The Study Of Changes Of Indoor Ozone Concentrations And Sources Of Indoor Ozone

As the pollution of Photochemical smog arose, a large amount of research, whichfocused on the relationship between indoor and outdoor ozone concentrations, havebeen carried out by foreign researchers since the early 1970s, whereas few researcheson such topics has been found in our nation except for Hong Kong. The object of thisthesis is to bridge the gap of knowledge and provide a reference for people who wantto avoid personal ozone exposure and improve indoor air quality. There are two mainparts in this thesis. The first one is to monitor the changes of indoor and outdoorozone concentrations and investigate the indoor-outdoor ozone concentration ratio.Using ultraviolet adsorption method, we have carried out consecutive measurementon some representative buildings, which include two office rooms, one residentialbedroom, two classrooms in a middle school and one cleanroom in a Pharmaceuticalmanufactory. The results of the investigation indicate that the change of indoor ozonelevels is similar to that of outdoor. On cloudless days the ozone levels tend to rise inthe morning, to be highest at noon or in the afternoon and then decline. Ozoneconcentrations most likely peak during 14:00-16:00 pm. Lags between peaks ofoutdoor concentrations and subsequent indoor peaks have been observed during theinvestigation. The respective lag time is 4 hours for an office and 1 hour for aclassroom. The average indoor values were 9.5 to 84.5 percent of those outdoors, andare closely related to air exchange rates. Another objective of this thesis is to find outthe main factors influencing the ozone emission rate of electrostatic air filters. Byusing a stainless steel test plenum, we have measured the ozone emission rates underdifferent voltage levels, air flow rates, and figurations of corona electrode. Themeasured ozone emission rates are 10.6-225.6 mg/m3. The voltage level andfiguration of corona electrode are found to be the main factors influencing ozoneemissions. The higher the voltage of corona electrode is, the more ozone will beproduced if other factors remain invariable. Filters with a flat corona electrode tend toproduce more ozone than those with a wire corona electrode. In addition, theinfluence of temperature and the air flow pattern on ozone deposition on indoorsurfaces has been checked in the present study. The results suggest that the air flowpattern affects the ozone deposition rate greatly, while a small change of temperaturewould not be so important. Furthermore, this thesis also discussed the methodseffective for reducing indoor ozone concentrations from the point view of theory.