All the recently occurred accidents involving powdered materials demonstrate that dust explosion is up to now an open problem. To mitigate the effects of this phenomenon on people, environment and equipment, it is important to understand the characteristics of the potentially explosive material which can affect the violence of a dust explosion. The deflagration index is the most relevant recognized parameter able to measure the severity of such a phenomenon. Among all the critical issues affecting the use of this parameter for industrial safety, the particle size distribution of the tested powder plays a relevant role. In this paper, a simple but reliable mathematical model has been proposed to describe the effect of the mean particle diameter on the dust explosibility. model predictions have been compared with both literature and new experimental data in order to validate the general proposed approach. (C) 2017 Elsevier Ltd. All rights reserved.