The minimum explosible concentration (MEC) and flame propagation behaviors of propane/L-leucine powder hybrid mixtures were experimentally investigated. The results of the experiment demonstrated that the MEC values decreased as the propane concentration increased. Additionally, the findings of the analysis proved that the flame propagation limitation in dust explosions increased with the increase in propane concentration. The results indicated two things. First, the flame speed of stoichiometric propane-air/L-leucine powder hybrid mixtures in the initial period of propagation was almost constant notwithstanding an increase in the L-leucine concentration. Second, the dimensionless flame speed was close to unity because the speed of the hybrid mixture was strongly affected by the propane-air premixed flame speed, although the flame speed increased with the increase in propane concentration. Further, it was found that the separate propagating flames of dust/gas hybrid mixtures had a considerable difference in flame speeds were observed. (C) 2020 Elsevier B.V. All rights reserved.