Abstract: An apparatus for the continuous thermal treatment of a product within an atmosphere made up of steam (saturated or superheated) of pure water or of a mixture of air and water vapor is disclosed. The product moves through an enclosed or confined space for its thermal treatment by the steam. The space is provided with entry and exit air-locks for the conveyance of the product into the space and for its removal. There are also means for guiding the product through the air-locks and the space. Additional means is provided to encourage thermal treatment and hence the space is provided with convection, radiation or conduction means to bring heat to the product. A first condensor receives vapor or humid air which is preferably extracted from the enclosed space via the adjacent air locks; it provides heat recovery of the purged vapor from the space. A second condensor is placed within the enclosed space and communicates with the high pressure discharge port of a compressor.