• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.1-8
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• 2006

The purpose of this study was to evaluate the efficiency of a passive sampler in measuring atmospheric ammonia concentrations using chamber system. The ability of the passive sampler to quantitatively determine atmospheric ammonia gas was almost identical to that of the reference method (indophenol method). There was no significant difference between concentrations measured by the two methods. The detection and quantification limits of the ammonia passive sampler were 16.9 ppb and 25.3 ppb, respectively, for a 24-h sampling period. The average coefficient of variation between replicated samplers was $6.7{\pm}4.2%$. The concentrations measured by the two methods (passive sampler and indophenol method) were no significant difference with good a correlation (correlation coefficient=0.964).

• Analytical Science and Technology
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• v.34 no.1
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• pp.23-35
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• 2021

In order to measure the volatile organic compounds (VOCs) of a sample which is too large to use commercially available chamber, a stainless steel vacuum chamber (VC) (with an internal diameter of 205 mm and a height of 50 mm) was manufactured and the temperature of the chamber was controlled using an oven. After concentrating the volatiles of the sample in the chamber by helium gas, it was made possible to remove residual volatile substances present in the chamber under reduced pressure ((2 ± 1) × 10-2 mmHg). The chamber was connected to a purge & trap (P&T) using a 6 port valve to concentrate the VOCs, which were analyzed by gas chromatography-mass spectrometry (GC-MS) after thermal desorption (VC-P&T-GC-MS). Using toluene, the toluene recovery rate of this device was 85 ± 2 %, reproducibility was 5 ± 2 %, and the detection limit was 0.01 ng L-1. The method of removing VOCs remaining in the chamber with helium and the method of removing those with reduced pressure was compared using Korean drinking water regulation (KDWR) VOC Mix A (5 μL of 100 ㎍ mL-1) and butylated hydroxytoluene (BHT, 2 μL of 500 ㎍ mL-1). In case of using helium, which requires a large amount of gas and time, reduced pressure ((2 ± 1) × 10-2 mmHg) only during the GC-MS running time, could remove VOCs and BHT to less than 0.1 % of the original injection concentration. As a result of analyzing volatile substances using VC-P&T-GC-MS of six types of cell phone case, BHT was detected in four types and quantitatively analyzed. Maintaining the chamber at reduced pressure during the GC-MS analysis time eliminated memory effect and did not affect the next sample analysis. The volatile substances in a cell phone case were also analyzed by dynamic headspace (HT3) and GC-MS, and the results of the analysis were compared with those of VC-P&T-GC-MS. Considering the chamber volume and sample weight, the VC-P&T configuration was able to collect volatile substances more efficiently than the HT3. The VC-P&T-GC-MS system is believed to be useful for VOCs measurement of inhomogeneous large sample or devices used inside clean rooms.

• Asian Journal of Atmospheric Environment
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• v.8 no.4
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• pp.175-183
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• 2014

To visually and chemically verify the rainout of soot particles, a model experiment was carried out with the cylindrical chamber (0.2 m (D) and 4 m (H)) installing a cloud drop generator, a hydrotherometer, a particle counter, a drop collector, a diffusing drier, and an artificial soot particle distributer. The processes of the model experiment were as follows; generating artificial cloud droplets (major drop size : $12-14{\mu}m$) until supersaturation reach at 0.52%-nebulizing of soot particles (JIS Z 8901) with an average size of $0.5{\mu}m$-counting cloud condensation nuclei (CCN) particles and droplets by OPC and the fixation method (Ma et al., 2011; Carter and Hasegawa, 1975), respectively - collecting of individual cloud drops - observation of individual cloud drops by SEM - chemical identifying of residual particle in each individual droplet by SEM-EDX. After 10 minutes of the completion of soot particle inject, the number concentrations of PM of all sizes (> $0.3{\mu}m$) dramatically decreased. The time required to return to the initial conditions, i.e., the time needed to CCN activation for the fed soot particles was about 40 minutes for the PM sized from $0.3-2.0{\mu}m$. The EDX spectra of residual particles left at the center of individual droplet after evaporation suggest that the soot particles seeded into our experimental chamber obviously acted as CCN. The coexistence of soot and mineral particle in single droplet was probably due to the coalescence of droplets (i.e., two droplets embodying different particles (in here, soot and background mineral particles) were coalesced) or the particle capture by a droplet in our CCN chamber.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.114-122
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• 2024

NF₃, Chamber cleaning gas, has a high Global Warming Potential (GWP) of 17,000, causing significant greenhouse effects. Reducing gas usage during the cleaning process is crucial while increasing the cleaning Rate and reducing cleaning standard deviation (Stdev). In a previous study with a 6-inch PECVD chamber, a multiple linear regression analysis showed that Power and Pressure had no significant effect on the cleaning Rate because of their P-values of 0.42 and 0.68. The weight for Flow is 11.55, and the weights for Power and Pressure are 1.4 and 0.7. Due to the limitations of the research equipment, which differed from those used in actual industrial settings, it was challenging to assess the effects in actual industrial environment. Therefore, to show an actual industrial environment, we conducted the cleaning process on a 12-inch PECVD chamber, which is production-level equipment, and quantitatively analyzed the effects of each variable. Power, Pressure, and NF3 Flow all had P-values close to 0, indicating strong statistical significance. The weight for Flow is 15.68, and the weights for Power and Pressure are 4.45 and 5.24, respectively, showing effects 3 and 7 times greater than those with the 6-inch equipment on the cleaning rate. Additionally, we analyzed the cleaning Stdev and derived that there is a trade-off between increasing the cleaning Rate and reducing the cleaning Stdev.

• Journal of Environmental Health Sciences
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• v.46 no.5
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• pp.555-564
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• 2020

Objectives: To identify and investigate through qualitative and quantitative analysis the hazardous substances generated when compressed wood was burned at a live fire-training center. Methods: Four types of compressed wood that are actually used in live fire training were burned in a chamber according to KS F2271. The gaseous material was sampled with a gas detector tube and conventional personal samplers. Results: 1,3-butadiene, benzene, toluene, xylene, formaldehyde, hydrogen chloride, hydrogen cyanide, ammonia, carbon monoxide, and nitric acid were detected. In particular, 1,3-butadiene (497.04-680.44 ppm), benzene (97.79-125.02 ppm), formaldehyde (1.72-13.03 ppm), hydrogen chloride (4.71-15.66 ppm), hydrogen cyanide (3.64-8.57 ppm), and sulfuric acid (3.85-5.01 ppm) exceeded the Korean Occupational Exposure Limit as measured by sampling pump according to the type of compressed wood. Conclusions: We found through the chamber testing that firefighters could be exposed to toxic substances during live fire training. Therefore, firefighter protection is needed and more research is required in the field.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.183-190
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• 2011

This study investigated the emissions characteristics of air freshener using small emission chamber method. The emission of VOCs from air freshener were determined in the small chambers in the temperature (25, $30({\pm}1)^{\circ}C$), relative humidity ($50{\pm}5%$), ventilation rate (0.3, 0.5, ($0.8({\pm}0.005)/hr$), and sample loading factor ($1.4{\sim}551.0g/m^2$) in this study. The emission tests from air freshener for sample loading factor resulted in TVOC emission rates of $0.7{\sim}64.4mg/m^2{\cdot}h$ after 5 hours. For most target VOCs such as limonene, ${\alpha}$-pinene and linalool, higher temperature and ventilation rate levels exhibited increased emission rates.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.23 no.2
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• pp.97-108
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• 1994

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.677-683
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• 2016

In urban areas, underground tunnel construction sites have spread widely to accommodate rapidly increasing traffic volume along with a high-degree economic growth. Earth tunneling might be adapted frequently for the underground space securing, and various tunneling methods have been developed to stabilize the tunnel face and crown. Among them, the DSM (divided shield method) is gaining popularity for its enhanced stability and construction efficiency. This method has its foundation from the Messer Shield method, which is one of the trenchless special tunneling methods. This study examined the effects of face reinforcement on construction the sequence through a large scale soil chamber test and numerical analyses. The chamber has a size of a 1/2 scale of the real tunnel. Surface settlements were measured according the tunneling process. Commercially available software, MIDAS GTS, was used for numerical analysis and its result was compared with the values obtained from the chamber test. The results of the study show that both settlements of the embanked soils and the stress of the tunnel girder are located within the safe criteria. Overall, this study provides basic data and the potential of using a reinforced tunnel face to enhance DSM applications.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.6
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• pp.789-800
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• 2013

$N_2O$ and $CH_4$, Greenhouse gas emission, Forest soil, Closed chamber technique, Soil uptake $N_2O$ and $CH_4$ are important greenhouse gases (GHG) along with $CO_2$ influencing greatly on climate change. Their soil emission rates are highly affected by bio-geo-chemical processes in C and N through the land-atmosphere interface. The forest ecosystems are generally considered to be net emission for $N_2O$; however, net sinks for $CH_4$ by soil uptake. Soil $N_2O$ and $CH_4$ emissions were measured at Mt. Taewha in Gwangju, Kyeonggi, Korea. Closed chamber technique was used for surface gas emissions from forest soil during period from May to October 2012. Gas emission measurement was conducted mostly on daytime (from 09:00 to 18:00 LST) during field experiment period (total 25 days). The gas samples collected from chamber for $N_2O$ and $CH_4$ were analyzed by gas chromatography. Soil parameters were also measured at the sampling plot. GHG averages emissions during the experimental period were $3.11{\pm}16.26{\mu}g m^{-2}hr^{-1}$ for $N_2O$, $-1.36{\pm}11.3{\mu}gm^{-2}hr^{-1}$ for $CH_4$, respectively. The results indicated that forest soil acted as a source of $N_2O$, while it acted like a sink of $CH_4$ on average. On monthly base, means of $N_2O$ and $CH_4$ flux during May (spring) were $8.38{\pm}48.7{\mu}gm^{-2}hr^{-1}$, and $-3.21{\pm}31.39{\mu}gm^{-2}hr^{-1}$, respectively. During August (summer) both GHG emissions were found to be positive (averages of $2.45{\pm}20.11{\mu}gm^{-2}hr^{-1}$ for $N_2O$ and $1.36{\pm}9.09{\mu}gm^{-2}hr^{-1}$ for $CH_4$); which they were generally released from soil. During September (fall) $N_2O$ and $CH_4$ soil uptakes were observed and their means were $-1.35{\pm}12.78{\mu}gm^{-2}hr^{-1}$ and $-2.56{\pm}11.73{\mu}gm^{-2}hr^{-1}$, respectively. $N_2O$ emission was relatively higher in spring rather than other seasons. This could be due to dry soil condition during spring experimental period. It seems that soil moisture and temperature mostly influence gas production and consumption, and then emission rate in subsoil environment. Other soil parameters like soil pH and chemical composition were also discussed with respect to GHG emissions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2343-2350
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• 2013

The wave height distributions in front of a vertically perforated wall structures for obliquely incident uni-directional irregular waves are mainly investigated by using 3D hydraulic experiments. The difference and similarity of wave propagation along the plain and perforated wall structures are investigated and particularly the effects of side walls in chamber and relative chamber width are analyzed. This study shows that the wave height distribution patterns for normalized wave heights in front of structure is significantly different between the plain and perforated wall structures, and the side wall in the chamber suppresses the growth of waves.