Abstract: A damper box includes a curved wall, an outlet, a side wall, and filter and a damper. The curved wall has an outside surface, an inside surface, and a separator sandwiched between an outside air inlet and a recirculated air inlet. The side wall is disposed between the recirculated air inlet and the outlet. The filter has a curvature matching the curved wall and covering the outside surface of the curved wall. The damper has an axis of rotation adjacent to and in alignment with the separator. The damper has a first face and a trailing edge. The first face is curved and configured to mate with a curved frame disposed about the outside air inlet. The trailing edge is configured to mate with the side wall. A ratio of outside air to recirculated air is modulated in response to the damper being rotated.

Abstract: A damper box includes a curved wall, an outlet, a side wall, and filter and a damper. The curved wall has an outside surface, an inside surface, and a separator sandwiched between an outside air inlet and a recirculated air inlet. The side wall is disposed between the recirculated air inlet and the outlet. The filter has a curvature matching the curved wall and covering the outside surface of the curved wall. The damper has an axis of rotation adjacent to and in alignment with the separator. The damper has a first face and a trailing edge. The first face is curved and configured to mate with a curved frame disposed about the outside air inlet. The trailing edge is configured to mate with the side wall. A ratio of outside air to recirculated air is modulated in response to the damper being rotated.

Abstract: A filter element is disclosed. The filter element includes an angled first end cap and a second end cap, each having angled surfaces. The first and second end caps each include an inner sidewall and an outer sidewall projecting longitudinally from the respective angled surfaces. The outer sidewall is axially spaced apart from the inner sidewall. Further, the inner sidewall defines a centrally disposed through-hole on the respective first and second end caps. The filter element also includes a filter media disposed between the first and second end caps. A first and a second locking mechanism are respectively provided on the first and second end caps. Further, the second locking mechanism of the filter element is configured to abut completely with the first locking mechanism of another filter element.