Everyone became much more concerned about ventilation rates and indoor air quality with the formulation and revision of ASHRAE Standard 62.1-1999. With the increased attention on proper ventilation in buildings, some started to wonder whether the old way of doing things - usually constant air volume, or more recently variable-air volume (vav) - was really the best way of providing proper ventilation to a building. Then along came CO2-based demand control ventilation (DCV).
A CO2-based DCV system utilizes an air quality sensor (carbon dioxide) to determine the occupancy level for the building space. If there is one person in the space, the outdoor dampers can cut down on the amount of outside air being brought in. Obviously, if there are more people in a space, the system brings in more outside air. This system can save energy for the building owner as well as improve indoor air quality in the building by bringing in outside air when it is needed by the occupants.