• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1622-1628
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• 2007

We characterized the efficacy of an electrostatic precipitator (ESP) air-cleaner in reducing the concentration of Serratia marcescens in an enclosed space. We used an experimental room ($4.5{\times}3{\times}2.9\;m$) in which electrostatic air-cleaners were located. Two air-cleaners enhanced the equivalent ventilation rates in the chamber by about 3.3 air changes per hour (ACH) over the 2 ACH provided by the mechanical ventilation system. Natural die-off of the organisms provided an additional equivalent of 3 ACH, so that the total ventilation rate with the ESP air-ccleaners was 8.3 ACH. We also examined whether the ESP air-cleaners altered the deposition of Serratia marcescens aerosols on the experimental room surfaces. We did not find any significant differences in the number of colony forming units recovered from surfaces with and without the air-cleaners. We installed UV lights inside the ESPs and determined if UV light, in addition to electrical fields, increased the efficacy of the ESPs. The presence of UV light inside the ESP reduced S. marcescens aerosols by approximately 2 ACH. Finally, a box model indicates that the efficiency of the air-cleaner increases for both biological and nonbiological particles at ventilation rates of 0.2-1, which are typical for residential settings.

• Journal of The Korea Institute of Healthcare Architecture
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• v.20 no.1
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• pp.7-14
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• 2014

Purpose: In this study, we performed ventilation simulations for a standard isolation ward including three intensive care rooms, one anteroom(buffer room), and its recommended ventilation equipments. The purpose of this study is to predict outflow of pathogenic bacteria from patient breath to verify the reliability and the safety of the isolation ward. Methods: We suppose three scenarios of the movement of medical staff. The leakage of patient's breath to out of the ward is predicted in these scenarios using CFD simulations. Results: The patient's breath leakage rate to out of the ward in scenario 1 according to room air changes per hour(ACH : 6 and 12) is predicted to be 0.000057% and 0.00002%, respectively. The patient's breath leakage rate to out of the ward in scenario 2 according to room air changes(ACH : 6 and 12) is predicted to be 0.00063% and 0.00019%, respectively. The patient's breath leakage rate to out of the ward in scenario 3, which is the worst case(6 room air changes) is predicted to be 0.1%. Implications: Through the ventilation simulation like that in this study, the reliability and the safety on isolation performance of various plan of isolation ward are predicted quantitatively.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1286-1295
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• 2000

The ventilation effectiveness is evaluated as a function of air exchange rate and supply / extract locations in a simplified model chamber using a tracer gas technique of CO$_2$ gas injected into a supply duct. Ventilation systems consist of supply and extract fans, a CO$_2$gas generator, a CO$_2$gas analyzer and a test chamber. The ventilation effectiveness is evaluated using a step-down method based on ASTM Standard E741-83. The room mean age of the model chamber is decreased with increasing air exchange rate fanged from 6to 10 air changes per hour. The ventilation effectiveness of the mechanical inlet/natural extract system is better than that of the mechanical extract system.

• Journal of Environmental Science International
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• v.23 no.2
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• pp.207-218
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• 2014

A ventilation model was developed for predicting the air change per hour(ACH) in buildings and the airflow rates between zones of a multi-room building. In this model, the important parameters used in the calculation of airflow are wind velocity, wind direction, terrain effect, shielding effect by surrounding buildings, the effect of the window type and insect screening, etc. Also, the resulting set of mass balance equations required for the process of calculation of airflow rates are solved using a Conte-De Boor method. When this model was applied to the building which had been tested by Chandra et al.(1983), the comparison of predicted results by this study with measured results by Chandra et al. indicated that their variations were within -10%~+12%. Also, this model was applied to a building with five zones. As a result, when the wind velocity and direction did not change, terrain characteristics influenced the largest and window types influenced the least on building ventilation among terrain characteristics, local shieldings, and window types. Except for easterly and westerly winds, the ACH increased depending on wind velocity. The wind direction had influence on the airflow rates and directions through openings in building. Thus, this model can be available for predicting the airflow rates within buildings, and the results of this study can be useful for the quantification of airflow that is essential to the research of indoor air quality(temperature, humidity, or contaminant concentration) as well as to the design of building with high energy efficiency.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.167-168
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• 2023

The government has established a zero-energy roadmap in accordance with its 2050 carbon neutrality strategy, and from 2023 onwards, residential buildings with 30 generations or more must be constructed as zero-energy structures. In response to this, measures for energy conservation through enhanced building tightness are being developed. The LH (Land and Housing Corporation) aims to achieve the first-stage building tightness performance targets by 2022 in preparation for this. Currently, South Korea has the "KS L ISO9972 - Building Tightness - Measuring the airtightness of buildings by the fan pressurization method" as the method for measuring building tightness, which was established in 2006 and revised in 2016. In practice, the airtightness is measured using the Blower Door Test method, and it is expressed as ACH50 (the number of air changes per hour at a pressure difference of 50 Pa between the indoor and outdoor environments). This study aims to measure and analyze the airtightness of Happy Homes constructed from 2020 to 2022, categorized by building type.

• Land and Housing Review
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• v.13 no.3
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• pp.93-106
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• 2022

Ventilation plays an important role in controlling indoor air quality. Due to the recent spread of infectious diseases such as COVID-19 and with people spending more time indoors, there's been increased attention on the importance of ventilation performance. In many countries, ventilation is regulated by airflow rates and the number of air changes per hour (ACH). However, airflow rates and ACH alone do not provide an accurate account of actual indoor pollutant removal and ventilation uniformity in a space. This study looked into the ventilation performance of an actual residential unit using several sampling points instead of basing it off of airflow and air change rates. Literature review was used to derive relevant influencing factors and the tracer gas dilution method was used for the field test. The study measured air velocity, age of air, and ventilation efficiency at several locations and compared them to the average value at the center of the test space to determine the differences in ventilation performance at the selected measurement points. The study showed that different sampling locations resulted in different ventilation values. Findings of this study will be used to develop an experimental procedure for evaluating indoor ventilation performance of actual residential spaces.

• Land and Housing Review
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• v.14 no.4
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• pp.111-120
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• 2023

Indoor air quality has become increasingly important with the increase in time spent in residential environments, impact of external fine dust, yellow dust, and the post-COVID 19 pandemic. Residential mechanical ventilation plays a key role in addressing indoor air quality. The legal standard for residential air changes per hour in Korea is 0.5 ACH. However, there are no standards for the location of supply and return vents. This study atempts to analyze the impact of ventilation performance based on the location of supply and return vents. An experiment was conducted using the CO₂ tracer gas concentration decay method in a mock-up house set inside a large chamber to minimize external influences. The experimental results indicated that the commonly used combination of 2 supply and 2 return vents in living room spaces had a lower mean age of air than the combination of 1 supply and 2 return vents. Using multiple supply and return vents had lower mean age of air than using just 1 supply and 1 return vent.