Hot surface ignition is relevant in the context of industrial safety. In the present work, two-dimensional simulations with detailed chemistry, and study of the reaction pathways of the buoyancy-driven flow and ignition of a stoichiometric hydrogen-air mixture by a rapidly heated surface (glowplug) are reported. Experimentally, ignition is observed to occur regularly at the top of the glowplug; numerical results for hydrogen-air reproduce this trend, and shed light on this behavior. The simulations show the importance of flow separation in creating zones where convective losses are minimized and heat diffusion is maximized, resulting in the critical conditions for ignition to take place. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.