PKP is the dry
potassium bicarbonate powder found in many fire extinguishers. PKP is so effective at smothering fires because of the way it decomposes when exposed to
heat. The main use for PKP is to stop oil and gas fires, but normal household extinguishers utilizing PKP are becoming more and more popular. The chemical is relatively cheap and very effective. Its
HMIS rating stands at 1 for Health, 0 for Fire and 0 for Reactivity.
Potassium bicarbonate's empirical chemical formula is KHCO3. The bicarbonate polyatomic ion, HCO3-, is what makes PKP so valuable. PKP decomposes at 350 degrees Fahrenheit, and does not melt. The byproducts of this decomposition are K2CO3, carbon dioxide (CO2), and water (H2O). Carbon dioxide and water are both commonly used against fire, and having a dry compound that breaks down into those two is a godsend. The third byproduct can be extremely abrasive, so PKP is not the chemical of choice for use on electrical fires. It's probably not the best thing for your health to hang around clouds of PKP that form when it's released.
Given the circumstances in which it is used, PKP alone hardly ever puts out a fire. Since it's utilized primarily to help put out oil and gas fires, the source of the fuel must be shut down to prevent flames from starting again. But when it's used in a simple household fire extinguisher, that is not of great concern.