To obtain accurate kinetics of adsorption pairs, dynamic tests of a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) and ammonia were performed on small samples under isothermal conditions and on a larger quantity in a laboratory scale adsorption system. The experimental results show that the size of the pressure swing plays an important role in the dynamics of adsorption pairs. This driving pressure difference affects the mass transfer of NH 3 through the pores of adsorbent and therefore the performance of the complete adsorption system. A modified LDF (Linear Driving Force) model was used to fit the experimental results.It was shown that the model can predict the dynamics of both adsorption and desorption fairly well and can be used for the modelling of the adsorption system and adsorption cycles.