Nano-sized (e.g., 7nm primary particle size) fumed silica particles typically exhibit an ultra-high negative triboelectric charge-to-mass ratio (q/m) when agitated with micron-sized (e.g., 50 to 100μ diameter) carrier beads. Micron-sized toner particles (e.g. 5 to 9μ diameter) also exhibit an increasingly negative charge when fumed silica particles are applied as external additives to their surface.In this present report, a quantitative analysis of triboelectric charging data from mixtures of fumed silica particles and carrier beads is presented, based on a mechanistic model for triboelectric charge generation. The model is also used to illustrate the connection between the triboelectric charging properties of fumed nano-sized silica particles and the charge level of external additive micron-sized toners