  The effects of gravitational settling and radiative levitation in the stellar
atmospheres and envelopes of subdwarf B (sdB) stars strongly depend on the
presence of weak winds. In the paper the existence of weak radiatively driven
winds is investigated from a theoretical point of view for sdB stars of half a
solar mass, effective temperatures between 25000 K and 35000 K, and surface
gravities log g between about 5.0 and 6.0 (cgs units). According to the
results, weak winds with mass-loss rates of the order E-11 solar masses per
year may exist only for the most luminous sdB stars. For the more compact ones,
the decoupling of the metals from the bulk matter (hydrogen and helium) is
expected in the wind region, because the momentum exchange via Coulomb
collisions is not effective enough. Thus multicomponent effects are of great
importance. We suggest that only the metals may be expelled from the star,
whereas hydrogen and helium are in hydrostatic equilibrium.
