The red (upper) quadrant of the NFPA 704 symbol. The values are: 4 - Danger. Flammable gas or extremely flammable liquid. 3 - Warning. Flammable liquid, flash point below 1000F (380C). 2 -Caution. Combustible liquid, flash point of 1000 to 2000F (380 to 930C). 1 - Combustible if heated. 0 - Not combustible