  As a generic model for liquid-vapour type transitions in random porous media,
the Asakura-Oosawa model for colloid-polymer mixtures is studied in a matrix of
quenched spheres using extensive Monte Carlo (MC) simulations. Since such
systems at criticality, as well as in the two-phase region, exhibit lack of
self-averaging, the analysis of MC data via finite size scaling requires
special care. After presenting the necessary theoretical background and the
resulting subtleties of finite size scaling in random-field Ising-type systems,
we present data on the order parameter distribution (and its moments) as a
function of colloid and polymer fugacities for a broad range of system sizes,
and for many (thousands) realizations of the porous medium. Special attention
is paid to the connected and disconnected susceptibilities, and their
respective critical behavior. We show that both susceptibilities diverge at the
critical point, and we demonstrate that this is compatible with the predicted
scenario of random-field Ising universality.
