In order to fulfill the measurement requirements of the 1st BImSchV, the combustion air temperature must be determined in the sucking area of the combustion plant. This requires temperature sensors fitted with magnet or fixation cone which can be placed in or by the sucking opening of the combustion plant. Wide common – but consequently not 1st BImSchV-conform – are so-called T-Room stick in use which are directly connected at the analyser and record the ambient temperature from there. In case the temperature at this point is differing from the temperature at the sucking opening, errors may occur by the determination of the gas losses. At the end of the day, practicability and required accuracy are the factors deciding about the use of a T-Room stick / T-Room sensor.