In the framework of a project of the International Energy Agency (IEA) , IEA-Annex XVIII - Demand Controlled Ventilating (DCV) Systems, which started in fall 1987, a review of the state of the art of already existing DCV systems and devices has been undertaken by all participating countries. This paper is concerned with air quality sensors which may be suitable to control air quality on demand. The dominant contaminants are not only variing in different kinds of buildings (dwellings, schools, stores etc.) but also from room to room due to different ways of utilizing the spaces.
In order to avoid demage to the health of occupants, annoyance or reduction in amenity and demage to the building fabric the concentration of indoor air pollutants has to be held below pollutant specific levels. One appropriate measure for the control of concentration is ventilation. In several national and international activities in the past, among others in the IEA's Annex IX "Minimum Ventilation Rates" and standardization efforts in Germany and other countries, ventilation rates have been defined which should meet both indoor air quality (iaq) requirements and energy conservation.
Good indoor air quality and thermal comfort and good energy-efficiency can be achieved simultaneously only if the amount of ventilation can be demand-controlled. Two approaches are discussed in the article: CO2- control and use of so-called air quality sensors. The first experiments have been promising but further development of equipment is still needed, in order to improve the reliability and economy of demand-controlled ventilation.
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