  A cornerstone of AGN unification schemes is the presence of an optically and
geometrically thick dust torus. It provides the obscuration to explain the
difference between type 1 and type 2 AGN. We investigate the influence of the
dust distribution on the Eddington limit of the torus. For smooth dust
distributions, the Eddingtion limit on the dust alone is 5 orders of magnitudes
below the limit for electron scattering in a fully ionized plasma, while a
clumpy dust torus has an Eddington limit slightly larger than the classical
one. We study the behaviour of a clumpy torus at low and high AGN luminosities.
For low luminosities of the order of ~10^42 erg/s, the torus changes its
characteristics and obscuration becomes insufficient. In the high luminosity
regime, the clumpy torus can show a behaviour which is consistent with the
"receding torus" picture. The derived luminosity-dependent fraction of
type-2-objects agrees with recent observational results. Moreover, the
luminosity-dependent covering factor in a clumpy torus may explain the presence
of broad-line AGN with high column densities in X-rays.
