CONTROLLING VENTILATION RATES AND INDOOR AIR QUALITY

摘要

An apparatus (400) and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured and the volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor (104) is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller (46). Moreover, for calibrating the apparatus (400), a return air sensor (42) is calibrated to the outside air and a mixed air sensor (40) is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.