The NFPA diamond is one of the most iconic safety symbols in many different industries. Anywhere that works with potentially dangerous chemicals or materials will have seen this diamond. Even those who don’t work in these types of industries will likely have seen them on the backs of semi-trucks that are transporting dangerous solutions. The colors that are used in the NFPA diamond have a specific meaning and can make it easier for people to quickly identify what type of hazard is present for the chemicals that are being labeled.
Red NFPA Diamond
The top section of the NFPA diamond is going to be red. The more flammable the substance is, the higher the number that is in the diamond will be with a zero being not flammable at all, and 4 being the highest level of flammability.
Blue NFPA Diamond
On the left side of the NFPA diamond when looking at it will be the color blue. This is used to indicate that the chemical being labeled has some type of health hazard. If it has a zero in the blue diamond then there is no health hazards at all. As the number goes up to four the severity of the hazard continues to escalate.
Yellow NFPA Diamond
On the right side of the diamond when looking at it you will see a yellow diamond. This is used to indicate the instability of a chemical that is being labeled. This indicates that the chemicals may be extremely unstable if they have a 4 and are completely stable when there is a zero.
White NFPA Diamond
At the bottom of the NFPA diamond you will find a white area, which is used for special hazards. Rather than using numbers in this section you will see a letter or symbol. The most common of these is a W, which is used to indicate that the chemical has an unusual reaction when exposed to water. This is critical information for firefighters should they be responding to an emergency. Another common option in this section is OX, which signals those who see it that the substance is an oxidizer.
Similar Questions
Additional Resources
The hazard identification signal is a color-coded array of four numbers or letters arranged in a diamond shape.
The National Fire Protection Association (NFPA) specifies a system for identifying the hazards associated with materials.
About the Numbering Scale
- 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 - white- shows special precautions - either water reactive or an oxidizing agent.
Red: Flammability Hazard
- 4 – Materials with a flashpoint below 73°F and a boiling point above 100°F - 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. Example: propane gas.
- 3 – Materials with a flashpoint below 73°F and a boiling point greater than or equal to100°F, or a flashpoint above 73°F and less than 100°F - Liquids and solids that can be ignited under almost all ambient temperature conditions. Example: gasoline.
- 2 – Materials with a flashpoint above 100°F, but not exceeding 200°F - must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Example, diesel fuel oil.
- 1 – Materials with a flashpoint above 200°F - must be pre-heated to burn. Example: corn oil.
- 0 – Materials which normally won't burn.
Blue: Health Hazard
- 4 – Materials with an oral LD50 of less than or equal to 5 mg/kg - Material that on very short exposure could cause death or major residual injury. Example: hydrogen cyanide.
- 3 – Materials with an oral LD50 above 5, but less than 50 mg/kg - Material that on short exposure could cause serious temporary or residual injury. Example: chlorine gas.
- 2 – Materials with an oral LD50 above 50, but less than 500 mg/kg - Material that on intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. Example: ammonia gas.
- 1 – Materials with an oral LD50 above 500, but less than 2000 mg/kg - Material that on exposure would cause irritation but only minor residual injury. Example: turpentine.
- 0 – Materials with an oral LD50 above 2000 mg/kg - Material that on exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. Example: peanut oil.
Yellow: Reactivity Hazard
- 4 – Material is capable of explosion or detonation at normal temperature and pressure. Example: trinitrotoluene (TNT).
- 3 – Material is capable of explosion, but requires a strong initiating source, or the material reacts explosively with water. Example: fluorine gas.
- 2 – Material undergoes violent chemical changes at elevated temperature and pressure or which reacts violently with water or which may form explosive mixtures with water. Example: calcium metal.
- 1 – Normally stable, but can become unstable at elevated temperatures and pressures. Example: phosphorus (red or white).
- 0 – Normally stable - Material that in itself is normally stable, even under fire exposure conditions, and is not reactive with water. Example, liquid nitrogen.
White: Special Precautions
- W – Material shows unusual reactivity with water (i.e. don't put water on it). Example: magnesium metal.
- OX – Material possesses oxidizing properties.