The influence of nocturnal ventilation reduction on indoor air quality.

The energy saving practice of stopping ventilation systems at night may reduce the daytimeair quality. Sorption phenomena where pollutants absorbed at night are reemitted during theday and the general slower removal of pollutants at the reduced average ventilation rates willcontribute to the deterioration of air quality at intermittent running systems. The purpose ofthe study was to investigate the impact on construction product emission during the day fromreduced ventilation rates at night. Experiments were performed in three small-scale chambersof Climpaq type with dilution systems. An untrained panel of approximately 45 humansubjects assessed the air quality in terms of acceptability. It was found that the intermittentventilation reduces the daytime air quality significantly for the investigated new surfacematerials. If the ventilation is stopped 12 hours every night, the increase in ventilation ratesrequired to maintain the same air quality as for continuous ventilation may be more than100%.