Regular dry chemical fire extinguishers contain a siliconized sodium bicarbonate based dry chemical with free flowing and non-caking additives. Economical Class B & C protection with lower initial cost and recharging. This chemical smothers fires in flammable liquids & pressurized gases and is electrically nonconductive.Multipurpose dry chemical or ABC fire extinguishers contain a specially fluidized and siliconized mono ammonium phosphate chemical. It chemically insulates Class A fires by melting at approximately 350°F, coating the surface to which it is applied. It smothers & breaks the chain reaction of Class B fires and will not conduct electricity.