  We present the results of a multiline survey at mm-wavelengths of the Cepheus
A star forming region. Four main flows have been identified: three pointing in
the SW, NE, and SE directions and accelerating high density CS clumps. The
fourth outflow, revealed by high-sensitivity HDO observations, is pointing
towards South and is associated with conditions particularly favourable to a
chemical enrichment. The analysis of the line profiles shows that the SiO
molecule dominates at the highest velocities and at the highest excitation
conditions, confirming its close association with shocks. H2S, SO2, and SO
preferentially trace more quiescent regions than SiO, and in particular a lack
of bright H2S emission at the highest velocities is found. OCS and H2CS emit at
quite high velocities, where the abundances of three shock tracers like SiO,
CH3OH, and HDO are higher. These results may indicate that H2S is not the only
major sulphur carrier in the grain mantles, and that OCS and H2CS may probably
play an important role on the grains; or that alternatively they rapidly form
once the mantle is evaporated after the passage of a shock. Finally, the
outflow peak emission has been compared with recent time-dependent sulphur
chemistry models: the results indicate that, if associated with accurate
measurements of the physical conditions, the CH3OH/H2CS column density ratio
can be used as an effective chemical clock to date the age of shocked gas.
