안면부 여과식 방진마스크와 안경 동시 착용 시 불편감과 밀착계수 비교

어원석,최영보,신창섭,Eoh, Won Souk,Choi, Youngbo,Shin, Chang Sub 한국안전학회 2018 한국안전학회지 Vol.33 No.2

This study compares the differences of the fit factor by the order of wearing preference between Particulate filtering facepiece respirators(PFFR) and glasses when participants wore simultaneously and a survey of physical and visual complaint. Recognition level about fit of respirators was investigated and the educational (before- and after-) effect of the fit factor. When participants wore PFFR and glasses, physical complaints were nose pressure, slipping, nose and ear pressure, ear pressure and rim loosen, the most highly physical complaints were nose pressure. Visual complaints were demister, blurry vision, dizziness, visual field, and lens dirty, the most highly visual complaints were demister. But, there was significant difference in physical complaint such as nose pressure(10.3%), slipping (23.0%), nose and ear pressure(14.3%), and rim loosen(16.2%), visual complaint such as visual field(13.8%) and lens dirty(32.4%). For the recognition of fit of respirators, respirators fitness, leak site, an initial point and an object, faulty factor, recognition level was higher. Fit factor was increased after education of proper wearing of respirator. Change of the fit factor was smaller compared to the normal breathing and after 6 actions in case of after education. Questionnaire consisted of general characteristics and physical/visual complaint, recognition of fit. Complaints were measured after the QNFT with multiple choices. Quantitative fit factor was measured by device and compared the result of (before- and after-) educational effect. Also, we selected to 6 actions (Normal breathing, Deep breathing, Bending over, Turning head side to side, Moving head up and down, Normal breathing) among 8 actions OSHA QNFT (Quantitative Fit testing) protocol to measure the fit factors. The fit factor was higher after the training (p=0.000). Descriptive statistics, paired t-test, and Wilcoxon analysis were performed to describe the result of questionnaire and fit test. (P=0.05) Therefore, it is necessary to investigate the quantitative research such as training program and glasses fitting factor about the wearing of PFFR and glasses simultaneously.

강의실 CO₂ 발생률과 자연환기 특성의 측정 및 CFD 분석

이동해,최영보,Lee, Donghae,Choi, Youngbo 한국안전학회 2021 한국안전학회지 Vol.36 No.1

Lecture rooms are crowded with many attendees. Moreover, they rely significantly on the natural ventilation through windows for removing and controlling indoor contaminants such as CO₂. With the aim of broadening the understanding of the characteristics of natural ventilation phenomena in lecture rooms, the average individual CO₂ release rates of attendees were measured during the course of a lecture and compared with previously reported CO₂ release rates. In addition, the effects of natural ventilation through windows on the time-variant CO₂ concentrations in the center of the lecture room were measured and analyzed. Moreover, details about the overall and regional CO₂ concentrations, as well as the air flows in the lecture room, were simulated and analyzed with computational fluid dynamics software, Fluent 2020 R2. It was found that the average individual CO₂ release rates were slightly slower than previously reported rates. The local CO₂ concentrations in the lecture room for regions with a high density of attendees increased over a short period of time, although the natural ventilation was already started by opening the windows. The overall CO₂ concentration in the lecture room rapidly decreased in the early stage of ventilation, but declined very slowly after a longer period of ventilation time. Therefore, in order to enhance the efficiency of a lecture room's natural ventilation, it is recommended to homogeneously distribute the attendees in the lecture room, and to frequently open the windows for short periods of time.

안면부 여과식 방진 마스크의 형태 및 착용 방법 교육이 밀착계수에 미치는 영향 비교

어원석 ( Won Souk Eoh ),최영보 ( Youngbo Choi ),신창섭 ( Changsub Shin ) 한국안전학회(구 한국산업안전학회) 2016 한국안전학회지 Vol.31 No.5

Particulate filtering facepiece respirators (PFFR) is one of the most widely used items of personal protective equipments, and a tight fit of the respirators on the wearers is critical for the protection effectiveness. In order to effectively protect the workers through the respirators, it is important to find and evaluate the ways that can be readily applicable at the workplace to improve the fit of the respirators. This study was designed to evaluate effects of mask style (cup or foldable type) and donning training on fit factors (FF) of the respirators, since these are available at various workplace, especially at small business workplace. A total of 40 study subjects, comprised of 30~50s aged male and female workers in metalworking industries, were enrolled in this study. The FF were quantitatively measured before and after training related to the proper donning and use of cup or foldable-type respirators. The pass/fail criterion of FF was set at 100. After the donning training for the cup-type mask, subjects who passed the fit test were increased from 10 to 33. Moreover, the geometric mean (GM) of FF was increased by 340% in subjects who failed the test. In addition, the training effects for the cup-type mask were significant in female and 50s aged subjects. On the other hand, although the GM of FF for the foldable-type mask was also increased after the donning training, the GM of FF for the foldable-type mask and it’s increase rate were smaller as compared to the cup-type mask. Furthermore, the differences of the increase rates of the GM of FF in sex and aged of the subjects were not significantly for the foldable-type mask. The multi-distribution of leak points for the foldable-type mask may be one of causes for the less effect of training on the fit of the foldable-type mask. These results imply that the raining on the donning and use of PFFR can enhance the protection effectiveness of cup or foldable-type mask, and that the training effects for the foldable-type mask is less significant than that for the cup-type mask. Therefore, It is recommended that the donning training and fit tests should be conducted before the use of the PFFR, and that efficient tranining programs for the foldable-type mask are required.

건물의 유효누출면적 및 박스모델을 이용한 염소 실내 누출의 위험지역 완화에 관한 연구

곽솔림 ( Sollim Kwak ),이은별 ( Eunbyul Lee ),최영보 ( Youngbo Choi ) 한국안전학회(구 한국산업안전학회) 2018 한국안전학회지 Vol.33 No.5

It is difficult to determine the outdoor toxic level of hazardous chemicals that are leaked in the building, since there are no efficient ways to calculate how much percentage of the leaked chemicals is released into the outdoor atmosphere. In address to these problems, we propose a reasonable box model that can quantitatively evaluate the mass rate of the indoor chlorine leakage into the outside of the building. The proposed method assumes that the indoor chlorine leakage is fully mixed with the indoor air, and then the mixture of the chlorine and indoor air is exfiltrated into the outside of the building through effective leakage areas of the building. It is found that the exfiltration rate of the mixture of the chlorine and indoor air is strongly dependent on the temperature difference between inside and outside the building than the atmospheric wind speed. As compared with a conventional method that uses a vague mitigation factor, our method is more effective to evaluate the outdoor toxic threat zone of the chlorine that are leaked in the building, because it can consider the degree of airtight of the building in the evaluation of the threat zone.

화학물질 저장 탱크와 방류벽 사이의 공간 부족 개선을 위한 누출 방지판의 안정성 평가 기준

이은별 ( Eunbyul Lee ),곽솔림 ( Sollim Kwak ),최영보 ( Youngbo Choi ) 한국안전학회(구 한국산업안전학회) 2018 한국안전학회지 Vol.33 No.5

The Chemical Controls Act strictly regulates for the chemical companies to establish sufficient space between the liquid chemical tank and dike, but facilities already installed suffer from the space shortage between the tank and dike. Installing leakage preventing plates on the dike is considered as one of the economic solutions that can alleviate the space deficiency. However, there is no technical and reasonable criterion for the safety evaluation of the leakage preventing plate on the dike. In order to address this problem, we provide generalized and verified calculating equations that give maximum height and horizontal distance of leakage trajectories. Through the proposed equations, proper heights of the leakage preventing plates on the dike can be easily determined. In this study, new calculating methods are also developed to determine the impact force of the liquid to the leakage preventing plates. In addition, we performed the reactivity experiments between four corrosive liquid chemicals and two stainless steel materials that are candidate substances for the construction of the leakage preventing plate. The results of this study is expected to be applicable as a guideline in the design of safe dike and its leakage preventing plates.

Keggin형 헤테로폴리산에 의한 과당의 5-하이드록시메틸퍼퓨랄로의 전환을 위한 탈수반응

백자연(Jayeon Baek),윤형진(Hyeong Jin Yun),김남동(Nam Dong Kim),최영보(Youngbo Choi),이종협(Jongheop Yi) 한국청정기술학회 2010 청정기술 Vol.16 No.3

과당(fructose)로부터 간단한 공정을 통하여 바이오디젤보다 우수한 청정에너지 연료로 알려진 5-하이드록시메틸퍼퓨랄(HMF)을 제조하는 청정공정을 개발하였다. 이 연구에서는 중심원소와 배위원소가 치환된 네 종류의 헤테로폴리산 HnXM12O40 (중심원소 X = P, Si, 배위원소 M = W, Mo.)을 과당으로부터 HMF로 전환하는 탈수반응에 적용하고, 그 반응활성을 비교하였다. 헤테로폴리산의 산 세기는 중심원소가 P, 배위원소가 W일 때 더 높았으며 산 점의 수는 이와 반대되는 경향을 보였다. 과당의 HMF로의 탈수반응은 헤테로폴리산의 산 특성과 음이온의 연성(softness)과 밀접한 관련이 있으며, 촉매 활성점과 전환율이 상쇄작용하여 네 종류의 헤테로폴리산 촉매는 서로 비슷한 활성을 보였다. 또한 반응에 사용된 헤테로폴리산을 반응온도보다 높은 200℃에서 열처리한 후에도 그 결정구조가 유지되는 것을 확인하였으며, 이를 통하여 헤테로폴리산의 반응활성이 안정적으로 유지됨을 확인할 수 있었다. Four Keggin-type heteropolyacids, HnXM12O40(X = P and Si, M = W and Mo) that were substituted with heteroatom and polyatom were applied to the dehydration reaction of fructose to 5-hydroxymethylfurfural (HMF). The results showed that the acid became stronger when the heteroatom and polyatom were substituted with P and W than the cases of Si and Mo, respectively. However, the amount of acidic sites increased with the decrease in the acid strength, resulting in the change of the catalytic activity of heteropolyacids in the dehydration reaction. The experimental results revealed that four different heteropolyacids produced similar amounts of HMF via the dehydration reaction of fructose due to the counterbalancing effect between the amount of active sites, which is related to the catalytic activityof heteropolyacids, and the softness of polyanion. In addition, it was observed that the prepared heteropolyacids showed good structural stability after heat treatment at 200℃.