An air check valve system configured to be mounted for fluid communication with a fan can include a ring having a generally circular inner diameter that defines an air passage through a plane of the ring. A first and a second flange can extend from the ring. A rod can have a first end mounted to the first flange and a second end mounted to the second flange. The rod can define a pivot axis. A first and a second damper plate can be mounted to the rod for rotation around the pivot axis between an open and a closed position.