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ABSTRACT This study was designed to investigate the impact of sorption processes on indoor air quality using human beings as measuring devices. The experiments were performed in four similar, adjacent, low polluting offices, where the pollution sources and the sorptive sinks were the actual room surfaces and the surfaces of the evaluated building materials (carpet, painted gypsum boards, and linoleum). An untrained panel assessed the air quality in the offices where the air was polluted either by individual building materials or by various combinations of two materials. In these experiments, the air polluted by two different building materials placed in the same room was perceived to be better than the air in a room polluted by the more polluting of the two materials. Presumably, the pollutants emitted from one material were sorbed on the surface of the other material and on the room surfaces, reducing the concentrations of the emitted sensory pollutants and affecting the perceived air quality. During the desorption period, after the strong pollution source was taken out of the room, more than three days of ventilation were required before the room air was perceived to be free of emissions from the polluting material. INDEX TERMS Building materials, sorption, linoleum, carpet, sensory measurements INTRODUCTION To a first approximation, the concentration of VOCs indoors depends on the emission rate of these compounds and the ventilation rate. However, a variety of studies have demonstrated that in the real indoor environment, indoor air pollutants interact with indoor surfaces by (adsorption/desorption) and this also influences the pollutants' concentration indoors (Baird et al. 1987, Seifert and Schmal 1987, Berglund al 1988, Borazzo et al. 1990, Tichenor et al., 1991; Jorgensen et al, 1993, Jorgensen et al, 1999, Colombo et al. 1993, Kephalopoulous et al. 1996, An et al. 1999, Won et al 2000, Won et al.2001; Singer et al. 2003, Singer et al. 2004). Materials capable of sorbing and desorbing pollutants influence indoor air quality during the entire life of the building (Nielson 1987). The influence can be both positive and negative, reducing the peaks of episodic pollutants, but prolonging their lifetime in an indoor setting. Many researchers have studied sorption by building materials to better determine its impact on the quality of indoor air. Using data collected in both static (Colombo et al. 1993, Kephalopoulous et al. 1996, Singer et al. 2004) and dynamic (An et al., 1999) chamber experiments; they have developed models to predict the sorption of chemical compounds to a variety of indoor surface materials. In most of these studies, samples of indoor materials were exposed to an artificially polluted atmosphere (one or several VOCs) with concentrations usually much higher than those found in typical indoor environments. The aim of the present study was to use sensory assessments to investigate the impact of sorption on indoor air quality under realistic conditions. METHODS Untrained panels assessed the air quality in four adjacent 40 m3 offices. Each office had one glass window on the external wall, floors consisting of low polluting polyolefin (13 m2), walls made of painted brick and ceiling tiles made of compressed mineral wool. The outdoor air was supplied to the test rooms by an axial fan and a damper mounted in each room’s window. The outdoor air was neither filtered nor conditioned. The room air was polluted either by individual building materials or a combination of two materials. The pollution source varied from one
Proceedings: Indoor Air 2005
SORPTIVE INTERACTIONS AMONG BUILDING MATERIALS AND THEIR RESULTANT IMPACT ON PERCEIVED INDOOR AIR QUALITY
W Sakr 1,3,*, CJ Weschler 1, 2, PO Fanger 1 1 International Center for Indoor Environment and Energy, Technical University of Denmark, DK-2800 Lyngby, Denmark 2 Environmental and Occupational Health Sciences entistry of New Jersey & Rutgers University, Piscataway, NJ 08854, USA 3 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, Canada
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Corresponding author email: ws78@
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Proceedings: Indoor Air 2005 office to another. Two offices had one material each (carpet, linoleum or painted gypsum board), and one had a combination of two materials (carpet and painted gypsum board or linoleum and painted gypsum board). The carpet was approximately 24 years old, taken from an office building. The gypsum board was painted (on both sides) six months before the experiment. The linoleum was 5 years old. The area of the material samples was chosen to match either that of the office floor (carpet and linoleum) or that of the office wall (painted gypsum board). Before the start of each experiment the offices were cleaned and ventilated at a high air exchange rate for 48 hrs, while the material samples were ventilated for 48 hrs under high air exchange rate conditions in separate locations. The sensory panel assessed the air quality of the offices using a continuous acceptability scale (see Figure 1). Sensory evaluations were first performed for the empty rooms and then, after moving the materials into or out of the rooms, depending on the design of each experiment (see Table 1). Sensory assessments were performed according to a randomized plan that was different for different subjects and different days of the experiments. During the experiments, the evaluated building materials were placed behind a screen in each room; hence, the subjects were unaware of the experimental conditions in a given room.