Fire extinguishers are divided into four categories and Fire Extinguisher Ratings are based on types of fire. While purchasing a extinguisher, I was ignorant about numerical ratings. The shop attendant explained to me that the fire extinguisher rating is a vital consideration since based on the ratings I could evaluate the extent of the fire fighting capacity of the extinguisher. He elaborated on classes A and B fires while classes C and D do not possess any numerical fire ratings. I came back quite astounded as to how much we have yet to learn about fire extinguishers.