• Journal of environmental and Sanitary engineering
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• v.14 no.4
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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.

• Journal of environmental and Sanitary engineering
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• v.17 no.2
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• pp.85-91
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• 2002

Workers who work at indoor and outdoor environment near busy road are suspected to be exposed to high-elevated air pollutant levels during working hours. This study evaluated the working-time nitrogen dioxide ($NO_2$) exposure for workers (repairmen and polishers) of shoe-stalls. Since shoe-stalls have particularly been located near busy road in Korea, workers might be high exposure to $NO_2$ from traffic exhaust as well as indoor sources of shoe-stall such as portable gas range (butane gas) during working hours. In this study, we measured the indoor and outdoor $NO_2$ concentrations of shoe-stalls. Simultaneously, outdoor $NO_2$ concentrations of building through sidewalk from shoe-stall were measured. High $NO_2$ exposure for workers of shoe-stalls was considered to be inflow of outdoor source of exhausted emission from vehicles and indoor source from usage of gas range to polish the shoe. Indoor/outdoor $NO_2$ concentration ratio ($0.94{\pm}0.22$) in Seoul was higher than that ($1.06{\pm}0.34$) in Asan, because ambient $NO_2$ level was high in Seoul and usage of gas range was prevalent in Asan. According to $NO_2$ concentrations by distance from roadside to building through sidewalk, $NO_2$ concentrations showed the decreased trend with distance. The results of this study can be utilized by municipal authorities in urban planning for evaluating effects of future traffic planning and land use.

• Journal of Environmental Health Sciences
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• v.36 no.5
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• pp.351-359
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• 2010

The objectives of this study were to understand the characteristics of residents in industrial areas and factors affecting exposure to the Volatile Organic Compounds(VOCs : Benzene, Toluene, Xylene) as well as to assess exposure levels according to house-type, and whether residents were indoors or outdoors. This research was designed to assess the differences in exposure levels to indoor, outdoor and personal VOCs in a case group and a control group across all areas, as well as in each different area, from May to October 2007, in. 110 residents of the G, Y and H industrial areas of the Jun-nam province. The geometric mea-levels of airborne benzene for the case group 1.31part per billion(ppb) indoor, 1.29 ppb outdoor, and 1.32 ppb for personal exposure were significantly higher than for the control group 0.99, 0.87 and 0.57 ppb, respectively. The geometric mean level for toluene personal exposure across the G, Y and H areas was 5.70 ppb for the case group and 6.31 ppb for the control group. While the outdoor level was 4.27 ppb for the case group and 5.06 ppb for the control group, The indoor level for the case group was 4.78 ppb, similar to that of the control group 4.69 ppb. The geometric mean levels for airborne xylene across the G, Y and H areas were 0.16 ppb(outdoor), 0.12 ppb(personal exposure) and 0.10 ppb(indoor) for the case group, and for the control group were 0.17(personal exposure) and 0.09 ppb(indoor and outdoor). The indoor/outdoor(I/O) ratio for case group is 1.19, while that of the control group is 1.15, indicating that the indoor level was higher than the outdoor level. The interrelationship differences among the three different types of levels in the air in the G, Y and H areas are statistically significant, except for the difference between the indoor and outdoor figures for xylene. In terms of the different types of houses and energy type uesd, the geometric mean level for airborne benzene, toluene and xylene for houses were 1.61, 5.39 and 0.12 ppb, respectively. while the figures for flats were 0.67, 3.32 and 0.05 ppb, respectively. Outdoors, the levels of benzene and toluene in flats were 0.71 and 2.62 ppb, respectively. and 1.58 and 5.35 ppb in houses. For personal exposure, the house levels of benzene, toluene and xylene were all higher than for flats. Houses using oil for heating have significantly higher levels than flats, which use gas for heating.

• Advances in environmental research
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• v.2 no.1
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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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.355-363
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• 2005

This paper is discussed about the technology of the performance enhancement in the wireless communication between indoor and outdoor environments. In the outdoor wireless communication, the signal has mainly a severe degradation by the fading effect of channel, but that problem may be overcome by using ordinary multiple antenna technology and array signal processing algorithm. Hence, since the channel has the characteristics of both fading and angle spread in the wireless communication between indoor and outdoor, the ordinary technology cannot solve the signal degradation due to the angle spread. In order to solve the problem, in this paper, the characteristic of the wireless channel between indoor and outdoor is first analyzed and considered the channel models fit to that case. We propose the new multiple antenna algorithm by use of mean steering vector concept, and obtained the results of the performance enhancement. With the results of the performance analyses through of the numerical study and computer simulation, we show that the proposed algorithm has more enhanced signal to noise ratio than the previous algorithm.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.1
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• pp.61-68
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• 2018

Recently, concentration of fine and ultra-fine particulate matter(PM) has been increased in KOREA. The increase of PM in KOREA is due to increase of domestic industries and yellow dust from china. PM is known to cause diseases such as dyspnoea, asthma, arrhythmia. Since PM is harmful to human, KOREA Ministry of Environment(ME) warns people to stay indoors when the outdoor PM concentration is high. However, prior studies has shown that indoor PM concentration can be relatively high when outdoor PM concentration is high due to infiltration of PM into buildings though leakage areas. In this study, airtightness, indoor and outdoor pressure difference and PM 2.5 & 10 concentration were measured in an apartment complex to observe PM infiltrating into building. Field measurement was conducted in newly-built apartment buildings to avoid the influence of indoor PM which can be generated by residents. The airtightness test was conducted to identify the leakage areas of the apartment, such as electric outlets and supply/exhaust diffusers. The airtightness test result showed that the air leakage area of the building was dominant in buildings envelop. According to indoor and outdoor pressure difference measurement result and PM concentration measurement result, it can be concluded that outdoor PM can infiltrate into indoor by leakage areas when wind is blown toward the apartment. As a result, pressure difference formed by the external weather condition and architectural characteristics such as the airtightness in building can influence PM to infiltrate into buildings. In further studies, I/O ratio, stack-effect, infiltration and penetration factor will be considered.

• Journal of Engineering Education Research
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• v.13 no.5
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• pp.76-80
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• 2010

In this paper, the Location Compensation Mechanism using equivalent distance rate ($LCM_{edr}$) for localization system based on SDS-TWR (Symmetric Double-Sided Two-Way Ranging) in wireless sensor network is proposed. The performance of the mechanism is experimented in terms of two types of the localization tracking scenarios of indoor and outdoor environments in university campus. From the experimentations, the compensation ratio in the $LCM_{edr}$ is better than that in SDS-TWR about 90% in indoor/outdoor environments in scenario 1 but also is better than that of SDS-TWR about 91.7% in indoor environment and about 100% in outdoor environment in scenario 2 respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1165-1173
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• 2001

The objectives of this study are to analyze the application of radiant floor cooling and to evaluate the control methods through experiments when the radiant heating system is used for cooling. Through the experiment analysis the control methods such as on/off control, variable flow control and outdoor reset with indoor temperature feedback control are evaluated and compared. The cooling curve (reset ratio) is found for radiant cooling, which shows tole relation between outside air temperature and supply water temperature. Comparison of cooling methods shows that outdoor reset with indoor temperature feedback control is more appropriate than on/off control and variable flow control with regard to prevention of the condensation and thermal comfort.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.10
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• pp.891-897
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• 2005

The characteristics of energy Performance for total heat exchanger have been investigated under various conditions. In cooling operation the latent and enthalpy efficiency are affected by the difference of absolute humidity ratio between indoor and outdoor air. In addition to this the characteristics of absorbing material in the element affects the energy performance. Low dry bulb temperature of indoor air or high absolute humidity ratio in outdoor air give high latent and enthalpy efficiency even with the same temperature difference of dry bulb temperate between indoor and outdoor air.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1325-1331
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• 2007

In order to investigate the cooling capacity of an air-conditioner applying a variable capacity compressor and the temperature characteristics on a condenser and an evaporator, the experiment on the operation characteristics of the air-conditioner was performed along a compressor operation ratio and an indoor/outdoor temperatures, under a cooling operation mode. The system characteristics were measured by the psychrometric calorimeter. The cooling capacity increased with decreasing the outdoor temperature and increasing the indoor temperature. Also, it increased with increasing the compressor operation ratio. The temperature of the condenser was more sensitive for the variation of the outdoor temperature and the temperature of the evaporator was more sensitive for the variation of the indoor temperature. The operation characteristics of the cycle used in this present were also analyzed by a pressure-enthalpy chart.