NFPA 704: Understanding Hazard Warning Labels
You can help prevent illness and injury by reading the warning label for each hazardous substance you use. If you have any questions after reading the warning label, check the SDS. The SDS is a detailed source of information for the hazardous substance you are using. The image is an example of a National Fire Protection Association (NFPA) label you might find on a container.
NFPA 704 warning labels
You may see a warning label on a container or box of containers, such as a case of chemical jugs. These labels provide the most important information you need to know about the substance you are handling.
The number system is based on the NFPA 704 rating:
Hazard ratings range from 0 to 4, with 4 being the most hazardous. These are used for 3 categories: health (blue), flammability (red), and instability (yellow). For example, if the substance has a low risk for flammability, a “1” may appear in the Flammability section.
The Special Hazard category shows other important hazards to be aware of. These include OX (oxidizers), W (water reactives), and SA (simple asphyxiants).