A standard 20 L sphere chamber was modified to be adapted for measuring the explosion parameters of hybrid mixtures of ethylene and polyethylene dust. The change rules of the lower flammability limits and explosion severity of the hybrid mixtures were analyzed systematically. The explosion severity of ethylene

polyethylene and their mixtures were compared with each other. The results show that the addition of ethylene induces an obvious decrease in the minimum explosion concentration of polyethylene dust. Mixtures of ethylene below its lower flammability limit and polyethylene dust below its minimum explosion concentration were still explosible. Adding ethylene to polyethylene dust cloud of different concentrations increases both the explosion pressure pex and the rate of explosion pressure rise (dp/dt)ex. But the increase range decreases with the increase of dust concentration. The maximum explosion pressure pmax and explosion index Kst of ethylene and polyethylene mixtures increase with the increase of ethylene concentration. While the maximum explosion pressure pmax and explosion index Kst of the hybrid mixtures of ethylene and polyethylene are higher under all ethylene concentrations than those of the pure polyethylene

but lower than those of the pure ethylene.