The document applies the performance testing of space heaters mounted in a shaft under the surface of the floor. The dimensions of the space heaters and the shaft shall enable the testing of the system, i.e. the deviations of the meaurred values may not exceed those given in DIN 4704-1. It applies also to underfloor heaters with fans provided that the heater and the fan manufactured as a unit. DIN 4704-5 applies additionaly.#,,#