Continuous removal of SO 2 as aqueous H 2 SO 4 over polyacrylonitrile-based activated carbon fibres (PAN-ACF) was studied kinetically at room temperature to determine the effects of SO 2 (20-1000 ppmv), O 2 (0-10 vol.%) and H 2 O (0-10 vol.%) concentrations and W/Q ratio (mass of ACF/volumetric flow rate of gas). An oxygen level > 3 vol.% was sufficient to provide steady-state removal of SO 2 . Higher inlet SO 2 concentrations gave higher SO 2 outlet concentrations, while more H 2 O and a higher W/Q ratio increased the SO 2 removal. On the basis of this kinetic study, the rate-determining step is postulated to be aqueous H 2 SO 4 desorption from the ACF bed, which makes sites available for further SO 2 adsorption. Hence a lower SO 2 concentration, more H 2 O, and a higherW/Q ratio are compensating factors in achieving the complete removal of SO 2 by continuous recovery of aqueous H 2 SO 4 at the outlet.