  The Statistical Model has to be formulated in the canonical ensemble with
respect to strangeness conservation if the number of strange particles becomes
small. However, the canonical suppression under the assumption of strangeness
chemical equilibrium in the whole fireball volume was found to be not
sufficient to reproduce observed yields. Two approaches have been proposed to
modify the model. First, a non-equilibrium factor was introduced in canonical
and grand-canonical ensembles as the additional fit parameter to account for
the suppressed strange particle phase-space. Here we focus on the second
method: The model is extended by correlation volumes which restrict the
strangeness chemical equilibrium only to certain subvolumes of the system.
