Abstract: A gas irradiation apparatus has a housing assembly having a gas inlet and a gas outlet. An irradiation chamber is contained within the housing, there the irradiation chamber has a first chamber, an adjacent second chamber, and an intermediate wall separating the first chamber from the second chamber. One or more conduits extend through the intermediate wall, which provide the exclusive flow path between the first chamber and the second chamber. A gas transfer fan is disposed within each conduit, with the gas transfer fans configured to induce flow between the first chamber and the second chamber. An array of light emitting diodes are configured to provide UVC light radiation into the irradiation chamber thereby irradiating any gas contained within the irradiation chamber.