Duration of one measurement cycle is approximately 90 s. The cycle can be roughly divided into the desorption, flushing and adsorption phases. Figure demonstrates the measurement cycle and how the sorbent temperature evolves over time. It should be noted that the measurement is continuous and cyclic. Here, we have arbitrarily chosen to explain the sampling cycle from the point of view of the spectroscopic measurement, in the sense that we start from the desorption phase, where the sample exchange into the CEPAS cell takes place. The adsorption phase, which happens parallel to the CEPAS measurement, is explained last. In the desorption phase, an enriched sample is transferred from the sorbent tube into the CEPAS cell. During the transfer, there is no gas flow from the input through the sorbent. Instead, the gas from the sorbent tube is transferred passively into the cell by first evacuating the cell and then opening the valve between the evacuated cell and the sorbent tube. To ensure that there is enough gas volume to transfer the desorbing gases throughout the sorbent, there is an extra volume of about 10 mL behind the sorbent tube (see V d in figure ). Figure depicts the steps of the gas exhange. It should be noted that figure starts from the end of the adsorption phase (figure ). In the beginning of the desportion phase, the valves before and after the sorbent tube are closed, and the heating of the sorbent tube is initiated (figure ). While the sorbent is heating up, the CEPAS cell is evacuated to a pressure of 150 mbar. When the sorbent temperature is measured to be over 100 °C, the heating is stopped and the forced air cooling of the sorbent tube is turned on. The flow direction is set into the backward flow direction (see figure ) and the valve between the sorbent tube and the CEPAS cell is opened (figure ). The input valve is still closed, but the gas from the extra volume V d ex-pands through the sorbent towards the evacuated CEPAS cell, transporting the enriched sample gas into the cell. At this stage, the cell pressure rises to approximately 440 mbar. The valve between the cell and the sorbent tube is then closed, and the cell pressure is evacuated to the measurement pressure, which in our measurements is 200 mbar. The low pressure is required to reduce the spectral interference from the CO 2 line. With the enriched sample inside the CEPAS cell, the spectrum measurement is initiated together with the flushing phase of the enrichment.