Field studies of the indoor air quality by photoacoustic spectroscopy

Abstract Photoacoustic spectroscopy (PAS) was utilized for determination of the concentration of several airborne contaminants in buildings situated in urban environments. The investigations reported in this paper were carried out in four residential buildings, but comparisons are also made with results obtained at previous field studies in office buildings. In the buildings studied, the concentrations of carbon dioxide, carbon monoxide, formaldehyde, and the total concentration of volatile organic compounds were investigated by continuous monitoring with PAS instruments. The studies usually included monitoring periods of several days or weeks, and measurements in supply air, exhaust air, room air, and outdoor air at the air intakes to the buildings. The results indicate that the PAS technique is applicable for monitoring of the contaminants mentioned, but also that the interference between various contaminants is a disadvantage with this technique. The limitation in question is of special concern as regards measurements of the total volatile organic compounds, where the methane background is disturbing. A solution to the problem with the methane interference is, however, suggested in the paper. In this paper, some comparisons are also made between the results obtained by monitoring with PAS instruments and the results obtained by measurements with other types of instruments or by the use of other techniques, for instance, determination of the total concentrations of volatile organic compounds by GS/FID technique.