In accordance with one aspect the present invention may comprise a regenerative blower comprising: a housing, a first port and second port in the housing, an airflow channel extending between the first and second ports for airflow between the ports, an impeller rotatable in an impeller channel to promote airflow in the airflow channel from the first port to the second port, a motor to drive the impeller, and an interrupter between the first and second ports to limit airflow from the second port to the first port.
