• 환경위생공학
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• 제14권4호
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• pp.85-92
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• 1999

Indoor air quality tends to be the dominant contributor to personal exposure because most people spend over 90% of their time indoors. For some contaminants, exposure to indoor air poses a potentially greater health threat than outdoor air exposures. Indoor nitrogen dioxide ($NO_2$) levels are mainly affected gas range, flue gas spillage, kerosene heaters, wood-burning appliances and cigarette smoke. In addition, indoor $NO_2$ levels are influenced by such house characterization as surface reaction and air exchange rate. In this study, the measurements of indoor and outdoor $NO_2$ concentrations were taken using identical protocols, and information was collected on housing characteristics using identical questionnaires in 14 houses out of 15 houses for daily 30 daily 30 days in Brisbane, Australia.The usage of gas range was the most contributing factor in indoor $NO_2$ concentration in relation to house characteristics. Average indoor and outdoor ratios of NO2 concentration in electronic and gas cooking houses were $0.6{\pm}0.1$ and $0.9{\pm}0.2$, respectively. The frequency distributions of $NO_2$ concentration in each house were approximately log-normal Geometric mean of indoor $NO_2$ concentrations of electronic and gas cooking houses for daily 30 days ranged from 2.5 ppm to 11.5 ppm with a mean 6.8 and from 4.7 ppm to 28.6 ppm with a mean 15.6 ppm, respectively. The $NO_2$ concentrations between electronic and gas cooking houses were significantly different (p<0.05). Since each house has different life-style and house characteristics, sampling interval to measure the $NO_2$ levels was recommended above 7 days.

• 한국환경보건학회지
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• 제30권3호
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• pp.259-263
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• 2004

This study was performed to investigate airborne formaldehyde concentration in preschool facilities. Arithmetic mean of indoor formaldehyde concentration in urban area was 34.9 ppb(Geometric mean 24.4 ppb) whereas outdoor concentration was 21.5 ppb(GM 11.9 ppb). In rural area, formaldehyde concentrations were 36.4 ppb(GM 28.7 ppb), 4.1 ppb(GM 4.1 ppb), respectively. There is no statistical significance between the formaldehyde concentrations of urban classrooms and those of rural area. We verified that the distribution of airborne formaldehyde concentration was log-normal characteristic using Shapiro and Wilk test. The 6.7% of urban indoor samples was exceeded the domestic standard limit of indoor air quality. From our study and other study, we concluded that the major emission sources of formaldehyde in preschool facilities was in indoor rather than outdoor.

• 한국환경과학회지
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• 제24권10호
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• pp.1273-1283
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• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• 한국환경보건학회지
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• 제35권1호
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• pp.11-20
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• 2009

This study was conducted in industrial area. The level of nitrogen dioxide was measured indoor, outdoor, work and personal in an study area within 5 km from source of pollution and control area 15 km farther from August, 2006 to September. The followings are the summary of this research. The concentration of the indoor and the outdoor $NO_2$ levels in the industrial area are 18.41$\pm$6.35 ppb, 18.51$\pm$3.26 ppb each, and the indoor/outdoor concentration rate is 0.99. The concentration of $NO_2$ in the workplace is 18.59$\pm$10.16 ppb, and the individual exposure rate is 18.80$\pm$5.71 ppb. The concentration of the indoor and the outdoor $NO_2$ levels control area are 12.57$\pm$3.82 ppb, 9.68$\pm$2.16 ppb each, and the indoor/outdoor concentration rate is 1.33. The personal exposure rate is 14.49$\pm$10.06 ppb. The residents of the each area and those of the comparative area spend 80.9% and 76.9% each their time in the indoor. It shows they spend most of their time in indoor. The predictions of the individual exposure rates in the industrial area and the comparative area are 15.10$\pm$6.14 ppb and 10.52$\pm$3.82 ppb each, The concentration levels measured by passive sampler are 18.80$\pm$5.71 ppb and 14.49$\pm$10.34 ppb each. The result of the research is the analysis of the personal exposure rate in indoor, outdoor and workplace of industrial area. This research may bo used as a basic data to manage and to establish the plan for $NO_2$ gas of the industrial area.

• Architectural research
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• 제8권1호
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• pp.37-45
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• 2006

A fungal spore transportation model that accounts for the concentration of airborne indoor spores and the amount of spores deposited on interior surfaces has been developed by extending the current aerosol model. This model is intended to be used for a building with a mechanical ventilation system, and considers HVAC filter efficiency and ventilation rate. The model also includes a surface-cleaning efficiency and frequency that removes a portion of spores deposited on surfaces. The developed model predicts indoor fungal spore concentration and provides an indoor/outdoor ratio that may increase or decrease mold growth risks in real, in-use building cases. To get a more useful outcome from the model simulation, an uncertainty analysis has been conducted in a real building case. By including uncertainties associated with the parameters in the spore transportation model, the simulation results provide probable ranges of indoor concentration and indoor/outdoor ratio. This paper describes the uncertainty quantification of each parameter that is specific to fungal spores, and uncertainty propagation using an appropriate statistical technique. The outcome of the uncertainty analysis showed an agreement with the results from the field measurement with air sampling in a real building.

• 환경위생공학
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• 제12권3호
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• pp.51-59
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• 1997

In this study, we researched the concentration of nitrogen dioxide($NO_{2}$) and sulfur dioxide($SO_{2}$) of indoor(waiting room) and outdoor(place of getting on the bus) at the bus terminals (Kang-Nam, Dong-Seoul and Nam-Bu) in Seoul to recognize the degree of pollution by exhaust gas of the diesel engine vehicles, and examine the factor that might affect air pollution of terminals. The concentration of $NO_{2}$ and $SO_{2}$ were measured in winter and summer, and the results of the analysis are as follows : The mean concentration of $NO_{2}$ was $57.49{\pm}21.86$ ppb and the concentration of outdoor with $64.10{\pm}27.69$ ppb was significantly higher than the indoor with $50.89{\pm}10.92$ ppb (p<0.05), and the highest with $73.54{\pm}25.54$ ppb at Kang-Nam terminal (p<0.01). The mean concentration of $NO_{2}$ was $62.80{\pm}24.74$ ppb in winter and $52.19{\pm}17.50$ ppb in summer, and had a not statistical difference. The mean concentration of $SO_{2}$ was $31.71{\pm}8.73$ ppb and the concentration of outdoor with $31.04{\pm}8.89$ ppb was similar to the indoor $32.29{\pm}8.70$ ppb, and the highest with $32.57{\pm}9.01$ ppb at Dong-Seoul terminal (p<0.05). The mean concentration of $SO_{2}$ in winter with $39.67{\pm}4.10$ ppb was significantly higher than in summer with $23.76{\pm}2.61$ ppb (p<0.01). The concentration of outdoor $NO_{2}$ at Kang-Nam terminal was 104, 84 ppb in winter and 81.20 ppb in summer, and had a statistical difference compared with the concentration of indoor $NO_{2}$ at Dong-Seoul and Nam-Bu terminals. The concentration of indoor $NO_{2}$ and $SO_{2}$ were higher than that of outdoor at Kang-Nam and Dong-Seoul terminals, but on the contrary, lower than that of outdoor at Nam-Bu terminal. The concentration of $NO_{2}$ and $SO_{2}$ at Nam-Bu terminal were lower than those at Kang-Nam and Dong-Seoul terminals. While the concentration of $SO_{2}$ show the large difference between winter and summer, that of $NO_{2}$ dose not.

• Advances in environmental research
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• 제2권1호
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• pp.61-80
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• 2013

Quantification of viable forms of microbial community (bacteria and fungi) using culture-dependent methods was done in order to characterize the indoor air quality (IAQ). Role of those factors, which may influence the concentration of viable counts of bacteria and fungi, like ventilation, occupancy, outdoor concentration and environmental parameters (temperature and relative humidity) were also determined. Volumetric-infiltration sampling technique was employed to collect air samples both inside and outside the schools. As regard of measurements of airborne viable culturable microflora of schools during one academic year, the level of TVMCs in school buildings was ranged between 803-5368 cfu/$m^3$. Viable counts of bacteria (VBCs) were constituted 63.7% of the mean total viable microbial counts where as viable counts of fungi (VFCs) formed 36.3% of the total. Mean a total viable microbial count (TVMCs) in three schools was 2491 cfu/$m^3$. Outdoor level of TVMCs was varied from 736-5855 cfu/$m^3$. Maximum and minimum VBCs were 3678-286 cfu/m3 respectively. Culturable fungal counts were ranged from 268-2089 cfu/$m^3$ in three schools. Significant positive correlation (p < 0.01) was indicated that indoor concentration of viable community reliant upon outdoor concentration. Temperature seemed to have a large effect (p < 0.05, p < 0.01) on the concentration of viable culturable microbial community rather than relative humidity. Consistent with the analysis and findings, the concentration of viable cultural counts of bacteria and fungi found indoors, were of several orders of magnitude, depending upon the potential of local, spatial and temporal factors, IO ratio appeared as a crucial indicator to identify the source of microbial contaminants.

• 한국환경보건학회지
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• 제46권5호
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• pp.504-512
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• 2020

Objective: The purpose of this study was to evaluate the indoor to outdoor ratio (I/O ratio) of time activity patterns affecting PM_2.5 concentrations in homes in Korea through a simulation. Methods: The time activity patterns of homemakers were analyzed based on the 'Time-Use Survey' data of the National Statistical Office in 2014. From September 30 to October 2, 2019, the experimenter lived in multifamily housing located in Guro-gu, Seoul. The I/O ratio of PM_2.5 concentration was measured by installing sensor-based instruments. Results: The average indoor and outdoor PM_2.5 concentrations during the three days were 33.1±48.9 and 45.9±25.3 ㎍/㎥, respectively. The average I/O ratio was 0.75±0.60. The indoor concentration tended to increase when PM_2.5 source activity such cooking and cleaning was present and outdoor PM_2.5 was supplied through ventilation. Conclusions: This study could be used as basic data for estimating indoor PM_2.5 concentrations with personal activity pattern and weather conditions using outdoor concentrations.

• 한국환경보건학회지
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• 제34권2호
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• pp.137-147
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• 2008

This study evaluated the effects of the human activity and outdoor air on concentrations of size-selective particulate matters (PM) by conducting a realtime measurement in classrooms and on roofs at 4 elementary schools, 3 middle schools and 3 high schools in Incheon City. PM concentrations featured repetitive pattern of increasing during break time (including lunch hours) and cleaning time while decreasing during class hours. This trend was more prominent with inhalable PM and PM10 than fine PMs (PM2.5, PM1.0). The indoor/outdoor (I/O) ratio of inhalable PM and PM10 exceeded 1 while that of fine PMs was close to or below 1. The PM2.5 (out)/PM10 (out) ratio stood at 0.59 (${\pm}0.16$) and the PM2.5 (in)/PM10 (in) ratio was 0.29 (${\pm}0.09$), suggesting that occupant activity had a greater effect upon coarse particles (PM10-PM2.5) than upon fine particles (PM2.5, PM1.0). The correlations between the indoor and the outdoor PM concentrations showed a stronger positive correlation for fine particles than that of coarse particles. The linear regression analysis of PM concentrations indoor and outdoor indicated a higher determinant coefficient ($r^2>0.9$), and consistency for fine particles than in case of coarse particles. In conclusion, the results of this study suggest that the indoor coarse particle concentration is more attributed to occupant activity and the indoor fine particle concentration is more influenced by outdoor air pollution.

• 한국환경보건학회지
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• 제22권4호
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• pp.43-48
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• 1996

Indoor air quality(IAQ) in museum is very important for protection of cultural properties. In our study, we measured air pollutants($NO_x, NH_3, SO_2, O_3$, CO, $CO_2$, TSP), temperature and humidity to evaluate IAQ of national central museum. Indoor carbon dioxide and TSP concentrations were higher than outdoor concentrations. Temperature, huinidity and TSP had large deviation depending on air conditioning operates or not. Indoor gas phase pollutants except $CO_2$ were lower than outdoor concentrations, but $SO_2$ concentration was high in storage. $CO_2$ and TSP were influenced by the number of spectators.