How do you read the fire extinguisher ratings?

Fire extinguishers are classified by fire type. The A, B and C rating system defines the kinds of burning materials each fire extinguisher is designed to fight. The numbers in front of the A, B, or C indicate the rating for size of the fire the unit can extinguish. Using the wrong type of fire extinguisher can do more harm than good. Make sure you understand which fire extinguisher to use on each class of fire.  
Class A rating: The agent/powder is suitable for fighting small fires involving wood, paper, cloth, rubber, and some plastics.  
Class B rating: The agent/powder is suitable for fighting small fires involving grease, oil, gasoline, kerosene, and other flammable liquids.  
Class C rating: The agent/powder is suitable for fighting small fires in “live” electrical equipment.