Just as there is a right tool for every job, there is a right extinguisher for every fire. The class of an extinguisher, identified on its nameplate, corresponds to the class or classes of fire the extinguisher controls. On most construction jobs, we are concerned with Class A, B and C fires. Consequently, the best extinguisher to have on a job is a multi-purpose Class ABC extinguisher, which contains a dry, powdered chemical under pressure. The following describes the classes of fire and the kind of extinguisher that can be used on each.
CLASS A FIRES
For ordinary combustibles, such as wood, paper, trash and other material that has glowing embers when it burns, use a Class A or Class ABC extinguisher. Always remember that a Class A extinguisher contains water and should be used only on a Class A fire. Used on gasoline, it can spread the fire; used on electrical fires, it can cause you to be electrocuted.
CLASS B FIRES
These are fires involving flammable liquids and gases, such things as gasoline, solvents, paint thinners, grease, LPG, and acetylene. Use Class B or Class ABC extinguishers.