Sorbent is flushed into backwards direction (see figure (1) for approximately 30 s after the desorption phase, when the sorbent temperature is still high. Here we used sample gas for flushing, since very little benzene is retained in the sorbent when the temperature is well over its boiling point. In principle, better accuracy could be expected if, for example, clean nitrogen or another input equipped with an active carbon filter was used for the flushing, but in most practical cases we expect the improvement to be marginal. After the flushing phase, the ad- ). It should be noted that the sorbent temperature is changing during the adsorption phase in our measurements. In the beginning, the temperature is still so high that a part of the adsorption time is effectively wasted, since the breakthrough volume is small and very little benzene is absorbed. According to our measurements, we estimate that once the sorbent temperature drops below 80 °C, practically all of the benzene is retained. The effective adsorption time where the sorbent temperature is below 80 °C in our measurements is approximately 30 s. During the flushing and adsorption phases, which take approximately 60 s, the sample spectrum is measured from an enriched sample inside the CEPAS cell and the benzene concentration is calculated as described in the previous section. After the spectrum is measured, the gas flow is stopped and the desorption phase is initiated again, starting a new measure-ment cycle.