AbstractThe high‐temperature oxidation of formaldehyde in the presence of carbon monoxide was investigated to determine the rate constant of the reaction HO2+ CO  CO2+ OH (10). In the temperature range of 878–952°K from the initial parts of the kinetic curves of the HO2radicals and CO2accumulation at small extents of the reaction, when the quantity of the reacted formaldehyde does not exceed 10%, it was determined that the rate constantk10is\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{10} = (1.7 \pm 0.5) \times 10^{ - 10} \exp [ - (23,000 \pm 3000/RT)]\,{\rm cm}^{\rm 3} /{\rm molec}{\rm.sec} $$\end{document}A computer program was used to solve the system of differential equations which correspond to the high‐temperature oxidation of formaldehyde in the presence of carbon monoxide. The computation confirmed the experimental results. Also discussed are existing experimental data related to the reaction of HO