A dynamic model is developed based on the preliminary set of assumptions to determine the viability of a pulsed Ultra-Rapid Pressure Swing Adsorption (URPSA) air-separation process using a 5A zeolite monolith adsorbent. The new model was shown to predict the performance of the Rapid PSA process investigated experimentally in 1986 by Pritchard and Simpson. The model predicts that single-stage URPSA is capable of producing oxygen purities of 85%, product recoveries of around 60%, and a bed-size factor of around 0.00073. A very, small bed-size factor and large product recoveries tire characteristic of this novel process, which implies improved efficiency of separation per unit mass of adsorbent material. The model developed here provides the first assessment of the viability of ultra-rapid cycles and thin monolithic adsorbents for air separation by PSA. (C) 2004 American Institute of Chemical Engineers AIChE J. 50: 953-962, 2004