We consider a conceptual isobaric combustion process that utilizes carefully controlled preheating to promote near-equilibrium combustion of hydrogen in air. Based on first and second law analyses, we demonstrate that this type of combustion could theoretically have higher retained thermodynamic availability than conventional combustion. While this specific combustion approach may not be practical, it may lead to new approaches for making hydrogen combustion a more efficient motive power source. Crown Copyright (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.