Abstract: Disclosed is a virtual impactor for separating particles of a predetermined size range from an aerosol, and for transporting the separated particles from the region they are separated from the aerosol to an analysis/collection region remote therefrom. The device comprises a conduit member having an inlet end and an outlet end. The conduit member is configured to define a substantially enclosed passageway between the inlet end and the outlet end. At least a portion of the conduit member is gas-permeable. The outlet end of the conduit member is positioned adjacent to the analysis/collection region. The virtual impactor is moved relative to the aerosol to be sampled (or the aerosol is moved relative to the impactor). The virtual impactor utilizes an operating gas that is introduced into the impactor through the gas-permeable portion of the conduit member.