What do they mean?
The National Fire Protection Association has developed a standard system for identifying chemical hazards. It consists of a diamond with four fields indicating hazards on a 1-4 scale for health, flammability and reactivity and a special field for unique hazards. You may encounter these symbols and numbers in the laboratory environment.
Health - Blue
- 4. Very short exposure could cause death or major residual injury.
- 3. Short exposure could cause serious temporary or moderate residual injury.
- 2. Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury.
- 1. Exposure would cause irritation with only minor residual injury).
- 0. Poses no health hazard, no precautions necessary.
Fire - Red
- 4. Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23°C (73°F).
- 3. Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point below 38°C (100°F) but above 23°C (73°F).
- 2. Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38°C (100°F) and 93°C (200°F).
- 1. Must be pre-heated before ignition can occur. Flash point over 93°C (200°F).
- 0. Will not burn.
Reactivity - Yellow
- 4. Readily capable of detonation or explosive decomposition at normal temperatures and pressures
- 3. Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked
- 2. Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water
- 1. Normally stable, but can become unstable at elevated temperatures and pressures
- 0. Normally stable, even under fire exposure conditions, and is not reactive with water
White - Special
*Note: W and OX are the only approved symbols in the NFPA 704 standard, however the above listed additional symbols are sometimes used in an unofficial manner.
- W - reacts with water in an unusual or dangerous manner
- OX or OXY - Oxidizer
- COR- Corrosive; strong acid or base
- ACID and ALK are more specific
- BIO - Biological hazard
- POI - Poisonous
- - is radioactive
- CRY or CRYO - Cryogenic