Pressure swing adsorption (PSA) is a process that uses high pressure to attract gas onto a solid surface. When the pressure increases, gas is adsorbed, and when the pressure decreases, the adsorbed gas is released. PSA can separate gases based on their attraction to different solid surfaces. For example, if air passes through a carbon molecular sieve (CMS) adsorption bed under pressure, the attraction of oxygen will be stronger than that of nitrogen, so oxygen will remain in the bed while nitrogen will be released. This bed can be reused by depressurizing and releasing adsorbed oxygen for another cycle of producing high-purity nitrogen gas. Two adsorbent containers can be used for almost continuous production and save energy through pressure balancing, where the gas leaving one container depressurizes the second container. This is a common industrial practice.