[AIVC, Air infiltration and ventilation glossary, 1992]:A ventilation strategy where the airflow rate is governed by a chosen pollutant concentration level. This level is measured by air quality sensors located within the room or zone. When the pollutant concentration level rises above a preset level, the sensors activate the ventilation system. As the occupants leave the room the pollutant concentration levels are reduced, and ventilation is also reduced. Common pollutants are usually occupant dependent, such as, carbon dioxide, humidity or temperature.[ASHRAE Standard 62.1]:any means by which the breathing zone outdoor airflow (Vbz) can be varied to the occupied space or spaces based on the actual or estimated number of occupants, ventilation requirements of the occupied zone, or both.[EN 16798-1:2019, 3.11]:ventilation system where airflow rates are controlled automatically according to measured needs at room level.[EN 16798-3:2017, 3.6]:ventilation system where the ventilation rate is controlled by air quality, moisture, occupancy or some other indicator for the need of ventilation.