Containerized gas separation system comprising (a) a container having an interior, an exterior, and an exterior volume defined by the exterior dimensions of the container and (b) a pressure swing adsorption system installed in the interior of the container and adapted to recover a product gas from a feed gas mixture, the pressure swing adsorption system being adapted to deliver the product gas at a product gas flow rate, wherein the ratio of the exterior volume of the container to the product gas flow rate is less than about 2000 ft3/(ton per day).