An installation for surface treating, in particular painting, objects, in particular vehicle body parts, having a treatment booth which defines a treatment space in which a booth atmosphere prevails. The objects can be transported into the treatment space and out of it again by means of a transport system. Treatment of the objects in the treatment space can be carried out by means of at least one treatment unit which requires a process gas for the operation. The process gas can be supplied to the at least one treatment unit by means of a supply device, wherein the process gas arrives in the treatment space during the treatment procedure and thus contributes to the booth atmosphere. A separating system is provided, to which booth atmosphere can be supplied and by means of which process gas can be separated from the booth atmosphere. A corresponding process is moreover disclosed.