The increased use of alcohols in internal combustion engines has driven the attention to formaldehyde emissions. Yet the experimental database on formaldehyde flames is limited. The experimental structures of two formaldehyde flames have been investigated at low pressure (30 mbar) using a molecular beam sampling coupled with a mass spectrometer. The initial compositions are for the lean flame (phi = 0.22): 18% CH2O and 82% O-2, and for the stoichiometric one (phi = 1.09): 17.7% CH2O, 16.3% O-2 and 66.0% Ar. A kinetic model, previously elaborated, has been improved by building a complete submechanism taking into account the formation and consumption of species involved in the formaldehyde combustion. The improved mechanism contains 107 chemical species and 568 reactions in order to simulate these two formaldehyde flames accurately. The reliability of this kinetic model has also been tested in ethanol and acetaldehyde flames. This allows the extension of its validity range. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.