Most manufacturers use labels or placards to identify flammable and combustible liquids in shipment. That identification method is different from the NFPA 704 system, which identifies the presence of hazardous materials — including flammable and combustible liquids — at fixed sites. Fixed sites can include factories, laboratories, and other facilities.
The diamond sign characterizes the NFPA 704 system. The diamond identifies the hazards of a material and the degree of severity of health, flammability, and instability hazards. Hazard severity is indicated by a numerical rating that ranges from zero (0), indicating a minimal hazard, to four (4), indicating a severe hazard.
The diamond distinguishes the hazards by spatial orientation and by color. The spatial arrangement of the hazards is health at 9 o'clock, flammability at 12 o'clock, and instability at 3 o'clock. The hazards use the following color coding: blue for health, red for flammability, and yellow for instability.