The HMI Hoyme Manufacturing Inc. universal air control damper series 'HAC' is an effective damper to control incoming air in both hot and cold climates. This damper is fully controlled by your home heating or cooling system to safely and efficiently supply fresh air for your comfort. During hot summer months incoming air will not overload your cooling system and during cold winter months will not damage your heating system. Each damper has a mounting collar which allows easy installation to your return plenum. This damper is equally effective in providing significant energy savings for both standard and high efficiency furnaces.