Radiation attenuation characteristics of pyrolysis volatiles from heated solid fuels, a neglected physical effect in radiant ignition process, are studied by Simulated experiment and mathematical models. Firstly, it is experimentally found the radiation attenuation of an incident heat flux when pine or Polymethyl Methacrylate (PMMA) is heated occurs before flaming ignition (6-14%), especially for the one in the experiment of the Cone Calorimeter style apparatus with a shorter test radiation distance (D < 100 mm). Then, a more reasonable parameter using Beer's law for determining the radiation absorptivity of pyrolysis volatiles of different fuels is presented. It is found the radiation absorptivity of pyrolysis volatiles of PMMA is actually larger than the one of pine and the ignition of PMMA more depends on the gas-phase heating by radiation absorption. Finally, the calculated results with the experimental radiation attenuation data illustrates that consideration of the radiation attenuation by pyrolysis volatiles in radiant ignition models is necessary. A constant radiation attenuation coefficient G = 0.1 is approximately accepted for the general calculation of radiant ignition model. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.