The US Department of Transportation (DOT) classifies hazardous materials according to the risks that they pose. There are nine hazard classes:

• Class 1: Explosives
• Class 2: Gases
• Class 3: Flammable liquids
• Class 4: Flammable solids
• Class 5: Oxidizers/organic peroxides
• Class 6: Toxic and infectious substances
• Class 7: Radioactive material
• Class 8: Corrosives
• Class 9: Miscellaneous hazardous materials

Within class 6 are two divisions:

• Division 6.1- poisonous material
• Division 6.2- infectious substance

A division 6.2 infectious substance is defined as a material known or reasonably expected to contain a pathogen.

A pathogen is a microorganism or other agent (e.g., a prion) that can cause disease in humans or animals.

The regulations that govern packaging and shipping a class 9, miscellaneous hazardous material, may also need to be reviewed by those who package and ship laboratory specimens. Dry ice is a class 9 hazardous material and, if used, requires special packaging, and specific labeling and marking on the outer package.