Circuit arrangement for evaluating a signal provided by an air quality sensor

The circuit has a stage for signal evaluation (12) using at least one criterion that outputs a switching signal with a first state corresponding to high air quality and a second corresponding to low quality. An integrator (27) increases a characteristic value for the second state and reduces it for the first state and a comparator (34) compares the characteristic value with a threshold and produces at least one correction signal (36,37).