A palladium catalytic oxidizer is being developed to remove plant-generated oxygen from a closed plant growth chamber, replacing the oxygen with carbon dioxide gas and water vapor. The device will provide a relatively simple means of preventing oxygen build-up within the chamber. It may also be used to simulate man-in-the-loop at whatever scale is desired. Discussion is provided on how the device fits in with the development of the closed plant growth environmental chamber in the short term and with controlled ecological life support systems (CELSS) development in the longer term. Alternative means of oxygen removal are compared. The results of preliminary kinetics testing is presented.