Abstract: A method of continuos thermal treatment of a textile product web has the steps of bringing a product web in contact with a treatment gas guided in a circulating process, introducing a product web into a steam portion having one or several steam stages in which heat steam is used as a treatment gas, introducing the product web into a steam-air portion which has one or several stages and hot steam and heated air as a treatment gas, passing the product web first through the steam portion and subsequently through the steam air portion, providing an exchange of the treatment gas between the steam stages and the stages, adjusting a relative moisture of the hot steam of the steam stages of the steam portion to the value zero, and performing the adjusting by measuring relative moistures of a first and a last steam stages and changing discharge gas quantities of the first or second steam stages and one further stage.