Abstract: An apparatus for generating high purity oxygen is described which comprises a linear actuator, a dual acting air cylinder, two molecular sieve beds, and valving. The linear actuator drives the air cylinder back and forth, compressing air on both the forward and return stroke. On each stroke, fresh air is compressed into one of the beds, generating oxygen. Simultaneously, the opposite bed exhausts to ambient pressure and the non-compressing side of the cylinder draws in fresh air. The cylinder then reverses, which compresses air into the opposing bed and allows the first bed to exhaust.