Adsorption experiments of SO 2 on activated carbon has been carried out for low concentrations (about 100 ppm) at room temperature (15 to 33 Β°C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO 2 concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO 2 . When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO 2 concentration at the exit of a fixed-bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO 2 and H 2 O are desorbed at low temperatures. At higher temperatures, the MS peak of SO 2 and H 2 O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO 2 disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO 2 from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process.