An instrument for rapidly obtaining samples of airborne dust; a type of dust counter. Particles pass through a cylindrical chamber and are drawn at high velocity through a narrow slit in front of a microscope cover glass. The fall in pressure due to expansion of the air passing through the slit causes the formation of a moisture film on the glass to which the dust adheres. An analysis for quantity and size of the particles on the cover glass is made with the aid of a microscope. The vacuum required to operate the instrument is developed by an attached hand pump.