  Context. Dust in active galactic nuclei is clearly present right outside the
broad-line region (BLR) in the form of a dusty molecular torus. However, some
models of the BLR predict that dust may also exist within the BLR. Aims. We
study the reprocessing of radiation by the BLR with the aim of observing how
the presence of dust affects the reprocessed continuum and the line properties.
Methods. We calculated a range of models using the CLOUDY photoionisation code
for dusty and dustless plasma. We paid particular attention to the well-studied
object NGC 5548, and we compared the line equivalent width predictions with the
data from observations for this object. Results. We obtained a rough agreement
between the expected equivalent widths of the H$\beta$ and Mg II lines and the
observed values for NGC 5548 for the line distances implied by the time-delay
measurement (for H$\beta)$ and the radius-luminosity relation (for Mg II) when
the medium is dusty. We found the incident radiation to be consistent with the
radiation seen by the observer, so no shielding between the inner disc and the
BLR is required. High ionisation lines such as He II, however, clearly form in
the inner dustless region. When the additional absorber is present, the
H$\beta$ emitting region moves closer to the dustless part of the accretion
disc surface.

Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics