The effect of duct cleaning on perceived air quality in two office buildings.

The aim of this experiment was to study the effect of air duct cleaning on the indoor air quality. Three buildings in the Helsinki metropolitan area were selected for the study. In two of the test buildings the ducts were cleaned using three different cleaning methods. The third building serves as a control where no cleaning was done. The air handling systems in the test buildings had operated 26 and 30 years without cleaning. The air quality in the buildings was evaluated by using a trained sensory panel, and tested by the occupants in all these buildings by repeating self-administered questionnaires before and after the cleaning. A trained sensory panel was used to evaluate perceived air quality. The effect of cleaning on the amount of dust in duct system was measured with an optical method. The amount of dust decreased significantly in all the cleaning methods. Significant differences in the cleaning results between the three cleaning methods were observed. The cleaning of supply air ducts had an effect on indoor air quality perceived by the panel. The panel perceived the air quality worse on the decipol scale after the cleaning than before it. On the other hand, the occupants perceived the indoor air quality as more acceptable after duct cleaning than before it. The improvement was statistically significant in the building with a larger number of occupants. The occupants in both buildings also complained less of dusty surfaces after the cleaning than before.