An extended simplified model, applicable to every cycle period, for the simulation of the behaviour of an adiabatic reverse-how reactor for the treatment of waste gases is presented and compared to the complete model. This model is based on the analogy with the steady countercurrent reactor and consists of simple equations that relate the main input and dimensional parameters of the reactor. Such a model permits the setting up the guidelines for the design of the reactor and to obtain some indications for its control system, allowing the prediction of the limiting operating conditions for autothermal operation.