Dust of hops, lemon balm leafs, sennae fruits, nettle roots and valerian roots (particle size below 71 pm, concns. 125-1250 g/m(3)) were studied for explosion hazards. The max. explosion pressure and the max. rates of pressure rise of dust clouds were detd. by std. methods. The pressure rise rate varied from 193 bar/s (sennae fruits) up to 285 bar/s (valerian roots) at dust concn. 1000 g/m(3).