Based on the analogy with the steady countercurrent reactor, a simplified theoretical solution is presented, which is applicable to adiabatic inert porous media combustors with reciprocating flow. The model consists of two ordinary differential equations that link all major controlling parameters, which allow for a good physical understanding of the process. The maximum temperatures in the burner predicted by the simplified model show the same trends as those in experimental results, but are generally higher, and the discrepancy between the experimental data and predications is less than 20%. By analyzing experimental and simulation results, a simplified theoretical solution for the temperature profile in the burner is further developed, which is expressed in terms of a piecewise linear function and the lean flammability limit is presented by a implicit expression. Results show that the lean flammability limit can be extended by using porous media of smaller pore size. The predicted lean flammability limit provides guidelines for the design of the combustor and some indications for further improving the combustor performances. (C) 2008 Elsevier Ltd. All rights reserved.