Relationships between bed operation in a fluid bed aerosol generator and aerosol output were studied. A 2 in. diameter fluid bed aerosol generator (FBG) was constructed using stainless steel powder as a fluidizing medium. Fly ash from coal combustion was aerosolized and influence of FBG operating parameters on aerosol mass median aerodynamic diameter, geometric standard deviation (.rho.g) and concentration was examined. In an effort to extend observations on large fluid beds to small beds using fine bed particles, minimum fluidizing velocities and elutriation constant were computed. Although FBG minimum fluidizing velocity agreed with calculations, FBG elutriation constant did not. Properties of aerosols produced by FBG depend on fluid bed height and air flow through the bed after the minimum fluidizing velocity is exceeded.