The physical conditions under which suprathermal grains can be produced when they are accelerated by radiation pressure against the drag of ambient gas are investigated. It is found that dust grains may attain a terminal velocityU (=105 cm s−1) in most regions and move out of the midplane of the source region about a distance |z|≤100 pc. Once clear of the main gas/dust layer the dust grains (a≃3×10−6 cm) may then attain ‘suprathermal energy’ (V g ≃3×108 cm s−1) by the Fermi process.