A multi-unit system combines multiple single bed reversing blower vacuum swing adsorption air separation units together. The units feed a common O2 supply such as a system buffer tank. Demand is monitored and a number of individual units are brought online sufficient to meet demand. If demand exceeds supply, a further unit is brought online. If demand drops below supply by an amount greater than output of a single unit, then a longest operating unit is taken offline. The multi-unit system thus meets demand through utilization of multiple separate units in a highly redundant and highly reliable and scalable fashion.