Q. What is Demand Control Ventilation (DCV)? A. Demand Control Ventilation (DCV) is an energy saving mechanism designed to reduce the activity of ventilation systems when low occupancy conditions permit. DCV is used in parking garages, movie theatres and other large areas where traffic is cyclical or intermittent. DCV limits the runtime of fans, compressors and other HVAC equipment. Sensors in the variable occupancy areas monitor CO2 and turn equipment on once a certain threshold is reached. DCV is typically paired with economizer repair in energy efficiency programs and is a highly desirable measure because of the relatively high kW savings compared with other more lighting-intensive programs.