This study describes the behaviour of particles with equivalent diameter 205 µm (fine sand, according to the classification of sedimentary particles based on the Wentworth scale), fluidized by air in a 100 mm vertical Perspex column, with the bed open to the atmosphere. The pressure drop in bed for different gas velocities has been measured using the fast response pressure transducers connected to the column. The signals from two transducers were continuously recorded on a computer and the records of drop pressure versus time were obtained.