Numerical analysis was conducted to characterize the particle charging quantities in the charging cell of a 2-stage parallel-plate electrostatic precipitator with respect to particle size. The numerical method took into consideration of particle charging rate equations and particle equations of motion, allowing the locally varying non-uniform electric field and ion number concentration along the particle trajectory. The charging rate model developed by Lawless (1996) was used in the present study. According to the present study, the numerical results showed good agreement with the available experimental data.

This study was performed to investigate the concentration levels of CO2 and the associated parameters in the subway from lines 1 to 8 in Seoul metropolitan area, during 1 to 30 Sept. 2005. CO2 concentration was measured at the entrance and center in subway passenger cabin by non-dispersive infrared analyser. The associated parameters for CO2 were estimated based on the number of passenger, open and closed doors etc. The mean CO2 concentrations were measured to be 1,646±712 ppm in subway passenger cabins. The CO2 concentrations showed the highest values between 7 and 9 AM in rush hour(p〈0.01). The correlation coefficient between CO2 and the number of passenger was highly significant(r=0.824). The general linear model indicated that subway line, subway location (ground and underground tract), and measurement point (enterance and center of cabins) and running time (morning and afternoon) significantly influenced the concentrations of CO2. An extended study is needed to examine the sources of CO2 in subway cabins and to compare pollutants concentration among subway lines.

Indoor air quality tends to be the dominant contributor to personal exposure, because most people spend over 80% of their time indoors. In this study, indoor and outdoor NO2 concentrations were measured simultaneously with personal exposures of 30 university students in weekday and weekend in Daegu, Korea. House characteristics and subject's activity pattern were used to determine the effects on personal exposure. Since university students spent most of their times indoor, their NO2 exposure was associated with indoor NO2 level during both weekday and weekend in spite of different time activity. Using a time-weighted average model, NO2 exposures of university students were estimated by NO2 measurements in indoor home, indoor school, and outdoor home. In conclusion, major personal exposure to NO2 resulted from air quality of indoor environment at house.

In this paper, exposure levels of electromagnetic field were measured in residential environments and from appliances. First, the measurements of residential environments were taken in central locations in bedroom, living room, and kitchen in each home. Both arithmetic and geometric mean of normal-power condition are higher than low-power condition (all electrical devices turned off/unplugged), and the background fields in homes show a geometric mean of about 0.022 uT. Second, we measured broadband magnetic fields of domestic appliances at various distances. The highest magnetic field is 44.3 uT from the microwave oven, and the lowest is 1.4 uT from the Kimchi Refrigerator. The magnitude of magnetic fields from appliances dropped off at a rate inversely proportional to distance, but the ratio of drop-off on Korean appliances is lower than US and UK

teacher s efficiency is an important factor. Recently, some schools installed an air conditioner in classroom, while most schools selected the built-in type air conditioner. However, the study on a valuation of thermal environment is not sufficient, especially in classroom. It is insufficient that the study is a valuation of thermal environment which considered valuation about indoor thermal environment diffusion angle and air volume. In this work, the change of thermal environment was investigated for five kinds of air diffusion angle(15∘, 30∘, 45∘, 60∘, 90∘) for ceiling type air conditioner. The vector and temperature distributions of air in the room were calculated by a 3-dimensional numerical method. This study was also conducted to calculate the Mean Age of Air and Predicted Mean Vote(PMV). This analysis showed that 30-45° is the optimum angle of diffusion in cooling mode and in heating mode.

We surveyed the concentrations of PM10, O3, and bioaerosol in public facilities including restaurants, offices, and private academies in Chung-Nam province area. During 3 months (from August 30, 2005), the bioaerosol concentrations were measured by a single stage air cascade sampler using the inertia collision catching method for the flux of 28.29 ℓ/min. The mean values were measured as 101.1㎍/㎥ for PM10 and 12.4 ppb for O3. The concentrations of colony for bacteria and fungi were 464 and 287 CFU/㎥ in restaurants, 223 and 271 CFU/㎥ in offices, and 259 and 107 CFU/㎥ in private academics. It is thus suggested that the regulation of indoor air conditions should be amended to control the quantity of bioaerosol in public facilities.

Recently, indoor air quality (IAQ) in workplace, residence, and schools has been one of the major concerns of people, scientists and the related public. This study was performed to investigate the characteristics of indoor air quality(IAQ) in kindergartens, elementary school, middle schools, and high schools from June 2004 to May 2005 in Korea. We measured indoor air pollutants such as PM10, CO2, formaldehyde, total bacteria colony(TBC), CO, radon, total volatile organic compounds(TVOCs), asbestos, and O3 from school classrooms. The subjects were classified by building year based on the time span of 1, 1 - 3, 3 - 5, and 5 - 10 years. The levels of pollutants and physical factor in schools were compared with standards and guidelines of indoor air quality on the Ministry of Environment, the Ministry of Health and Welfare, and the Ministry of Education, and Human Resources Development of Korea. The major results obtained from this study can be summarized as follows. Asbestos and O3 were not detected in all surveyed classrooms. However, we were able to detect CO, TBC, TVOCs, and formaldehyde in kindergartens, TBC in elementary schools, TBC, TVOCs and formaldehyde in middle schools, and formaldehyde in high schools. This study was conducted to provide a basis for the management IAQ in school. Therefore, we suggest that a national plan for the management of IAQ in school should be established through a long-term, continuous investigation for the proper assessment of IAQ in school and for the health risk assessment for student.