This paper describes a semi-empirical method to predict the maximum pressure for fuel/air deflagrations over the entire flammable range. The method is based on availability, which is a thermodynamic concept representing the maximum mechanical energy extractable from a given mass of material. In total eight fuel/air systems were considered - the deviation between the predicted and experimental maximum pressure is from -20 psia to +15 psia. This is a significant improvement over ideal gas or equilibrium prediction methods. (C) 2000 Elsevier Science Ltd. All rights reserved.