Neutron flux irradiation was used to modify the surface properties of activated carbon as a means to increase the amount of moisture adsorption on the modified activated carbon samples. The activated carbon was first dropped into the saturated boric acid solution to make the boron-doped activated carbon. The dried boron-doped activated carbon sample was further irradiated by neutrons to produce the alpha particles (He-4(2)). The alpha particles bombarded the activated carbon randomly to enhance the microscopic damages and/or to increase the micropore zones. As a result, the effective surface area on the activated carbon was increased and the amount of adsorption per unit volume of absorbent was increased also. An equipment to measure the breakthrough curves of water vapor adsorption on the activated carbon samples was built in this study. A computer real-time control for data logger was also designed successfully for recording the data points in the breakthrough curves. The BET sorptometer was used to measure the surface properties of the adsorbents in this study. Under the operating conditions, the amount of moisture adsorption by the modified activated carbon increased by more than 18.8 % of that of the original activated carbon sample.