A method is suggested for determining an absolute gas concentration. The method employs a gas sensor arrangement comprising a gas sensor (1) and means (11, 12) for decomposing a gas to be measured. Furthermore, the method comprises the steps of acquiring a first sensor signal and determining from the first sensor signal at least one initial data point. Then the gas to be measured is decomposed using the means (11, 12) for decomposing the gas of the gas sensor arrangement. A second sensor signal is acquired and from the second sensor signal at least one decay data point is determined. Finally, an absolute gas concentration is determined from a gas concentration function by evaluating the gas concentration function at least for the initial data point and the decay data point.