizer, which is a chemical that can increase the rate of combustion tremendously. An "SA" represents that this chemical is a simple asphyxiant. There are only six acceptable gases to use "SA" with: Nitrogen, helium, neon, argon, krypton and xenon. The final acceptable symbol is a W with a bar horizontally through it. This symbol represents that this chemical has an unusual reaction with water. Usually this means that it can be dangerous to fight a fire involving this material with water.

Other Symbols

The NFPA does allow a few miscellaneous symbols directly below their diamond label. The first is "ACID," meaning that the chemical within is an acid, which is a corrosive material with a pH below 7.0. Secondly, "ALK" is used to denote an alkaline or base material, that is caustic and has a pH above 7.0. Thirdly, "COR" is used to represent a generally corrosive material, which could be either base or acidic. Finally there are four pictorial representations; the skull and crossbones, a symbol of a vial dripping on to a hand, the universal radiation symbol, and a depiction of an explosion. These four symbols are uncommonly used and are only allowed below the NFPA diamond.

References

• Interactive Learning Paradigms Incorporated: The MSDS Hyperglossary