The aim of this work is to demonstrate the particular aspects of the explosion of hybrid mixtures with respect to either vapour or dust explosions. This work is focused on pharmaceutical products from excipients to active drug substances and their associated solvents. Experiments with an explosion sphere has been used to determined the influence of dusts and vapours concentrations on the severity of explosions (maximum pressure P x and maximum rate of pressure rise (dP/dt)(max)). Results clearly show that the explosion behaviour of such hybrid mixtures reveals significant differences with respect to either vapour or dust explosions; especially a promotion effect on the combustion kinetics and on the rate of pressure rise for poor mixtures. The influences of the introduction of small amount of vapour on the minimum explosible dust concentration (MEC) and of dust addition on the lower explosion limit (LEL) are noteworthy. (C) 2008 Elsevier B.V. All rights reserved.