USDOT Hazardous Materials Regulations (HMR) identify nine different hazard classes. One of them - perhaps the most common - is the Class 3 Flammable and Combustible Liquid. But just what is a Class 3? And is it possible for a Flammable Liquid to be re-classed to a Combustible Liquid? This video summarizes complex HMR to bring the answer right to you.