Abstract: A fresh air ventilation system in a building having an outside wall exhausts contaminants, such as stale or noxious air, through the outside wall and takes in fresh air. A remote switch sets a mode of operation of the ventilation system. One or more strategically placed air quality sensors are located within the building. The sensors may be connected wirelessly through a multiplexer interconnect system to operationally control the fan of the exhaust system. In response to the detection of a contaminant above a pre-selected level by a sensor, the relay controller for the sensors resets the remote switch for continuous high speed operation to evacuate the contaminants from the building through either special ducts or the conventional air ventilation ducts within the building.