  We have analysed a sample of 23 hot DAs to better understand the source of
the circumstellar features reported in previous work. Unambiguous detections of
circumstellar material are again made at eight stars. The velocities of the
circumstellar material at three of the white dwarfs are coincident with the
radial velocities of ISM along the sight line to the stars, suggesting that the
objects may be ionising the ISM in their locality. In three further cases, the
circumstellar velocities are close to the ISM velocities, indicating that these
objects are either ionising the ISM, or evaporated planetesimals/material in a
circumstellar disc. The circumstellar velocity at WD 1614-084 lies far from the
ISM velocities, indicating either the ionisation of an undetected ISM component
or circumstellar material. The material seen at WD 0232+035 can be attributed
to the photoionisation of material lost from its M dwarf companion. The
measured column densities of the circumstellar material lie within the ionised
ISM column density ranges predicted to exist in hot DA Stromgren spheres.
