A method for the indirect determination of the waste gas rate in metallurgical processes. A reference gas such as helium is first added to the waste gas, specifically at a time which, with respect to flow, sufficiently precedes the taking of a sample such that a thorough mixing of the reference gas and waste gas is carried out, i.e., a virtually homogeneous distribution is achieved, and a quantitative helium analysis and nitrogen analysis of the waste gas, measured by a mass spectrometer, is carried out while taking into account the added amount of helium.