This work presents the results of an experimental and modelling investigation of the ignition of quiescent methane/air mixtures caused by radiation-heated large inert particles. The experimental data indicate that the explosion-delay time is inversely proportional to the radiative power flux. The delay time exhibits a minimum at a methane/air ratio near to stoichiometric. The mathematical model incorporates the basic principles of the thermal initiation mode of detonation phenomena. The experimental values of the explosion-delay time correlate with the predictions, hence lending weight to the proposed model. (c) 2005 Elsevier Ltd. All rights reserved.