Development of a Novel Methodology for the Identification of VOC Emission Sources in Indoor Environments based on the Material Emission Signatures and Air Samples measured by PTR-MS

One of the recent important challenges in the research field of ind or air quality is the identification of indoor Volatile Organic Compound (VOC) emission sourc es to clearly pinpoint the sources of concern in a field condition. This study repres nts the first attempt in developing a new technique to find the sources that may be invisible or hidden based on the inspection even of experts when a building with problems of indoor air quality is suspected. The objectives of this study were 1) to dete rmine VOC emission signatures specific to nine typical building materials by usin g a on-line analytical monitoring device, Proton Transfer Reaction Mass Spectrometry ( PTR-MS), 2) to explore the correlation between the PTR-MS measurements and the m easurements of acceptability by human subjects, 3) to develop and evaluate a methodology t identify individual sources of VOC emissions based on the measurements of mixe d air samples and the PTR-MS material emission signatures, 4) to determine the long-term variation of VOC emission signatures over time, and 5) to develop a method to acc ount for the longterm variation of emission signatures in the application of the emi ssion source identification method. Samples of nine building materials were te st d individually and in combination, including carpet, ceiling material, gypsum board, linole um, two paints, polyolefine, PVC and wood. VOC emissions from each material we re measured in a 50liter small-scale chamber. Chamber air was sampled by PT R-MS to establish a database of emission signatures unique to each individual material. Sorbent tube sampling and TD-GC/MS analysis were also performed to identify the major V OCs emitted and to compare the resulting data with the PTR-MS emission signatur es. The data on the acceptability of air quality assessed by human subjects were obt ained from a previous experimental study in which the emissions from the same batch o f materials were determined under the same area-specific ventilation rates as in the case of the current measurements with PTR-MS. The same task was performed to measure combined emissions from material mixtures for the application and validat ion of a signal separation methodology and its source identification enhancement by the considera tion of long-term emissions. The methodology was developed based on signal processing principles by employing the method of multiple regression least squares (MRLS ) and a normalization technique. Source models were employed to track the change of indivi dual material emission signatures by PTR-MS over a long period of time. It is concluded that: 1) PTRMS can be an effective tool for establishing VOC emission sig atures of material types, and there were sufficient correlations (i.e. Correlation coeffi ci nt r < -0.92 ) between the PTR-MS measurements and the acceptability of air quality for the nine materials tested when the sum of selected major individual VOC odor indices was used t o represent the emission level measured by PTR-MS; 2) the proposed method for sour ce identification could identify the individual sources at high success rates under la boratory conditions with two, three, five and seven materials present; and 3) the lon g-term (over nine months) variation of emission factors of the tested materials could be we ll represented by an empirical power-law model or a mechanistic diffusion based model, a nd the model coefficients could be estimated based on relatively a short-te rm set of emission measurements (i.e. ≤ 28 days). The source models could also be used to predict the variation of material emission signatures, which could in turn be us ed for source identification. Further experiments and investigation are needed to apply the presented source identification method under real field conditions. Development of a Novel Methodology for the Identification of VOC Emission Sources in I ndoor Environments based on the Material Emission Signatures and Air S amples measured by PTR-MS By Kwanghoon Han BS, at Seoul National University, 1999 MS, at Seoul National University, 2001 DISSERTATION Submitted as the partial fulfillment of requirements for the Degree of Doctor of Philosophy in Mechanical and Aerospace Engineering of the Graduate School at Syracuse University May 2011 Advisor: Jensen S. Zhang, Ph.D Copyright © 2011 Kwanghoon Han All rights are reserved. Should be used by permission. Ph.D Dissertation Kwanghoon Han (한광훈) VI Development of a novel methodology for the identification of VOC emission sources in indoor environments TABLE OF CONTENTS ABSTRACT . VI ACKNOWLEGEMENTS . XVI † CHAPTER