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This survey was designed to investigate the concentrations of respirable coal dust samlples by work processes and other environmental factros in the coal mining industry. Respirable coal dust samples were collected from 5 coal mines utilizing NIOSH methods 7602 during the period from July 7th to July 29th, 1992. Silica contents were determined by Fourier Transform Infrared Spectrophotometry. The results were as follows: 1. The geometric means (standard deviation) were 3.97(2.87)mg/m³in picking work,7.28 (4.35)mg/m³in caving work of coal face, 0.60(2.20)mg/m³in drilling work, 0.63(3.49)mg/m³in carring work, 1.78(5.88)mg/m³in coal chuting and 3.27(3.72)mg/m³in separating work. Although being measured at the same coal face, the concentrations of respirable dust significantly higher in caving work than in coal picking work. 2. The geometric means of silica contents in respirable dust were significantly higher in drilling work (7.32%) than in coal face (1.98%) and in separating work (3.04%). This results implies that drilling workers would be more susceptible to contracting silicosis than other workers. 3. The means of CO and CO?? concentration after explosion were 98 ppm and 8,159ppm in coal face, and 200ppm, and 11,200ppm in drilling work. However, those before explosion were 1.8ppm and 2,175ppm in coal face, and 2,118ppm in drilling work. 4. The levels measured near auger drill, drilling machine and separating work at coal face were 106dB(A),110dB(A) and 111dB(A), respectively. 5. Mean air velocities at coal face, drilling and transportation way markedly lower than those of OSHA recommended standard (0.15m/sec), accounting for 0.07m/sec,0.09m/sec and 0.1m/sec, respectively.
Objectives: 21 sepiolite substances produced in China were investigated for the presence of asbestos in their materials. Materials and methods: In order to identify asbestos in sepiolite substances, test materials were analyzed using a transmission electron microscope equipped with energy dispersive X-ray spectrometer(TEM-EDS) for confirming their shape and components(atomic %). Results: Five of 21 sepiolte substances were asbestos-containing materials. Two chrysotile containing sepiolite proved to be asbestoscontaining materials, as did two chrysotile mixed with tremolite containing sepiolite. 16 sepiolite substances did not contain asbestos materials. Conclusions: When importing sepiolite substances, they must be analyzed to determine if there is asbestos in their materials.
Open surface tanks are used in a variety of industrial processes, such as picking and plating. Push-pull ventilation system is often the best and most energy efficient way to remove any contaminant which evaporates from the open surface tanks. Existing design guidelines are based on experimental and numerical works which is cannot easily be extended to different operating conditions. Contaminant removal efficiency of push-pull ventilation could be affected by various parameters, such as vessel shape, room location, cross draft, etc. Especially, the velocity of cross draft might be one of influencing factors for the effective ventilation. To account for the effect of cross draft in case of over 0.4m/s, a flow adjustment of ±20% should be designed into the push and +20% into the pull flow system. For effective design and installation of push-pull system, we must be consider the magnitude of Cross draft velocity. However, the cross draft velocity of workplace installed push-pull ventilation system were not measured yet. In this paper, we measured the cross draft and door/window face velocities in 8 surface treatment shops in which the push-pull type open surface tanks are generally used. Two-directional hot-wire anemometer was used to measure the velocities after checking the main direction of flow by using smoke-tube. The experiments were performed in both winter and summer since the flow patterns and the velocities were thought to show the quite different seasonal variations. Mean cross draft velocities of winter and summer were measured as 0.60m/s and 0.62m/s, respectively, which is over the operating range, 0.4m/s. In addition, the face velocities through doors and windows were measured as 1.38m/s and 1.79m/s, respectively. The measured cross draft velocity is somewhat higher than 0.4m/s which is recommended for the push-pull hood by ACGIH design guideline. This high cross draft velocity could destroy the hood flow in the push-pull hood system. Thus, it is imperative that the ACGIH design guide line should be modified in the near future.
A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank in recent years. Efficiency of push pull hood system is affected by various parameters, such as cross draft, vessel shapes, size of tanks surface, liquid temperature, and so on. Among these, velocity of cross draft might be one of the most influencing factor for determining the ventilation efficiency. To take account of the effect of cross draft velocities over 0.38m/s, a flow adjustment of ±20% should be considered into the push and +20% into the pull flow system. Although there are many studies about the efficiency evaluation of push pull hood system based on CFDs (Computational Fluid Dynamics) and experiments, there have been no reports regarding the influence of velocities and direction of cross-draft on push-pull hood efficiency. This study was conducted to investigate the influence of cross draft direction and velocities on the capture efficiency of the push-pull ventilation system. Smoke visualization method was used along with mock-up of push-pull hood systems to verify the ventilation efficiency by experiments. When the cross-draft blew from the same origins of the push flows, the efficiency of the system was in it`s high value, but it was decreased significantly when the cross-draft came from the opposite side of push flows. Moreover, the efficiency of the system dramatically decreased when the cross-draft of open surface tank was faster than 0.4m/s.
The purpose of this study is to validate and verify a head nose exposure inhalation system for nano particle inhalation toxicity studies. Carbon nano tube(CNT) particles were generated by a chemical vapor deposition(CVD) generator. And purchased single wall carbon nanotubes(SWCNT) and multi wall carbon nanotubes(MWCNT) were generated by an atomizer. CNT particle distribution was measured by Scanning Nano-Particle Spectrometer(SNPS) and Condensation Particle Counter(CPC). Diameter and length of MWCNT generated by CVD were 10~40 nm and 220~20 μm respectively. Particle number concentration of MWCNT generated by CVD were 1.3×105, 4.1×104, 5.6×103#/cc in high, middle, low chamber respectively. Distribution of particles which were less than 100 nm was 45%. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 8.5×106, 5.3×105, 1.1×104#/cc and after sonication 6.7×106, 4.1×105, 9.5×103#/cc in high, middle, low chambers respectively. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 6.7×106, 4.6×105, 8.6×103#/cc and after sonication 7.7×106, 5.1×105, 1.3×104#/cc in high, middle, low chambers respectively. We set up head nose exposure inhalation system to conduct a study on nano particle inhalation toxicity. There were sufficient particle number concentrations of nano particles generated in each chamber.
The purpose of this study is to investigate information on performance of ventilation in high-tech microelectronicscleanrooms using computational fluid dynamics (CFD). One liquid crystal display (LCD) company was examinedfor evaluating the relationship between workplace concentration and ventilation rate efficiency by using CFDsoftware, Airpak 3.0v. Acetone concentration in cleanroom for final packing process, which is inspected LCD was40.1ppm (GSD 1.91) (n=55) as geometric mean, ranged 7.8~128.7ppm and weakly correlated with ventilationrate efficiency (R²=0.37, p<0.01). Resulting from computational fluid dynamics (CFD), acetone concentrationcan be reduced 62% when install booth type local exhaust system, the most efficient way among 10 other differentventilation methods like increasing volume of general ventilation, changing the location of workers, supply orexhaust diffusers and install downstream type local exhaust system, etc. We found that volitile organic compoundsin cleanroom can be a matter of adverse health effects and the concentration was correlated with ventilation rateefficiency. The most optimized plan to control the contaminants in solvent cleaning work in cleanroom was boothtype local exhaust system.
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The purpose of this study is to validate and verify a head nose exposure inhalation system for nano particle inhalation toxicity studies. Carbon nano tube(CNT) particles were generated by a chemical vapor deposition(CVD) generator. And purchased single wall carbon nanotubes(SWCNT) and multi wall carbon nanotubes(MWCNT) were generated by an atomizer. CNT particle distribution was measured by Scanning Nano-Particle Spectrometer(SNPS) and Condensation Particle Counter(CPC). Diameter and length of MWCNT generated by CVD were 10~40 nm and 220~20 µm respectively. Particle number concentration of MWCNT generated by CVD were 1.3×105 , 4.1×104,5.6×103#/cc in high, middle, low chamber respectively. Distribution of particles which were less than 100 nm was 45%. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 8.5×106,5.3×105 , 1.1×104#/cc and after sonication 6.7×106, 4.1×105 , 9.5×103#/cc in high, middle, low chambers respectively. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 6.7×106, 4.6×105, 8.6×103#/cc and after sonication 7.7×106, 5.1×105 , 1.3×104#/cc in high, middle, low chambers respectively. We set up head nose exposure inhalation system to conduct a study on nano particle inhalation toxicity. There were sufficient particle number concentrations of nano particles generated in each chamber.
The use of nanoparticles (NPs) in industry is increasing, bringing with it a number of adverse health effects on workers. Like other chemical carcinogens, NPs can cause cancer via oxidative DNA damage. Of all the molecules vulnerable to oxidative modification by NPs, DNA has received the greatest attention, and biomarkers of exposure and effect are nearing validation. This review concentrates on studies published between 2000 and 2012 that attempted to detect oxidative DNA damage in humans, laboratory animals, and cell lines. It is important to review these studies to improve the current understanding of the oxidative DNA damage caused by NP exposure in the workplace. In addition to examining studies on oxidative damage, this review briefly describes NPs, giving some examples of their adverse effects, and reviews occupational exposure assessments and approaches to minimizing exposure (e.g., personal protective equipment and engineering controls such as fume hoods). Current recommendations to minimize exposure are largely based on common sense, analogy to ultrafine material toxicity, and general health and safety recommendations.