  We calculate the temperature and ionization balance in an outflow from an
accreting black hole under illumination by hard radiation from the central
object. Electron scattering of the Fe K_alpha photons within the highly ionized
expanding flow leads to a decrease of their energy (redshift) which is first
order in v/c, when v is the outflow velocity and v is much less than the speed
of light c. This photon redshift is an intrinsic property of any outflow for
which divergence is positive. We also find that the equivalent widths of
red-skewed K_alpha originated in the wind is of order of keV. We conclude that
redshifted lines are intrinsic properties of the powerful outflows that are
observed in many compact objects. Downscattering of the primary line photons
generated in the outflow (a more natural and probable mechanism than the
general relativistic effects in the innermost part of the accretion flow) leads
to the formation of red-skewed lines.
