National Fire Protection Association Diamonds – What Do They Mean? (Guest Post)

NFPA Diamonds – What Do They Mean?

The National Fire Protection Association (NFPA) is an organization that supports research, training, and education on the topics of fire-related hazards. In promoting their goal of reducing fire and other hazard-related hardships, they have created standards and codes to alert of and prevent hazardous situations. 

The NFPA specified a system to identify hazards in section 704 of the National Fire Code. Referred to as NFPA 704, the code developed a hazard identification system that is arranged in the shape of a diamond and uses colors, numbers, and symbols to identify the potentially hazardous materials held within a container or structure. 

The NFPA 704 signs are usually referred to as NFPA diamonds, 704 diamonds, or NFPA placards. The colors used on the signs are blue, red, yellow, and white, each for a type of chemical hazard. A number ranging from 0 to 4 or symbol is labeled within each colored area to alert of the severity of each hazard. 

The Blue Diamond – Health

The blue section of NFPA diamonds identify health hazards associated with each material. Health hazards can range from skin irritants to carcinogens, and are numbered based on their potential damage to a person’s health when the material is exposed to fire conditions. 

With each progressing level of hazard, emergency response personnel would adjust their level of personal protection. This would range from standard firefighting gear like helmets and face shields to specialized protective equipment such as vapor-protective suits. 

A rating of zero denotes that there is no additional hazard beyond that of a normal combustible material such as paper and wood. Examples of these chemicals would be denatured alcohol and peanut oil. 

Materials rated as one can cause irritation but only slightly lingering injury. Materials with this rating include acetone, turpentine, and methane. 

If exposure to chemicals rated as two is not habitual or chronic, but still extraordinary, temporary incapacitation or lasting injury may occur. Ammonia gas, benzene, chloroform, and styrene carry this level of hazard. 

More serious is the rating of three, which includes hydrochloric acid, sulfur dioxide, and mustard oil. Chemicals such as these may cause serious lasting injury, even during a short period of exposure. 

NFPA diamonds for materials that pose the greatest health risks have blue areas marked with four. These materials can cause death or major residual injury with the shortest exposure times. These hazardous materials include sarin, hydrogen cyanide, and chlorine. 

The Red Diamond – Flammability

NFPA diamonds’ red section alerts and identifies flammable hazards. The same scale of zero to four is used. Materials with a zero rating typically will not burn. Even if materials have a high rating as a health hazard, this does not mean that it is necessarily a high risk to combust. Chlorine, with the health rating of four, has a zero rating for flammability. 

Materials that need to be pre-heated before ignition can start commonly include oils, such as whale oil and corn oil, along with many types of wax. These materials are rated in level one on NFPA diamonds. 

Materials that will only combust when exposed to high temperatures or moderate heat have the rating of two. Camphor, diesel fuel, and pine tar are included in this rating. 

Flammability rating three includes materials that can combust under almost all ambient temperatures. In workplaces, these would also be known as open flame hazards, and include gasoline and crude petroleum. 

The most flammable materials are rated the highest at four. Propane, hydrogen gas, and methane are examples of materials that will quickly or completely vaporize at normal temperatures and pressures, or will disperse in the air and combust. 

The Yellow Diamond – Reactivity

Chemical reactivity on NFPA diamonds is measured in the yellow section. Reactivity refers to a material’s tendency to interact with other materials and the rate of the reaction. 

Corn oil, chlorine, and methane, all with varying ratings for health and flammability hazards, share a zero reactivity rating. These materials are normally stable, even under fire conditions. 

Materials that are also normally stable, but may become unstable at higher pressures and temperatures, are rated at one on NFPA diamonds. Lye, despite its high health hazard rating, is rated at this level. 

Chemicals that react violently and even becoming explosive with water, or at elevated temperatures and pressures, have a NFPA diamond reactivity rating of two. Potassium and lithium are two elements that carry this rating. 

Materials that react explosively with water, or are able to explode with a strong source of combustion, such as gaseous fluorine, have a level three rating. 

The most explosive materials, capable of detonation at normal pressures and temperatures, such as trinitrotoluene (TNT), are the most reactive, and NFPA diamonds have a four rating for these. 

The White Diamond – Special Notices

There are symbols in NFPA diamonds that alert responders to materials that can pose additional or increased hazard and require special precautions. Two symbols are included in the 1990 edition of the NFPA 704 standard.  They are: “W” and “OX.” 

W” refers to materials that react unusually with water, such as with calcium. Calcium is used in a variety of processes, and when exposed to water a reaction creates hydrogen gas, which is extremely flammable. 

“OX” symbolizes oxidizing materials on NFPA diamonds. Flammable materials need oxygen to complete the chemical reaction and burn. Oxidizing materials allow chemicals to burn without oxygen. A chemical as common as hydrogen peroxide, found in medicine cabinets to clean wounds, is a strong oxidizer, and could keep a fire burning through this type of reaction. 

By understanding what the sections of NFPA diamonds alert responders to, and that the numbers correspond with severity levels, you can avoid unnecessary risks in the workplace around potentially hazardous materials. This helps increase safety in your workplace and reinforces the reason why the NFPA created the 704 standard and the NFPA diamond signs.


About the Author: Stephen Luke is a writer for, a leading supplier of chemical safety signs, traffic signs, parking signs, and more.