Dust dispersibility, the tendency of dust to form clouds that remain airborne, can be an important safety parameter in preventing dust explosion. One measure to moderate dust explosion hazards is adding solid inertants to combustible dust. In addition to being a solid inertant, noncombustible silica is sometimes used as an anti-caldng agent or fluidization enhancement additive in powder systems, affecting particle interactions in dust clouds. In this study, six types of combustible dust were admixed with micro- and nano-sized silica to study the effect on dispersibility and ignition hazard in a Godbert-Greenwald (G-G) furnace. Both micro- and nano-silica increased dispersion for some dust types, by changing contact geometry between combustible particles, and thereby decreasing inter-particle forces. Only for polyethylene did addition of 1% micro-silica cause increased dispersibility resulting in enhanced ignition hazard, with minimum ignition temperature (MIT) slightly decreasing 10 degrees C. No reduced MIT values were found with 1% nano-silica. (C) 2020 Elsevier B.V. All rights reserved.