The measurement system is constantly monitoring the sorbent temperature and the flow rate at the sample input, since these have an impact on how much benzene is retained in the sorbent. The sample flow rate into the measurement system during the adsorption phase is approximately 0.5 L min -1 . In the laboratory measurements reported here, we didn't observe much variation in these parameters, and the repeatability was good without any corrections. In field measurements however, for example if the ambient temperature varies significantly, it may be necessary to calibrate the sorbent enhancement with factors tied to the sorbent temperature and the sample mass flow rate.