Hi there,
I would like to ask a question, how does a dry powder fire extinguisher (KHCO3) work to extinguish a fire?
Thank you
P.S. I found out that the dry chemical part is made of KHO and the gas propelling the powder is CO2 thus KHCO3

Where did you get that info. I believe it is wrong. ABC extinguishers are almost always Ammonium Phosphate powders pressurized with Nitrogen. They form a blanket and exclude O2.