The CO2 concentration in a room varies depending on the number of people in it. An empty room generally has a concentration of about 400 ppm (normal outdoor concentration). The CO2 concentration in the room will then increase for each person added.
Therefore, a small Demand Controlled Ventilation system can be a good idea. This system has a sensor that measures the CO2 value and sends a signal to a ventilator or a VAV-device that then changes the level of ventilation required in the room. The system also has variable dampers that are usually used to regulate the airflow through the sensor.
A minor ventilation system is an intelligent sensor or analyser that is adjusting one fan in the same room. This fan regulates the airflow.
This application saves a lot of money in the form of energy savings. Room fans will only operate for as long as they need to, based on the level of CO2 in the environment. This reduced use of energy is also good for the environment and is an obvious way to conserve the earth's resources.
Tests on buildings that are using Demand Controlled Ventilation show that energy costs are reduced by about 30%. This can lead to a return on investment in about 1 year.