Dust is released from a mechanically vibrated bed of cohesive powders aerated close to the minimum for fluidization. The materials tested were silica and potato starch. The effect of both vibration intensity and vibration frequency on dust formation are verified, and a model to account for these two variables has been developed. A dimensionless dust release parameter has been defined and calculated from the experimental results. This parameter is able to explain the role of the acceleration due to vibration and of cohesive interparticle forces, also accounting for the magnification effects of acceleration intensity close to resonance conditions. However, the same parameter is unable to fully account for changes in dust emission induced by fluidized bed bubbling promoted by vibration frequencies close to resonance. Without considering these effects, frequency determines a reduction of dust release that should be explained by introducing some effects other than those considered in our model.