We show that the proportion of double Auger decay following creation of single 1s core holes in molecules containing C, N and O atoms is greater than usually assumed, amounting to about 10% of single Auger decay in many cases. It varies from molecule to molecule, where the size of the molecule have a positive correlation to the amount of double Auger decay. In neon, examined as a related benchmark, the proportion of double Auger decay is similar to that in methane, and is in the order of 5%.