  We discuss chiral separation effect in the systems with spatial non -
homogeneity. It may be caused by non - uniform electric potential or by another
reasons, which do not, however, break chiral symmetry of an effective low
energy theory. Such low energy effective theory describes quasiparticles close
to the Fermi surfaces. In the presence of constant external magnetic field the
non - dissipative axial current appears. It appears that its response to
chemical potential and magnetic field (the CSE conductivity) is universal. It
is robust to smooth modifications of the system and is expressed through an
integral over a surface in momentum space that surrounds all singularities of
the Green function. In itself this expression represents an extension of the
topological invariant protecting Fermi points to the case of inhomogeneous
systems.
