A novel and complete methodology is presented to deduce a newly discovered (third type) steady state pyrolysis (ablation) rate on a composite material consisting of a pyrolysing material with inert backing when the composite material is exposed to a constant heat flux. The other two commonly known steady pyrolysis rates manifest when the pyrolysing material is thermally thick and when the temperature throughout the pyrolysing material is equal to its pyrolysis temperature. The value of the third type steady pyrolysis rate is accurately determined in terms of the thermal and pyrolysis properties of the composite material together with a delineation of the conditions under which it can be attained. The results are significant both for designing heat shields and for investigating the pyrolysis properties of materials in cone calorimeter type apparatus. (C) 2007 Elsevier Ltd. All rights reserved.