Formaldehyde is a key species produced during oxidation of virtually all hydrocarbon and oxygenated fuels, and it is also a regulated hazardous air pollutant. An improved understanding of its formation and destruction chemistry is therefore vital to the study of many energy conversion processes. To this end, this work experimentally and numerically investigates the flame chemistry of formaldehyde (CH2O) at atmospheric pressure. The laminar burning rate of 1,3,5-trioxane/O2/N2 mixtures is measured in outwardly propagating spherical flames, where high concentrations of formaldehyde are generated early in the flame structure from decomposition of 1,3,5-trioxane. Though laminar burning rate predictions of several combustion kinetic models vary significantly, simulations agree that observables measured at the present experimental conditions are particularly sensitive to the competition between reactions HCO+O2=CO+HO2 and HCO(+M)=H+CO(+M). The present experimental measurements provide accurate data sensitized to these important HCO reactions, and are a valuable constraint for small molecule kinetic models.