High concentrations of fine particles are increasingly being detected due to inflows from abroad and local emission sources in Korea. As most people spend about 90% of their time indoors, the use of indoor air cleaners has grown significantly as they are now thought to be essential items. In this study, the noise, power consumption, and clean air delivery rate (CADR) of commercial air cleaners were analyzed according to the structural shape of the air cleaners. Analyses were performed based on the experimental results of 249 cases for air cleaners certified by Korea Air Cleaning Association. The air cleaners with front inlet and upper outlet air flow direction, which currently account for the highest market share, were found to have the highest noise per CADR (dB(A)/(m3/min)). On the other hand, the air cleaners with the inlet and outlet air flow in the same horizontal direction were found to have lowest noise per CADR than other structures.

Subway trains with air cleaners have been newly deployed in the Seoul Metro system. The purpose of this study was to determine differences regarding in-cabin particulate matter with respect to concentrations less than 10 um (PM10) and 2.5 um (PM2.5) through the operation of air cleaners in subway trains. One subway train newly installed with in-cabin air cleaners on Seoul Metro Line number 2 was chosen monitoring in 2020. In-cabin air cleaners were turned-on at both front and back areas while those in the middle area were turned-off while the train was running. In-cabin PM10 and PM2.5 concentrations were measured in each area using a real-time aerosol monitor. Average in-cabin PM10 concentrations were statistically significantly lower (by 15%) in areas with air cleaners turned-on (43.8±12.1 μg/m3) compared to those areas where the air cleaners were turned-off (51.4±15.0 μg/m3). Average incabin PM2.5 concentrations were significantly lower (by 14%) in areas with air cleaners turned on (33.7±12.2 μg/m3) compared to those areas where air cleaners were turned-off (39.2± 14.4 μg/m3). In-cabin PM10 and PM2.5 concentrations ratios were similar regardless of area with air cleaners turned-on or turned-off. The in-cabin PM10 and PM2.5 concentrations were not associated with commute time. Use of air cleaners in subway trains effected reductions in in-cabin PM10 and PM2.5 concentrations.

This study was undertaken to investigate whether HEPA filter-equipped air purifiers can remove aerosolized virus, whether the removed virus can re-scatter through the filter, and how long the removed virus keeps its infectivity in the filter. For this investigation, six HEPA filter-equipped air purifiers produced by different companies were tested against PhiX174 and MS2 phages aerosolized by nebulizers. For viral detection from the air, LB agar plates covered with Escherichia coli hosts and an Andersen air sampler were used, and from the surface, the swab method was used. Both the aerosolized PhiX174 and MS2 viruses absorbed by the HEPA filters in the air purifiers were not detected from the air through filters or the surface of the outlet of the air purifiers. During the operation of the air purifiers at medium mode, the infectious viral concentration of these viruses in the HEPA filters decreased to 0%~12.3% as the time period passed. These results regarding infectious viral concentration differences were assumed to be due to the different wind speed and air volume among the six air purifiers. Based on observations over 5 days, the infectious viral concentration of the PhiX174 phage was 8,600 times lower when the air purifier was operated than when it was not operated. Overall, our results demonstrate that HEPA filter-equipped air purifiers can efficiently remove the two aerosolized viruses and the removed viruses in the HEPA filter could not re-spread and maintain their infectivity.

High concentrations of PM2.5 were generated in new apartments before moving in, and PM2.5 reduction efficiencies using air cleaners and ventilation systems were evaluated. The experimental results for different air cleaner capacities showed that the PM2.5 reduction efficiencies for 46.2 m2, 66 m2, and 105.6 m2 areas were 81.7%, 92.9%, and 92.5%, respectively. Thus, the larger the air cleaning application area, the higher the PM2.5 reduction efficiency. However, there was no difference in the efficiency of overcapacity air cleaners above a certain capacity. The efficiencies of air cleaners located at the living room center, interior wall, and edge were 81.7%, 79.2%, and 75.8%, respectively. There was, therefore, no significant difference in the PM2.5 reduction efficiencies of air cleaners in different locations. Furthermore, the PM2.5 reduction efficiencies at distances of 1 m, 2 m, and 3 m were 81.7%, 81.3%, and 81.7%, respectively. Therefore, there was also no significant difference in efficiency with distance. The PM2.5 concentration decreases rapidly during natural ventilation. Therefore, when the indoor PM2.5 is higher than the outdoor PM2.5, the air cleaner should be used after natural ventilation. The efficiency of PM2.5 reduction using an air supply-type ventilation system in apartments was 35%, which is not high. The simultaneous operation of the ventilation system and kitchen range hood was effective, showing a PM2.5 reduction efficiency of 69.1%. However, a water sprayer was not effective, showing a PM2.5 reduction efficiency of 24.3%. The results of this study suggest that PM2.5 reduction performance should be standardized by evaluating the efficiency of different ventilation systems. Effective usage and maintenance standards for ventilation systems need to be disseminated, and ventilation systems and air cleaners should be used effectively.

Statistical analysis for the 703 air purifiers certified by Korea Air Cleaning Association from 2003 to 2019 was performed. Sixty-one percent of the products had an area coverage of 15 m2~30 m2 and the median value of the total products was 37.6 m2. The number of certified products by the top five manufacturers was 325, which corresponds to 46.2% of the total products. The median value of the clean air delivery rate (CADR) of the 703 products was 4.8 m3/min but the number of air purifiers over the value increased to 62.5%~66.3% since 2018. The odor removal ratio showed a median of 86.0% which was higher than the certification criteria but had large differences in efficacy in the five test compounds. Removal efficiencies of each compound in terms of the median and ratio to the average value showed acetate > formaldehyde > toluene > ammonia > acetaldehyde in descending order with large variances. The median noise level average value from five positions of air purifiers was 47.7 dB(A). However the medians of the top position and the front, where purified air was vented out, were relatively higher in 49.8 dB(A) and 48.2 dB(A), respectively. Noise level ratio to noise criteria had a median value of 96.4%, which showed that most of the noise levels were distributed near the criteria limit. The probability of the noise level at 100% of the criteria was calculated ton 0.232, which indicated excess noise levels.

The use of air cleaners has become popular to quickly remove contaminants present in indoor air such as fine dust and fungi. However, fungal information is rarely available in the filters equipped in the air cleaners. This study was conducted in winter to examine fungal concentration and species in the air cleaner filters of ten residential houses located in Incheon, Seoul, Hwaseong, and Gimpo cities. Fungi were detected in nine out of eleven filters from the ten houses. The level of fungi in the filters ranged from 0 CFU/cm2 to 2,370 CFU/cm2. There were differences in the fungal concentration among the eleven filters. Filters from three houses revealed levels over 1,000 CFU/cm2. The operation time of air cleaners did not seem directly related to the level of fungal concentration. A total of 326 isolates were obtained and classified as six genera belonging to Alternaria, Aspergillus, Cladosporium, Fusarium, Penicillium, and Trichoderma. Among these six genera, 20 species including one Alternaria, one Aspergillus, three Cladosporium spp., two Fusarium spp., eleven Penicillium spp., and two Trichoderma were identified. There were species that cause allergic reaction, pneumoniae, mycosis, and plant disease. Three species were known species of mycotoxin producers. Aspergillus niger, Cladosporium cladosporioides, and Penicillium brevicompactum were the most frequently detected fungi both in the air and in the air cleaner filters. This is the first report of fungal communities present in the air cleaner filters of residential houses in Korea.

Fungus has been regulated as an air contaminant in indoor environments in Korea. To remove the contaminant, air purifiers have been used in houses. However, not much information on the status of fungal contamination in the indoor air of houses is available. The present study was carried out to investigate fungal concentration and species in the indoor air of houses using air purifiers in winter. The results of indoor air sampling of ten houses located in the cities of Incheon, Seoul, Hwaseong, and Gimpo showed that the level of fungi ranged from 9 CFU/ m3 to 782 CFU/m3. Eight out of ten houses showed a level of less than 165 CFU/m3 indicating that the fungal level is generally low. Only one house exceeded the Korean regulatory standard value of 500 CFU/m3. A total of 175 isolates were obtained and classified as three genera belonging to Aspergillus, Cladosporium, and Penicillium. Among these three genera, 15 species including four Aspergillus spp., two Cladosporium spp., and nine Penicillium spp. were identified. Regarding the detection rate of the 15 identified fungal species, A. niger was the most detected species and followed by Cladosporium cladosporioides. Three to six species were present in the individual house that was investigated. Overall, our results showed that the level of fungal concentration and species diversity are low in the indoor air of houses that use air purifiers in winter.

Many air purifiers have been developed and released with increasing PM. In generally, the performance of air purifiers has been evaluated in the environment chamber by relevant standards. However, as there is a lack of information about air cleaning performance of air purifier in the living area, consumers have difficulty with product selection. In this study, five air purifiers were tested in apartments with different structures. In order to examine the effect of air purifiers, we assumed 3 cases such as inflow of pollutants from outdoors by ventilation, smoking patterns of residents, and cooking methods (e.g., frying fish). The evaluation results showed that the efficiency of air purifier products D and B of the 3-stage configuration (pre-filter + HEPA filter + activity carbon) was the best in most experiments. In the case of the ionizer type E product, the efficiency was very low and, at times, had increased the particulate matter indoors. Considering the cost-performance ratio, it is most reasonable to use an air purifier comprising a pre-filter and a HEPA filter without an additional configuration.

This study was performed to assess particulate matter removal efficiency of domestic air cleaner products in a field condition. The assessment also included air cleaners with different air removal mechanisms. The particulate matter (PM2.5) removal test with a different air removal mechanism using air cleaners showed that the electrostatic precipitation technique showed better performance compared with HEPA filters and other types of systems. Its removal efficiency was almost 95% in one of our operation times in the given test condition. It was assumed that not only the type of removal system but also the individual design, supply and exhaust system, and the automatically controlled air volume are involved in the removal efficiency. With respect to the area of application, tests with air cleaners for 40 m2, 60 m2, and 80 m2 areas revealed that particulate matter removal efficiency increased with the air cleaner that had a broad area of application. However, particulate matter removal efficiency by air cleaners did not correspondingly increase with the increase of the area of application. Moreover, the installation location did not influence particulate matter removal efficiency. Our results are expected to be used as the basic information for indoor air quality improvement and prediction using air cleaners.

This study was carried out considering that activated carbon physically adsorbs radon. Among the air cleaners equipped with activated carbon filter, eight air cleaners sold in Korea were selected and the radon reduction rate experiment was conducted. The instrument used an ionization chamber type instrument with a sensitivity of 3 CPM. The experiment was carried out by excluding the natural rate of reduction of radon in order to accurately grasp the radon reduction rate of activated carbon filter. Of the eight air purifiers, only three showed a reduction rate of more than 30%, while the remaining five air purifiers showed a reduction rate of less than 20%. This does not seem to be much different from the natural reduction rate. In addition, since it is not adsorbed by radon alone due to the nature of activated carbon, it is expected that the reduction rate will be lower in a real life environment.

In this study, a system was developed that can evaluate the radon gas removal efficiency of air cleaner filters. The system has three acrylic chambers connected in series;: the 1st chamber, the filter chamber and the 2nd chamber. In the 1st chamber, a radon source and an air pump were installed to create an environment with a constant radon concentration. Radon concentration in the two chambers was continuously monitored by ionization chamber detectors(RD-200, FRD1600, FTLab, Korea) and, in the 2nd chamber, the radon concentration increase of air filtrated by each filter was inter-compared. HEPA filters and two honeycomb type filters were evaluated. Results of HEPA filter, GAC 1 and GAC 2 were 1142 Bq, 7016 Bq and 12053 Bq, respectively. HEPA filter showed a significantly lower capacity for radon removal than the GAC filters. Also, the GAC 2 filter showed a more than 70 % better result compared to GAC 1 due to the difference in filter materials. Therefore, this system can be used to evaluate the radon removal ability of air cleaner filters, by filter type and filter material.

During periods where a fine dust watch was announced, we measured particulate matter by the light scattering method and the gravimetric method in accordance with the application of an air cleaner in 3 homes. The first investigation showed a lower indoor particulate matter 2.5 (PM2.5) concentration distribution than normal when there was a fine dust warning. Also, it was found that the result of the second research was similar to the first research, and was the effect of an air cleaner. The result of a comparison of black carbon (BC) concentration in accordance with an air cleaner at one room showed a lower concentration distribution than normal, as in the first and the second research when there was a fine dust warning. PM2.5 risk reduction effect showed 9.09E-5 (light scattering method) ~ 9.37E-5 (Gravimetric method) and 1.71E-4 (Light scattering method) ~ 1.76E-4 (Gravimetric method). Therefore, it was found that when there was a fine dust watch without ventilation, if air cleaner with the proper capacity is used and the influx of outside air reduced, the harmful effects of the fine dust can be lessened.

We estimated decreasing rate of indoor air pollutants with are airborne bacteria, airborne fungi, formaldehyde, total volatile organic compounds, PM10, and PM2.5 in 10 children’s hospitals and 6 childbirth houses located in Seoul and Gyeonggi-do from November to December in 2012. Sectional period was respectively divided for operating and non-operating the air cleaners. There was a trend that concentration of surveyed pollutants in children’s hospitals and childbirth houses during operating period decreased among indoor air. We used Monte-Calro simulation to remove uncertainty and identify efficiency of eliminated pollutants such as surveyed pollutants by the air cleaners. Average efficiency of removal were 61.39 ± 21.42% for airborne bacteria, 71.77 ± 19.65% for airborne fungi, 73.37 ± 24.62% for formaldehyde, 71.20 ± 25.96% for total volatile organic compounds, 65.16 ± 23.80% for PM10, and 71.06 ± 23.97% for PM2.5.

As indoor air cleaners have large sizes and high air flow rates, the test methods for particle cleaning capacity need to be reconsidered because the prescribed test chamber size becomes relatively smaller. In this study, air flow rate of air cleaners compared to test chamber size (Q/V) has been investigated by comparing the short-circuit factor which indicates the air mixed condition in the test chamber. The test method of Korea Air Cleaning Association (KACA) has been analysed and compared to that of Association of Home Appliance Manufacturers (AHAM) for clean air delivery rate (CADR) of two household air conditioners equipped with air cleaners having a maximum air flow rate of 15 m³/min in terms of initial particle concentrations, neutralized/non-charged particles, delay time before acquiring initial particle concentration, sampling positions. Constant short-circuit factor of about 0.9 was obtained in the range of Q/V less than 0.73 min^-1. CADR based on KACA test method was somewhat dependent on initial particle concentrations, delay time before acquiring initial concentration, sampling positions. However, CADR based on AHAM test method was less dependent. Two or three minutes of delay time before acquiring initial concentration was necessary to reduce the variation of CADR according to initial particle concentration and sampling position.

본 연구의 목적은 공기감염성 가축질병 유발의 주요 인자인 부유 세균 및 바이러스 등의 생물학상 인자들에 대한 유형별 공기청정기의 제균 효과를 비교 평가하는 데 있다. 시료 채취 장비에 대한 포집 성능 평가에서는 MS2 바이러스와 Pseudomonas fluorescens 모두 Button sampler보다는 Biosampler에 의한 채취 효율이 유의하게 높았다 (p<0.05). 공기청정기 유형 및 시료채취 방법에 관계없이 MS2 바이러스의 경우 초기 농도 대비 가동 후 5분에 50% 이상, 15분에 70% 이상, 30분에 80% 이상, 그리고 마지막 측정 시점인 60분에는 90% 이상의 제거 효율을 보이는 것으로 나타났다. P. fluorescens 세균의 경우 초기 농도 대비 가동 후 5분에 45% 이상, 15분에 50% 이상, 30분에 70% 이상, 그리고 마지막 측정 시점인 60분에는 75% 이상의 제거 효율을 보이는 것으로 나타났다. 유형별 공기청정기의 상대적 제균 효율을 비교해 보면 MS2 바이러스의 경우 이온 발생 방식>전기 집진 방식>습식 방식>건조 방식, P. fluorescens 세균의 경우 전기 집진 방식>이온 발생 방식>건조 방식>습식 방식의 순서로 조사되었다.

This paper presented experimental results for photocatalytic air cleaner removal performance for malodorous compounds generated from rest room. Photocatalytic oxidation (PCO) efficiency was up to 80∼ 90% for NH₃ in chamber, 29.3% for H2S, 79.6% for CH3SH, 58.8% for DMDS individually. PCO efficiency for DMS(Dimethy Sulfide) and DMDS(Dimethyl Disulfide) were relatively lower than that of NH₃ and CH3SH, this results indicate that DMS and DMDS removal process were effected by by-products of photocatalytic oxidation and humidity. Ozone was relatively low (below 5ppb) under the test conditions through photocatalytic oxidation. It is necessary to test a reliability of the air cleaner for a longtime under the various indoor conditions. But, prototype photocatalytic air cleaner will promise useful air cleaner for indoor air quality applications.

Test methods of Korea Air Cleaning Association (KACA) and Association of Home Appliance Manufacturers (AHAM) for particle cleaning capacity performance of an indoor air cleaner were compared in terms of the conditions of the test particle generation, the range of particle measurement and the calculation methods for particle cleaning capacity, and types of the test particles. The performance test was conducted in a 30 m³ chamber with the same test specimen and the test particles of each test were generated until the number concentration of 0.3 ㎛ particles reached 2.2 × 108 #/m³. The performance test results showed that the cleaning capacity with the particles of higher surface area and volume density, regardless of the type of test particles, was higher than with those of lower and the capacity from calculation with 0.3～1 ㎛ particles was higher than with 0.3 ㎛ particles. Moreover, the cleaning capacity with the calculation of KACA method was lower than with that of AHAM method in spite of using the same test specimen.

The fluidized bed has been used generally for Industrial process such as chemical reaction process, separation process, incineration and etc. It is very efficient for such application because of equitable contact of each fluidized element with fluid passing through it and maximizing active contact area to adsorb and react from the fluid. This study had focus on application of fluidized bed for air purifier as household appliance and analyzed its performance in comparison to typical fixed media type. As a result, fluidized bed performed in this study had higher removal efficiency for acetaldehyde over two times within initial operation term and had lower pressure drop over 0.7mmAq than that of fixed media type.