Hazardous materials receive NMFC code 1.1 through code 9, depending on the material. The National Motor Freight Traffic Association determines the NMFC classification codes for hazardous materials.
Codes 1.1 to 1.6 designate various types of explosives. Codes 2.1 to 2.3 label dangerous gases. Code 3 indicates a flammable liquid, while codes 4.1 to 4.3 indicate flammable solids and other combustible materials. Codes 5.1 to 5.2 refer to various oxidizers such as organic peroxide, and codes 6.1 to 6.2 indicate poisons and infectious substances. Code 7 designates radioactive materials, while code 8 is for corrosive materials such as acid. Code 9 indicates a material not included in any other category.