Abstract: An air exchange system for use in commercial and residential buildings for monitoring the concentration of carbon monoxide or other gaseous components of air present in the building, and for removing the carbon monoxide from the air upon reaching a predetermined threshold concentration. The system utilizes standard carbon monoxide detectors located in rooms on all floors of the building which are electrically connected to a central control unit. When an excessive level of carbon monoxide is detected by one or more of the detectors, the control unit triggers shut-down of all potential sources of carbon monoxide within the building. The control unit simultaneously reverses the flow of air through the central heating/air conditioning system to remove the ambient room air and any carbon monoxide present at floor level and vents the room air to the outside of the building while bringing fresh air into the building.