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Adsorption, Desorption, and Chemical Reactions in the Particulate Matter Collected on Air Filters and Ducts
Principal investigator: Prof. Pentti Kalliokoski, Department of Environmental Sciences, University of Kuopio, e-mail: pentti.kalliokoski@uku.fi

Even though air handling systems are intended to improve indoor air quality and climate, they have often become major sources of odorous compounds. The filter has usually been the main cause of sensory pollution, and its emission has increased with time. Dirty ducts and coils have also remarkable odor emissions. Already the new ducts are often heavily contaminated with processing oil residues and with dirt accumulated during storage and construction period of the building. On the other hand, it has been found that the sum of the odors released from various components may not be in good agreement with the perceived emission from the whole system. Adsoption and desorption processes between accumulated particulate impurities and gaseous pollutants seem to play an important role for the final air quality. In addition, chemical reactions between oxidizing pollutants, such as ozone, and the organic pollutants adsobed on particles have been suggested to occur and to further deteriorate the air quality.

In this study, the adsorption and desorption properties of dust collected on filters and other parts of the air handling units are investigated. Especially, the significance of adsorption and desorption phenomena on air quality is considered. The data are also used to model the interactions between particulate matter and gaseous compounds. The chemical reactions will be studied. The ultimate aim is to prepare guidelines for cleaning and maintenance.

Dust samples will be collected from office buildings locating in downtown areas of Helsinki and Kuopio. For comparison, samples will also be collected from buildings in clean suburban area in Kuopio. The properties, such as spesific surface area, density, carbon content, and carbon/nitrogen-ratio, affecting the adsorption/desorption properties will be determined. Used air filters will be installed into a laboratory scale air handling unit for further studies. The gaseous compounds that will be investigated include the common volatile organic compounds belonging to aliphatic hydrocarbons, aldehydes, terpenes, and aromatic compounds. In addition to the physico-chemical properties, the odor emissions from the dust samples and the effects of ozone will be determined.