NFPA 704 Hazard Diamond Guide
What the NFPA hazard diamond is, how to read each colored section, where diamonds should be posted and how big they need to be.
Understanding the NFPA hazard diamond
The NFPA Hazard Diamond, part of the NFPA 704 standard, is a diamond-shaped symbol that provides emergency responders with a quick overview of a material's health, flammability, instability and special hazards.
Divided into four color-coded quadrants, it uses a 0-4 numerical rating system for the blue (health), red (flammability) and yellow (instability) sections, with 0 indicating no hazard and 4 indicating extreme danger. The white quadrant identifies special hazards, such as reactivity with water or corrosive properties, using symbols like "W" or "COR".
The diamond is a vital tool for emergency responders to quickly assess hazards and determine the appropriate safety precautions and protective gear needed when dealing with a hazardous substance or facility. It is part of a larger system designed to improve safety in buildings and facilities that store hazardous materials.
How to read an NFPA hazard diamond
Each colored section rates one kind of hazard from 0 to 4. The white section carries symbols instead of a number.
Blue: health
The blue section identifies a material’s health hazard.
- Normal material that poses no hazard.
- Slightly hazardous, can cause significant irritation.
- Hazardous, including temporary incapacitation or residual injury.
- Extreme danger, including serious or permanent injury.
- Deadly.
Red: flammability
The red section assesses a material’s flammability.
- Will not burn, even under typical fire conditions.
- Materials that must be preheated before ignition can occur, including materials that have a flash point above 200°F.
- Materials that must be moderately heated to ignite, including materials with a flash point below 200°F.
- Materials that can be ignited at ambient temperatures, with a flash point below 100°F.
- Materials which will vaporize at ambient temperatures and pressures, and will burn readily below 73°F.
Yellow: instability
The yellow section identifies a material’s instability and reactivity.
- Stable even in fire exposure conditions.
- Unstable at elevated temperatures or pressures.
- Violent chemical change at elevated temperatures or pressures.
- Explosive reactions in the presence of a strong initiating source, such as shock or heat.
- Capable of detonation or explosion at normal temperatures and pressures, react explosively with water.
White: special hazards
The white section details a material’s specific and special hazards. It differs from the other three because it can be blank if there are no special hazards. Three special notice symbols are included, along with several non-standard symbols that are widely recognized and may be required per local codes and standards.
Special symbols
Non-standard symbols
Location of NFPA hazard diamonds
General guidelines for where to post them.
- Visible in case of an emergency, where first responders are likely to enter.
- Numerous placards in numerous locations.
- At minimum: two exterior walls of the facility or building, each entryway to a room or area, or each primary means of access to an exterior storage area.
Viewing distance chart
Pick the diamond size by how far away it has to be read.
| Diamond size | Character height | Legible viewing distance |
|---|---|---|
| 3" x 3" | 1" | 1' to 40' |
| 6" x 6" | 2" | 41' to 85' |
| 9" x 9" | 3" | 86' to 135' |
| 11" x 11" | 4" | 136' to 150' |
| 15" x 15" | 6" | 151' to 200' |
| 20" x 20" | 8" | 201' to 300' |
| 24" x 24" | 10" | 301' to 400' |
Shop NFPA signs and tags
This page summarizes the NFPA 704 rating system for reference. Consult the current NFPA 704 standard and your local codes for the complete requirements.
Not sure what ratings to use?
Check the Safety Data Sheet for the material, or send us your list and we'll quote the signs.