The explosion behaviour of heterogeneous/homogeneous fuel-air (hybrid) mixtures is here analysed and compared to the explosion features of heterogeneous fuel-air and homogeneous fuel air mixtures separately. Experiments are performed to measure the pressure history, deflagration index and flammability limits of nicotinic acid/acetone-air mixtures in a standard 20 L Siwek bomb adapted to vapour-air mixtures. Literature data are also used for comparison. The explosion tests performed on gas-air mixtures in the same conditions as explosion tests of dust-air mixtures, show that the increase in explosion severity of dust/gas air mixtures has to be addressed to the role of initial level of turbulence prior to ignition. At a fixed value of the equivalence ratio, by substituting the dust to the flammable gas in a dust/gas-air mixture the explosion severity decreases. Furthermore, the most severe conditions of dust-gas/air mixtures is found during explosion of gas-air mixture at stoichiometric concentration. (C) 2011 Elsevier Ltd. All rights reserved.