CO and CO2 evolution was measured in a cerium and in a ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction. These gases were stripped from the reaction mixture by a N-2 carrier gas, mixed with H-2, converted to methane on a Ni catalyst, and then measured by a flame ionization detector (FID). CO could be detected separately by absorbing CO2 on a soda lime column. In separate experiments it was proven that CO is produced in a reaction of BrO2 center dot radicals with bromomalonic acid (BrMA). To this end BrO2 center dot radicals were generated in two different ways: (i) in the reaction HBrO2 + HBrO3 <-> 2 BrO2 center dot + H2O and (ii) by reducing HBrO3 to BrO2 center dot by Fe2+. It was found that (OH)-O-center dot radicals produced by Fenton's reagent can also generate CO from BrMA. We propose that CO can be formed when an inorganic radical (like BrO2 center dot or (OH)-O-center dot) reacts with the enol form of BrMA producing an acyl radical which decarbonylates in the next step. Malonic acid (MA)-BrMA mixtures were prepared by a new method modifying Zaikin and Zhabotinsky's original recipe to minimize the production of dibromomalonic acid (Br(2)MA).