Hotspots (overheated contact components) generated by machinery malfunction serve as an effective ignition source, contributing to almost 12% of dust explosion accidents worldwide, and pose a significant hazard for metallic powder manufacturing. The minimum ignition temperature of hotspots (MITH) of micro and nano Ti powder was only 586 degrees C and 225 degrees C, respectively. Admixing of TiO2 powder decreased the ignition hazard of micro Ti powder exposed to hotspots, but was less effective for solid inerting of nano Ti powder. Even with 80% nano TiO2 powder, the MITH of nano Ti/TiO2 mixtures was still less than 500 degrees C. Mixtures containing nano TiO2 powder prolonged the ignition delay time of micro Ti powder. Upon ignition by hotspots, pulsating flames occurred for micro or nano Ti powder clouds, and the flame spread velocity (FSV) of nano Ti powder was far greater than that of micro Ti powder. A small amount (e.g., 10%) of TiO2 increased the dispersibility of micro and nano Ti powders, thereby enhancing FSV values. Nano TiO2 percentages of at least 50% and 90% were required to completely suppress propagation of micro and nano Ti flames, respectively.