There are basically five different types or classes of fire extinguishers, each of which extinguishes specific types of fire. Newer fire extinguishers use a picture/labeling system to designate which types of fires they are to be used on. Older fire extinguishers are labeled with colored geometrical shapes with letter designations. Both of these types of labels are shown below with the description of the different classes of extinguishers.
Additionally, Class A and Class B fire extinguishers have a numerical rating which is based on tests conducted by Underwriter´s Laboratories that are designed to determine the extinguishing potential for each size and type of extinguisher.