An apparatus for treating objects with a treatment gas comprises a treatment chamber, a chamber input through which objects enter the treatment chamber, and a chamber output (which may be the same as the chamber input) through which the objects leave the treatment chamber. The treatment chamber encloses the treatment gas, which can be steam. The chamber output and/or the chamber input include an intermediate medium, such as a liquid, through which the objects pass. The intermediate medium prevents escape of the treatment gas from the treatment chamber and the ingress of external gases into the treatment chamber, while facilitating input of the objects to the chamber, and output of the objects from the chamber.
