A kit for extermination of pest animals in furniture and a method for using the kit are disclosed. A sheet is provided over upholstered furniture. The sheet may be provided with ballast at the edges for keeping the sheet more or less fixed. Heated air is forced underneath the sheet. The furniture is preferably provided with an air treatment module for forcing air through the upholstery like a mattress. This allows the heated air provided by the forced air supply to be provided to the upholstery via the inside, highly increasing efficiency of heat treatment of the furniture. A way of controlling temperature of air provided by the forced air supply is disclosed, as well as a way of controlling temperature of air actually within the spaced defined by the positioned sheet. The latter allows for improved control of maintaining a temperature at which for example bed bugs are killed.