The slow combustion of ketene was investigated in the low-temperature range 280–350 °C. It differs from the reaction at higher temperatures chiefly by the presence of peroxides (mostly hydroperoxides) and the absence of methane. The main products: formaldehyde, carbon monoxide, water, and carbon dioxide are the same in both cases. A reaction scheme is proposed, which involves degenerate branching through the decomposition of methyl hydroperoxide: CH3OOH = CH3O• + •OH.