Amerex B479T, 5lb Purple K Chemical Class B C Fire Extinguisher. Purple K Chemical Class B:C. For use on Class B (Flammable liquid) spills or Fires involving live electrical equipment (Class C). All metal valve construction, Brass Valve. Description Amerex 5lb Purple K with aluminum valve fire extinguishers contain specially fluidized and siliconized potassium bicarbonate dry chemical which is particularly effective on Class B flammable liquids and pressurized gases.Purple K has been the choice of oil, gas, chemical and utilities industries as the preferred fire fighting agent. Any product you return must be in the same condition you received it and in the original packaging. We usually respond within 24 hours on weekdays. Thank you for shopping at our store.