Amerex 2-1/2 Lb. ABC Fire Extinguisher with Vehicle Bracket. ABC or Multi-Purpose extinguishers utilize a specially fluidized and siliconized mono ammonium phosphate dry chemical. It chemically insulates Class A fires by melting at approximately 350°F and coats surface to which it is applied. It smothers and breaks the chain reaction of Class B fires and will not conduct electricity back to the operator.