A Study on The Development of Local Exhaust Ventilation System (LEV’s) for Installation of Laser Cutting Machine

The Local Exhaust Ventilation (LEV) is the most common type of engineering control equipment used to control employees' exposure to chemicals that are hazardous to their health. Before a contaminant disperses into the workroom environment, LEV systems operate on the principle of capturing it at or near its source. The welding guideline stated that the suggested minimum hood velocity is 100 ft/min, the recommended velocity along ducts for vapors, gases, and smoke is 1000 ft/min, and 2000 ft/min. The research objective is to identify the effectiveness of the LEV system using validation computational fluid dynamics (CFD) simulation. The data collected by experimental design during the pre-testing phase of the LEV system is quantitative and obtained through a fieldwork survey and document analysis. Findings found that LEV systems are effective to be used and meet all the minimum requirements set by the guideline. In CFD simulation, upon validation, the average absolute error obtained from the case study is 8.4%. There is good agreement between actual experimental and CFD simulation results, and the acceptable validity of CFD simulation is less than 10%. Therefore, simple CFD modeling is a tool to simulate air velocity in the LEV system, saving labor costs and time consumption during the earliest stage of LEV design development before actual construction. This study's outcome can serve as a benchmark or guideline for training facilities equipped with the LEV system to prioritize safety and health.

To control chemical hazard, engineering control is one of the Hierarchy of Controls that protects workers from chemical hazard. Engineering control is accomplished by removing hazardous conditions by placing a barrier between the worker and the hazard. Local ventilation system is widely used in laboratories to remove any chemical agents that are released from any chemical reactions. The importance of these ventilation systems is to prevent any health complications to persons in the laboratory due to chemical exposure. İn this paper, the effects and effectiveness of sash height to vapor source position to effectiveness of local exhaust ventilation (LEV) system were studied and identified using vapor flow from the stimulated carbon dioxide (CO2) and water vapor. Eight LEVs were inspected. The stimulated vapor as a tracer was produced by mixing dry ice into hot-boiled water (100oC). The dispersion stimulated CO2 and water vapor inside and outside the LEV system, and this can predict the efficiency of LEV systems based on visual inspection. The results revealed that each LEV showed a different time taken to draw out the vapor from the inside of the fume hood.

The performance of a commercially available Local Exhaust Ventilation (LEV) system for controlling mist, vapor and fume exposures during two-piece slim retractable aluminium can production line was assessed. This study focused on monitoring of LEV system performance in different phases of production which are drawing and wall ironing. Data such as static pressure, velocity pressure, transport velocity and flow rate values was obtained as a specific requirement to analyze the performance of the system. The first LEV system used to control mist exposure from drawing activities and the second system was implemented to control fume and vapor during ironing wall process. The performance of the system was investigated and compared with standard as required by USECHH Regulation 2000. The results of LEV system monitoring were discussed and several recommendations were proposed to improve the performance of the system and to reduce the mist, fume and vapor exposure for occupational safety and health purposes.

Acute and chronic exposure to xylene can result in a range of negative health effects. However, xylene is widely used and emitted in the air of workplaces. To evaluate xylene vapor concentrations to guide the design and evaluation of a local exhaust ventilation (LEV) system to reduce exposure in a pesticide production factory. A real time volatile organic compound (VOC) monitor was used to determine the workers' time-weighted average (TWA) exposure. A LEV system was designed, and then, workers' exposure to xylene vapor was evaluated. We found that worker's exposure to xylene (4·7±5·5 ppm) was lower than the standards recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) and the Occupational safety and health administration (OSHA). Despite the low TWA exposures, the short-term exposures for some workers were higher than STEL levels. Three canopy hoods were designed and installed with capture velocities of 0·508 m second(-1) and duct velocity of 10·16 m second(-1). We found that an exhaust ventilation system had a significantly reduced occupational exposure to xylene vapor.

Respirable crystalline silica dust exposure in residential roofers is a recognized hazard resulting from cutting concrete roofing tiles. Roofers cutting tiles using masonry saws can be exposed to high concentrations of respirable dust. Silica exposures remain a serious threat for nearly two million U.S. construction workers. Although it is well established that respiratory diseases associated with exposure to silica dust are preventable, they continue to occur and cause disability or death. The effectiveness of both a commercially available local exhaust ventilation (LEV) system and a water suppression system in reducing silica dust was evaluated separately. The LEV system exhausted 0.24, 0.13, or 0.12 m 3 /sec of dust laden air, while the water suppression system supplied 0.13, 0.06, 0.03, or 0.02 L/sec of water to the saw blade. Using a randomized block design, implemented under laboratory conditions, the aforementioned conditions were evaluated independently on two types of concrete roofing tiles (s-shape and flat) using the same saw and blade. Each engineering control (LEV or water suppression) was replicated eight times, or four times for each type of tile. Analysis of variance was performed by comparing the mean airborne respirable dust concentrations generated during each run and engineering control treatment. The use of water controls and ventilation controls compared with the “no control” treatment resulted in a statistically significant (p < 0.05) reduction of mean respirable dust concentrations generated per tile cut. The percent reduction for respirable dust concentrations was 99% for the water control and 91% for the LEV. Results suggest that water is an effective method for reducing crystalline silica exposures. However, water damage potential, surface discolorations, cleanup, slip hazards, and other requirements may make the use of water problematic in many situations. Concerns with implementing an LEV system to control silica dust exposures include sufficient capture velocity, additional weight of the saw with the LEV system, electricity connections, and cost of air handling unit.

Local exhaust ventilation systems for the gross anatomy laboratory

Introduction: One of the ways to control hazards with an engineering approach in an effort to reduce hazards due to chemical reactions in the laboratory is to install a ventilation system, especially in the Atomic Absorption Spectrophotometer (AAS). The research objectives of this study are to evaluate the implementation of the Local Exhaust Ventilation System in the AAS room. Method: This study used a descriptive observational method with a cross-sectional approach. It was carried out at the Testing Laboratory of the Technical Implementation Unit (henceforth-UPT) of Occupational Safety Surabaya. Data collection was carried out through direct observation in the field to determine the LEV system components and to measure the flow velocity in the inlet and outlet areas of the LEV system. The data obtained were analyzed descriptively by describing the situation systematically and factually. The data were then presented in the form of narration, tabulation, and figures. Results: The conditions of the Local Exhaust Ventilation (LEV), in terms of the design, type and material of each component such as the hood, ducting system and pump machine as well as the fan, are already in accordance with the tool specifications and ASHRAE standards. However, the LEV system has not installed an air cleaner. The results of the measurement show that flow velocity in the LEV system has met the standard, which is 10 m/s with the danger of fume contaminants. In fact, its volumetric flow rate has decreased by more than 20%. Conclusion: laboratory management is advised to consider installing an air cleaner on the LEV system installed in the Hitachi AAS so that contaminants released in the air are cleaner and more environmentally friendly.Keywords: hazard control, laboratory, local exhaust ventilation, ventilation

97/03169 The demise of the primary-secondary pumping paradigm for chilled water plant design

Chapter 6 - Commissioning, control, and maintenance of ventilation systems

Objective:Silicosis as an incurable occupational disease is common in industries and processes that contain silica dust. Since engineering controls can reduce the risk of silicosis, the goal of this study was to design, implement and evaluate industrial ventilation systems and filtration for silica dust, which is emitted from hydrocone crusher and screener units in a mineral processing company.Methods:In this project, local exhaust ventilation (LEV) system was designed and installed using the standard and valid guidelines. The dust concentration was measured in two stages before and after installation of the ventilation system in the workplace, silica emission sources and also in the workers' inhalation area. Finally, the efficiency of the system was determined.Results:The efficiency of LEV system in reducing workplace dust concentration and dust emission sources was 79.8% and 84.92% respectively. Furthermore, the efficiency of system in reducing the Respirable Crystalline Silica (RCS) at the worker's inhalation area was 92.13%. The collection efficiency of filtration system for total particles was 99.67 %.Conclusion:The results indicate that with designation and installation of the local exhaust ventilation (LEV) system and also installation of bag filter to collect dust, the concentration of dust in the workplace and in the inhalation area of workers has decreased significantly. As a result, this system can be used to control dust in similar industries.

Not every ventilation system performs as intended; much can be learned when they do not. The purpose of this study was to compare observed initial performance to expected levels for three saw-reconditioning shop ventilation systems and to characterize the changes in performance of the systems over a one-year period. These three local exhaust ventilation systems were intended to control worker exposures to cobalt, cadmium, and chromium during wet grinding, dry grinding, and welding/brazing activities. Prior to installation the authors provided some design guidance based on Industrial Ventilation, a Manual of Recommended Practice. However, the authors had limited influence on the actual installation and operation and no line authority for the systems. In apparent efforts to cut costs and to respond to other perceived needs, the installed systems deviated from the specifications used in pressure calculations in many important aspects, including adding branch ducts, use of flexible ducts, the choice of fans, and the construction of some hoods. After installation of the three systems, ventilation measurements were taken to determine if the systems met design specifications, and worker exposures were measured to determine effectiveness. The results of the latter will be published as a companion article. The deviations from design and maintenance failures may have adversely affected performance. From the beginning to the end of the study period the distribution of air flow never matched the design specifications for the systems. The observed air flows measured within the first month of installation did not match the predicated design air flows for any of the systems, probably because of the differences between the design and the installed system. Over the first year of operation, hood air flow variability was high due to inadequate cleaning of the sticky process materials which rapidly accumulated in the branch ducts. Poor distribution of air flows among branch ducts frequently produced individual hood air flows that were far below specified design levels even when the total air flow through that system was more than adequate. To experienced practitioners, it is not surprising that deviations from design recommendations and poor maintenance would be associated with poor system performance. Although commonplace, such experiences have not been documented in peer-reviewed publications to date. This publication is a first step in providing that documentation.

Drilling large holes (e.g., 10–20 mm diameter) into concrete for structural upgrades to buildings, highways, bridges, and airport runways can produce concentrations of respirable silica dust well above the ACGIH® Threshold Limit Value (TLV® = 0.025 mg/m3). The aim of this study was to evaluate a new method of local exhaust ventilation, hollow bit dust extraction, and compare it to a standard shroud local exhaust ventilation and to no local exhaust ventilation. A test bench system was used to drill 19 mm diameter x 100 mm depth holes every minute for one hour under three test conditions: no local exhaust ventilation, shroud local exhaust ventilation, and hollow bit local exhaust ventilation. There were two trials for each condition. Respirable dust sampling equipment was placed on a “sampling” mannequin fixed behind the drill and analysis followed ISO and NIOSH methods. Without local exhaust ventilation, mean respirable dust concentration was 3.32 (± 0.65) mg/m3 with a quartz concentration of 16.8% by weight and respirable quartz dust concentration was 0.55 (± 0.05) mg/m3; 22 times the ACGIH TLV. For both LEV conditions, respirable dust concentrations were below the limits of detection. Applying the 16.8% quartz value, respirable quartz concentrations for both local exhaust ventilation conditions were below 0.007 mg/m3. There was no difference in respirable quartz dust concentrations between the hollow bit and the shroud local exhaust ventilation systems; both were below the limits of detection and well below the ACGIH TLV. Contractors should consider using either local exhaust ventilation method for controlling respirable silica dust while drilling into concrete.

The analysis of the features of Orthodox churches, temples and cathedrals, elements of the design of the halls of worship, and their preservation. The types of hazards generated during the burning of candles and the parishioners and staff present are systematized. Thermal imaging surveys of convective flows formed during candle combustion were carried out. A technique for conducting experiments and a diagram of an experimental setup for measuring the temperature and air velocity in a convective jet have been developed. The diagram of the convective flow structure is presented, which consists of individual jets from each candle. The results of the study have been obtained, which make it possible to determine the area of stable convective flow and the place of installation of the exhaust hood above the candlestick, as well as the distance between the burning candles and the edge of the bottom of the umbrella. A local mechanical exhaust ventilation system with umbrellas has been developed to trap and remove harmful substances from the worship hall and provide comfortable conditions for parishioners and preserve the decoration elements of the halls. The characteristics and conditions for the efficient operation of the hoods in the local exhaust ventilation system and the factors influencing their operation are given.

시멘트 포장공정에서 발생하는 비산분진을 효율적으로 제거하기 위해 3가지 환기방식(국소배기시스템, 정전식스크러버시스템, 국소급기시스템)을 도입하고 풍량을 변화시키며 총 9가지의 조건에서 실험을 수행하였다. 분진의 농도는 시멘트분진 입자분포 특성을 고려하여 PM2.5, PM10, TSP로 구분하여 측정하였다. 3가지 환기방식에 대한 집진효율을 분석한 결과, 기존의 국소배기시스템과 정전식스크러버시스템이 같이 사용되는 경우 가장 효율적인 것으로 나타났다. 또한 정정식스크러버시스템의 풍량 증가에 따른 입자의 질량농도감소율이 큰 차이가 없는 것을 확인할 수 있었고 이로부터 정정식스크러버시스템을 <TEX>$2,700m^3/h$</TEX> 풍량으로 운전하는 것이 에너지절약 관점에서 효율적인 것이라고 판단되었다. 각 환기방식별 환기성능을 국소배기시스템의 풍량으로 환산한 결과, 대체시스템(정전식스크러버시스템, 국소급기시스템)분진제거성능이 우수한 젓으로 나타났고 정전식스크러버시스템이 국소급기시스템보다 상당히 효율적인 것으로 나타났다. 따라서 기존의 국소배기시스템파 정전식스크러버시스템을 동시에 가동한다면 국소배기시스템의 풍량만을 증가시키는 경우에 비해 반송동력을 줄일 수 있어 분진제거와 에너지절감측면에서 훨씬 효율적이라는 것을 알 수 있었다. We performed the experimental study on the control of suspended dust in a cement packaging process for various ventilation systems. To effectively remove the dust generated in the cement packaging process, three different kinds of ventilation system, such as local exhaust ventilation, electrostatic scrubber, and local air supply system, were adopted. Dust concentrations in the packaging process were measured with the variation of the airflow rate of the ventilation systems and then their ventilation performance were evaluated. From the results, we knew that the ventilation performance was the best when the local exhaust ventilation and the electrostatic scrubber were simultaneously operated in the packaging process. In the electrostatic scrubber system, the effect of the airflow rate on the indoor dust removal efficiency was negligible so hat he system ust be operated at <TEX>$2,700m^3/h$</TEX> for saving power consumption.

Ventilation is used to control indoor air quality for maintaining the health and performance of human and ensuring healthy environment. It is known that the environmental criteria are dictated by temperature, humidity, and contamination. In a case study at XY company, questionnaires were distributed to the workers and interviews were conducted to find out the level of satisfaction on working conditions in certain areas. 70% respondents reported feeling uncomfortable because of heat, dust and hot environment. An analysis of indoor air quality was carried out to measure the temperature at pouring area. Based on the analysis, the range of temperatures is from 35°C to 43°C. A local exhaust ventilation (LEV) system was design for improve indoor air quality and reduce extreme heat. The LEV system was proposed for the pouring area to capture then discharged heat or contaminants through a series of strategically placed overhead ducts.