  We use photometric data, from the optical to the mm for a large sample of
optically selected radio-quiet quasars, at low and high redshifts, to test
emission models from circum-nuclear dusty torii around them. Model parameters,
such as dust mass, temperature distributions and torus sizes are inferred,
under the assumption that the dust is heated only by the central nuclear
source. Dependences of best-fit parameters on luminosity and redshift are
studied and the contribution of dust in the host galaxy to the observed fluxes
is briefly mentioned. Only tentative conclusions can be drawn from this yet
large dataset and detailed modelling, because crucial spectral information is
missing at wavelengths where the QSO dust emission is more prominent, i.e. at
$\lambda \simeq 50$ to 600 $\mu m$. Poor information in this wavelength range
affects our understanding not only of the high-redshift objects, but also of
the low-redshift sample. We then expect fundamental contributions by the FIRST
mission in this field, which is obviously related to the more general one of
galaxy formation.

Astrophysics