Measurements of the quenching rate coefficients for hydrogen atoms in the 3s 2S and 3d 2D states and of oxygen atoms in the 3p 3P state by rare gases and several combustion-relevant collision partners are presented. The excited atomic states are prepared by two-photon laser excitation. Quenching cross sections for most collision partners are found to be larger than classical collision cross sections; H atoms are mostly quenched faster than O atoms. For the quenching of H and O atoms by the rare gases, the rate coefficients increase significantly with the mass of the rare gas atom.