The invention relates to a method for quantitative analysis of the composition of a gas mixture, in particular of the atmosphere of a containment (4) of a nuclear plant. The method is intended to make it possible to easily and reliably determine, in as direct a manner as possible, even under difficult conditions, physical parameters which characterize the ignition field and the combustion behaviour of the gas mixture. For this purpose, a measuring device (2) is provided according to the invention which comprises • a thermal conductivity detector (16) having a first measuring bridge, • a reaction heat detector (14) having a second measuring bridge, and • a common evaluation unit (26), wherein the hydrogen (H2) content and at the same time the oxygen (O2) content are determined in the evaluation unit (26) based on the bridge voltages present at the two measuring bridges.
