Class A Extinguishers are labeled with a number from 1 to 40.The number is an expression of the extinguisher’s fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
Class B Extinguishers are labeled with a number from 1 to 640.The number is an expression of the extinguishers fire-fighting effectiveness. The larger the number, the larger the fire the extinguisher can be expected to extinguish.
There is no numeric designation for an extinguisher’s effectiveness in fighting Class C, D, or K fires. The letters C, D, or K tell you only that the unit has been rated to combat energized electrical equipment, combustible metals, or cooking oil fires.