• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.1
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• pp.1-7
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• 2005

Although the Fourier Transform Infra-Red spectrophotometric Direct on Filter(FTIR-DOF) method is a useful analytical technique for quantifying quartz content in respirable dust samples, a number of analytical problems must be taken into consideration such as, to name only a few, inhomogeneous deposition of particles, level of environmental humidity, uneven surface of the filter, and interfering minerals in the sample. This study was designed to select the most suitable wavelength and proper filter material for the method, and to investigate effects of humidity and inhomogeneous deposition of particles on the filter. Samples of respirable dust, created in a dust chamber containing standard material of quartz, were collected using a cyclone equipped with a 25mm filter as a collection medium. The results were as follows; 1. Among seven (7) commercially available filters tested for the FTIR-DOF method, the DM 800 filter showed the best analytical performance having the lowest background absorbance bands and no overlapping peaks at 799, 779, and $695cm^{-1}$. 2. The variations of absorbance due to humidity ranged from 1.0% to 3.3% for $799cm^{-1}$, 1.0% to 3.3% for $779cm^{-1}$, and 8.9%~20.9% for $695cm^{-1}$ peaks, respectively. The $699cm^{-1}$ peak was proved to be most vulnerble to environmental humidity for quantitative analysis of quartz. 3. As for effects of inhomogeneous deposition of samples, the highest variation of absorbance of 10.9% ($13.5{\mu}g$) was observed when using the 695cm-1. The variations of absorbance from the other two peaks, 799 and $779cm^{-1}$, ranged from 1.2 to 3.2%, and 1.4 to 4.1%, respectively. Therefore, the $799cm^{-1}$ peak was considered to be most reliable for quantitative analysis of quartz. The results of this study suggest that, for quantitative analysis of quartz in the respirable dust samples, use of the $799cm^{-1}$ peak can minimize the influence of environmental humidity and inhomogeneous deposition of particles on the filter. The FTIR-DOF method, if adopted for routine analysis of quartz in the respirable dust samples, could save sample preparation time and efforts substantially and also could increase analytical throughputs. Since use of the $799cm^{-1}$ peak is prone to be affected by interferences in the sample, further research on minimizing the effects is needed.

• International Journal of Safety
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• v.1 no.1
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• pp.47-51
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• 2002

This study was performed by measuring the minimum ignition temperature of polyurethane form recovered from the recycling process of the end-of-life home appliances. The critical ignition temperature of polyurethane form was lower as the size of the sample vessel was increased, and that of polyurethane form using cyclopentane as the forming agent was relatively lower than the polyurethane form using CFC and the combustion of cyclopentane-polyurethane form occurred fiercely. It is considered that the recycling process of end-of-life home appliances using cyclopentane-polyurethane form as the insulator would require a special fire and dust explosion prevention measures since there exists a high potential hazard of fire and dust explosion during crushing and storage processes.

• Analytical Science and Technology
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• v.26 no.2
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• pp.113-119
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• 2013

The objective of this study was to understand the content characteristic of polybrominated biphenyl ethers in indoor household dust. Polybrominated diphenyl ethers (PBDEs) are widely used as additive brominated flame retardants (BFR) in electrical and electronic equipment, and insulation in the indoor environment, and may be released indoors via volatilization or as dusts. The indoor household dust samples were collected from January to December in 2011 and measured for the concentrations, congener profiles and possible sources of PBDEs. The concentrations of 22 congeners of PBDEs (the sum of PBDEs 47, 49, 66, 71, 77, 85, 99, 100, 119, 126, 138, 153, 154, 156, 183, 184, 191, 196, 197, 206, 207 and 209) were 35.22~575.88 ng/g for apartment dust samples and 524.44 ng/g for laboratory dust sample. The eight congeners of BDE-47, 153, 183, 196, 197, 206, 207, and 209 are detected in the more than 1 ng/g. The three congeners of BDE-206, 207 and 209 in all dust samples were detected.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.359-365
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• 2021

We investigated experimentally the ignition characteristic of dust and the hazard evaluating for electrostatic discharge. The ignition energy experiments were performed on sample dusts such as PE(HD), PE(LD), PMMA using the MIKE-3 apparatus. The formation of flame during the ignition of PE(HD) dust clouds occurred after the delay time of about 8 ms, and the flame kernels were not observed in center of ignition occurrence area. The voltage increased with increasing the number of dust dispersions and the increase rate of measured voltage with dust concentration was the highest in the order of PMMA, PE(LD) and PE(HD). For the effect of dispersion condition on the voltage in PE(HD) dust, the results were obtained that the voltage increased as the number of dispersions increased and as the concentration increased under the same dispersion number. The safety voltages to prevent fire and explosions by electrostatic ignition were estimated that PE(HD), PE(LD)-1, PE(LD)-2, and PMMA were 2.58, 44.72, 25.82, and 8.16 kV, respectively. We proposed the method for estimating the minimum ignition energy by using the measured voltage data for efficient investigation of electrostatic ignition hazard.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.589-609
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• 2017

This study carried out the density and energy dispersive X-ray spectroscopy and particle size analysis which are the physical characteristics of coal dust by collecting samples of coal dust in the five domestic mines to control the coal dust through ventilation in the workplace for coal mining in the country. This will contribute to a more comfortable working environment by understanding the physical characteristics of the coal dust which is derived from any hard coal produced domestically. In particular, the result of PSA analysis showed that the size of coal dust sample for this study ranged from $0.007{\sim}88.614{\mu}m$ were the particles less than $3.5{\mu}m$, the size range responsible for pneumoconiosis. To observe the flow of coal dust collected on the wind speed, the fallout of coal dust produced by the wind tunnel for the wind was measured and the particle size analysis of coal dust fallout was carried out. In addition, airborne dust is measured according to the mine velocity by using a multi-stage Anderson sampler in the mine where fine dust is generated in a large amount and the wind speed is found out to control the coal dust below $3.5{\mu}m$. In addition, natural ventilation pressure of A mine was calculated to prevent over design of the main fan.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.10 no.1
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• pp.104-114
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• 2000

This study was carried out to estimate current status of dust concentrations in the factories producing non-metallic products in Korea. Data were gathered from the environmental monitoring reports by 40 workplace environmental monitoring institutes and the questionnaire designed for the study by the authors. A total of 1838 dust samples from 368 plants were obtained from the reports and were analyzed with no data modifications. But data on asbestos, rock wool, and welding fumes were excluded in this evaluation. The factories were classified into eight groups according to the standard industrial classification scheme in Korea. The results of this study were as follows; 1. The factories included were glass, non-refractory ceramic, refractory ceramic ware, structural non-refractory clay and ceramic, cement and lime, articles of concretes, and stone. Mean(geometric mean) concentrations of total dust samples ranged from $1.75(0.84)mg/m^3$ to $5.87(2.84)mg/m^3$. Statistically significantly higher dust concentrations were found in the cement and lime industries compared with other industries. 2. The non-compliance rates were 15.2% in glass and 20.6% in other non-metallic mineral products industries. Although all institutions surveyed utilized the identical sampling and classification scheme for dusts as specified in the current occupational exposure limits, wide discrepancies were found in collecting samples and classifying dusts. Further problems were discovered in classifying dusts. A dust sample collected could be classified into any of the three groups regardless of silica content. The results of this study showed that dust concentrations in the non-metallic products industries varied widely. Also discovered was classification errors of dust types among workplace monitoring institutes. These errors could adversely affect the results of exposure assessments and the true nature of dust hazards. Further, no institutions performed respirable dust sampling and analysis of crystalline silica. In order to correct these malpractices, current standards of occupational exposure limits should be revised and tight supervision by the Ministry of Labour be suggested.

• Analytical Science and Technology
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• v.25 no.6
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• pp.476-482
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• 2012

Asian dust particles are known to have sizes ranging from a few nanometers up to about a few micrometers. The environmental and health effects depend on the size of the dust particles. The smaller, the farther they are transported, and the deeper they penetrate into the human respiratory system. Sedimentation field-flow fractionation (SdFFF) provides separation of nano to microparticles using a combination of centrifugal force and parabolic laminar flow in a channel. In this study, the steric mode of SdFFF (Sd/StFFF) was tested for size-based separation and characterization of Asian dust particles. Various SdFFF experimental parameters including flow rate, stop-flow time and field strength of the centrifugal field were optimized for the size analysis of Asian dust. The Sd/StFFF calibration curve showed a good linearity with $R^2$ value of 0.9983, and results showed an excellent capability of Sd/StFFF for a size-based separation of micron-sized particles.The optical microscopy (OM) was also used to study the size and the shape of the dust particles. The size distributions of the samples collected during a thick dust period were shifted towards larger sizes than those of the samples collected during thin dust periods. It was also observed that size distribution of the sample collected during dry period shifts further towards larger sizes than that of the samples collected during raining period, suggesting the sizes of the dust particle decrease during raining periods as the components adsorbed on the surface of the dust particles were removed by the rain water. Results show Sd/StFFFis a useful tool for size characterization of environmental particles such as the Asian dust.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.2
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• pp.196-208
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• 1997

This study was performed to estimate quartz contents in the both bulk and airborne dust samples and to determine particle size distribution of airborne dust from the selected foundry operations. Total dust samples were collected by a 37mm cassette and respirable by a 10 mm nylon cyclone. Particle size distributions were determined by a Marple's 8-stage cascade impactor at the melting, molding, shakeout and finishing operations. The presence of elements in the dust samples were confirmed by the scanning electron microscopy equipped with the energy dispersive x-ray spectrometry. The quartz contents were estimated using the intensity of the absorption peak of quartz at 799 cm-l by the Fourie Transformed Infrared Spectroscopy (FTIR). The results were as follows: 1. The analysis of data from cascade Impactor showed bimodal distributions of particle size at the melting, molding and shakeout operations. Mass median aerodynamic diameters for the distributions determined by histogram were $0.48-1.65{\mu}m$ for small and $13.43-19.58{\mu}m$ for large modes. In the dust samples collected at the finishing operations, however, only a large mode of $18.89{\mu}m$ was found. 2. The percentages of total to respirable dust concentration calculated from the impactor data ranged from 42 % to 66 %. The average concentrations of respirable dust by cyclone were $0.85-1.28mg/m^3$ collected from the workers, and were $0.23-0.56mg/m^3$ from the areas surveyed. Dust concentrations of personal samples were statistically significantly higher than those of area samples. The highest dust concentration was obtained from the personal samples of the finishing operation. 3. The mean percentages of silicon and oxygen estimated by SEM-EDXA in the bulk samples ranged from 35.83 % to 36.02 % and from 39.93 %-41.64 %, respectively. 4. The average quartz contents estimated by FTIR in the respirable dust from personal samples ranged from 4.32 % to 5.36 % and 4.54 % to 4.70 % in the bulk samples. No statistical difference of quartz content was found between foundry operations. In this study, quartz content was quantified by FTIR. Although no statistically significant difference in quartz content between airborne and bulk, samples and between different foundry operations was found, it is recommended that quartz content in the individual sample of respirable dust be analyzed and the results be used either to select an applicable quartz limits or to calculate the exposure limit. Further studies, however, are needed to compare the results by FTIR and XRD since it is reported that the quartz content determined by FTIR is different from that by XRD.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.59.2-59.2
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• 2013

The luminosity evolution of Type Ia supernova (SN Ia) and dust extinction play major roles in the systematic uncertainties in the SN cosmology. In order to overcome these obstacles, here we propose to use GMT-GMACS to take spectra for early-type host-galaxies of SNe Ia in the redshift range between 0.2 and 1.0. This high-redshift sample will be taken from Dark Energy Survey (DES), which expects more than 200 early-type hosts at this redshift range. They will be compared with nearby early-type hosts, for which we are now obtaining low-resolution spectra. We will select host-galaxies of same population age range for both nearby and high-redshift samples to reduce the possible evolution effect. Since we are dealing with early-type galaxies, our test is also less affected by dust extinction. We expect that our evolution-free and dust-free dark energy test will provide more robust results on the nature of dark energy.

• Resources Recycling
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• v.9 no.1
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• pp.21-26
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• 2000

Extraction of manganese was investigated with nitric acid from the dust which was generated in the AOD process producing a medium-low carbon ferromanganese from a high carbon ferromanganese. Content of manganese oxide in the dust was about 90%, and phase of it was confirmed as $Mn_3O_4$, The $Mn_3O_4$ particles was agglomerated as spherical shape, and had a lot of pore and crack inside. Maximum recovery of Mn from the sample in the leaching step was about 67% and residue was the amorphous $MnO_2$. The extraction of Mn increased with increasing temperature, but decreased in proportion to concentration of nitric acid. The extraction rate was in good agreement with the pore diffusion model.