Substance liable to self heat and spontaneously ignite under storage or transportation conditions can be a serious fire hazard in several industries. In order to estimate if, under specific storage conditions, a substance will dangerously self heat up to ignition, it is necessary to have knowledge of several thermochemical properties of the substance itself. Among this properties, one of the most relevant is the overall activation energy of the exothermic reactions that are responsible of the internal heat generation. In this short communication it will be discussed the possibility to retrieve the value of the overall activation energy from oven heating experiments conducted at temperature below the critical temperature of the sample, taking as an example a set of experimental data retrieved for commercially available charcoal briquettes. (C) 2014 Elsevier Ltd. All rights reserved.