  Dense environments have an impact on the star formation rate of galaxies. As
stars form from molecular gas, looking at the cold molecular gas content of a
galaxy gives useful insights on its efficiency in forming stars. However, most
galaxies observed in CO (a proxy for the cold molecular gas content) at
intermediate redshifts, are field galaxies. Only a handful of studies focused
on cluster galaxies. I present new results on the environment of one medium
mass cluster from the EDisCS survey at $z\sim0.5$. 27 star-forming galaxies
were selected to evenly sample the range of densities encountered inside and
around the cluster. We cover a region extending as far as 8 virial radii from
the cluster center. Indeed there is ample evidence that star formation
quenching starts already beyond 3 cluster virial radius. I discuss our CO(3-2)
ALMA observations, which unveil a large fraction of galaxies with low
gas-to-stellar mass ratios.
