Modelling the influence of outdoor pollutants on the indoor air quality in buildings with airflow rate control.

Low emitting building materials have contributed to the reduction of indoor air contaminants, and in many countries gas ranges and gas cookers are rarely used. As a result, in buildings located in urban environments, a considerable part of the contaminants in the indoor air may originate from the outdoor air. In urban areas buildings are exposed to high concentrations of a large number of contaminants, especially during traffic peak hours. Often, the air intakes are located on the facades, and if there are no filters, the supply air will have the same content of contaminants as the outdoor air adjacent to the buildings. Where if possible, it is advantageous to place the air intakes on the roofs of the buildings (1). The higher the air intakes are placed, the better is the air quality in most cases. To avoid exposure to high concentrations indoors due to concentration peaks of contaminants in the outdoor air, it is possible to decrease the airflow rate temporarily (2). This could be done by monitoring the concentration of carbon monoxide (CO) adjacent to the air intake. When the outdoor concentration of CO exceeds a preset limit, the fans are simply switched off, or the speed of the fans are decreased to a more suitable level.