The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Rong Fung Huang - One of the best experts on this subject based on the ideXlab platform.
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Influence of high heat load on flow and containment of an inclined air-curtain (IAC) Fume Hood
Journal of Occupational and Environmental Hygiene, 2018Co-Authors: Rong Fung HuangAbstract:ABSTRACTThe inclined air-curtain (IAC) Fume Hood has been reported to have “almost null leakage”[1] at low suction flow rates when operated at regular temperatures. However, previous research has not investigated the performance or optimized operating parameters when a high heat load is used in the IAC Fume Hood. For the present work, the effects of a high heat load on the flow field and contaminant leakage characteristics of the IAC Fume Hood were examined. The heat load was supplied to an IAC Hood according to the standard method of EN14175-7:2012. The laser-assisted smoke flow visualization technique was employed to identify the characteristic flow patterns. The standard tracer-gas concentration test method (EN14175-3:2003) was used to examine the leakage levels of the IAC Fume Hood under static conditions, sash movement, and simulated walk-by conditions. When the IAC Fume Hood was operated at a high heat load, the static test results showed negligibly small leakage levels at a face velocity greater th...
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effects of boundary layer separation controllers on a desktop Fume Hood
Journal of Occupational and Environmental Hygiene, 2016Co-Authors: Rong Fung Huang, Jiakun Chen, Shuofu HungAbstract:ABSTRACTA desktop Fume Hood installed with an innovative design of flow boundary-layer separation controllers on the leading edges of the side plates, work surface, and corners was developed and characterized for its flow and containment leakage characteristics. The geometric features of the developed desktop Fume Hood included a rearward offset suction slot, two side plates, two side-plate boundary-layer separation controllers on the leading edges of the side plates, a slanted surface on the leading edge of the work surface, and two small triangular plates on the upper left and right corners of the Hood face. The flow characteristics were examined using the laser-assisted smoke flow visualization technique. The containment leakages were measured by the tracer gas (sulphur hexafluoride) detection method on the Hood face plane with a mannequin installed in front of the Hood. The results of flow visualization showed that the smoke dispersions induced by the boundary-layer separations on the leading edges of...
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Development and Characterization of an Inclined Air-Curtain (IAC) Fume Hood
Annals of Occupational Hygiene, 2015Co-Authors: Rong Fung Huang, Jiakun Chen, Kun-chi TangAbstract:An inclined air-curtain (IAC) Fume Hood was developed and characterized using the laser-assisted smoke flow visualization technique and tracer-gas (sulphur hexafluoride) concentration detection method. The IAC Fume Hood features four innovative design elements: (i) an elongated suction slot installed at the Hood roof with an offset towards the rear wall, (ii) an elongated up-blowing planar jet issued from the work surface near the Hood inlet, (iii) two deflection plates installed at the left and right side walls, and (iv) a boundary-layer separation controller installed at the sash bottom. Baffles employed in conventional Hoods were not used. The suction slot and the up-blowing planar jet formed a rearward-inclined push-pull air curtain. The deflection plates worked with the inclined air curtain to induce four rearward-inclined counter-rotating 'tornados.' The Fumes generated in the Hood were isolated behind the rearward-inclined air curtain, entrained by the low pressure within the vortical flows, moved up spirally, and finally exhausted through the suction slot. The risk of containment leakage due to the large recirculation vortex that usually exists behind the sash of conventional Hoods was reduced by the boundary-layer separation controller. The results of the tracer-gas concentration detection method based on the EN-14175 method showed that the flow field created by the geometric configurations of the IAC Hood presented characteristics of low leakage and high resistance to dynamic disturbances at low face velocities. The leakage levels measured by the static, sash movement, and walk-by tests were negligible at a face velocity of 0.26 m s(-1).
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Flow and Leakage Characteristics of a Sashless Inclined Air-Curtain (sIAC) Fume Hood Containing Tall Pollutant-Generation Tanks
Journal of Occupational and Environmental Hygiene, 2013Co-Authors: Jiakun Chen, Rong Fung Huang, Wei-lun HungAbstract:In many Fume Hood applications, pollutant-generation devices are tall. Human operators of a Fume Hood must stand close to the front of the Hood and lift up their hands to reach the top opening of the tall tank. In this situation, it is inconvenient to access the conventional Hood because the sash acts as a barrier. Also, the bluff-body wake in front of the operator's chest causes a problem. By using laser-assisted smoke flow visualization and tracer-gas test methods, the present study examines a sashless inclined air-curtain (sIAC) Fume Hood for tall pollutant-generation tanks, with a mannequin standing in front of the Hood face. The configuration of the sIAC Fume Hood, which had the important element of a backward-inclined push-pull air curtain, was different from conventional configurations. Depending on suction velocity, the backward-inclined air curtain had three characteristic modes: straight, concave, and attachment. A large recirculation bubble covering the area—from the Hood ceiling to the work su...
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Flow and Containment Characteristics of a Sash-less, Variable-Height Inclined Air-Curtain Fume Hood
Annals of Occupational Hygiene, 2013Co-Authors: Rong Fung Huang, Jiakun Chen, Wei-lun HungAbstract:To increase containment efficiency and reduce energy consumption, a sash-less, variable-height inclined air-curtain Fume Hood (sIAC Hood) was developed and tested by a laser-assisted flow visualization technique and tracer-gas detection method. This novel design requires neither sash nor baffle. The sIAC Hood employed the inclined push-pull air-curtain technique and two deflection plates installed on the side walls of the Hood to induce a tetra-vortex flow structure. The results of flow visualization showed that the slot for suction flow, offset from the slot for the up-blowing jet, caused the air curtain to incline towards the rear wall, thus enhancing the robustness of the tetra-vortex flow structure. Such a flow structure could reduce the influence of draught and human walk-by across the Hood face. The containment around the central area of the Hood was isolated by the inclined push-pull air curtain. The pollutants carried by the reverse flow induced by the flow separation were guided by the deflection plates from the side walls towards the rear, thus contributing to the formation of the tetra-vortex flow structure. The up/down movable ceiling positioned the suction slot close to the device's pollutant emission opening, but left room (less than 50 cm) for unrestricted hand movement. Testing was carried out based on the methodology described in EN14175. The results of a static test showed that small face velocities of 0.25 and 0.16 m s(-1) were enough to obtain nearly null leakage levels for low and tall pollutant sources. The results of a traversing plate test showed that the face velocity, 0.32 m s(-1), would cause negligibly small leakage levels. The sIAC Hood could obtain significantly higher containment efficiency than a conventional Hood by operating at a face velocity significantly lower than that of conventional Hoods.
Jiakun Chen - One of the best experts on this subject based on the ideXlab platform.
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effects of boundary layer separation controllers on a desktop Fume Hood
Journal of Occupational and Environmental Hygiene, 2016Co-Authors: Rong Fung Huang, Jiakun Chen, Shuofu HungAbstract:ABSTRACTA desktop Fume Hood installed with an innovative design of flow boundary-layer separation controllers on the leading edges of the side plates, work surface, and corners was developed and characterized for its flow and containment leakage characteristics. The geometric features of the developed desktop Fume Hood included a rearward offset suction slot, two side plates, two side-plate boundary-layer separation controllers on the leading edges of the side plates, a slanted surface on the leading edge of the work surface, and two small triangular plates on the upper left and right corners of the Hood face. The flow characteristics were examined using the laser-assisted smoke flow visualization technique. The containment leakages were measured by the tracer gas (sulphur hexafluoride) detection method on the Hood face plane with a mannequin installed in front of the Hood. The results of flow visualization showed that the smoke dispersions induced by the boundary-layer separations on the leading edges of...
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installation of a flow control device in an inclined air curtain Fume Hood to control wake induced exposure
Journal of Occupational and Environmental Hygiene, 2016Co-Authors: Jiakun ChenAbstract:ABSTRACTAn inclined plate for flow control was installed at the lower edge of the sash of an inclined air-curtain Fume Hood to reduce the effects of the wake around a worker standing in front of the Fume Hood. Flow inside the Fume Hood is controlled by the inclined air-curtain and deflection plates, thereby forming a quad-vortex flow structure. Controlling the face velocity of the Fume Hood resulted in convex, straight, concave, and attachment flow profiles in the inclined air-curtain. We used the flow visualization and conducted a tracer gas test with a mannequin to determine the performance of two sash geometries, namely, the half-cylinder and inclined plate designs. When the half-cylinder design was used, the tracer gas test registered a high leakage concentration at Vf ≦ 57.1 fpm or less. This concentration occurred at the top of the sash opening, which was close to the breathing zone of the mannequin placed in front of the Fume Hood. When the inclined plate design was used, the containment was good, ...
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Development and Characterization of an Inclined Air-Curtain (IAC) Fume Hood
Annals of Occupational Hygiene, 2015Co-Authors: Rong Fung Huang, Jiakun Chen, Kun-chi TangAbstract:An inclined air-curtain (IAC) Fume Hood was developed and characterized using the laser-assisted smoke flow visualization technique and tracer-gas (sulphur hexafluoride) concentration detection method. The IAC Fume Hood features four innovative design elements: (i) an elongated suction slot installed at the Hood roof with an offset towards the rear wall, (ii) an elongated up-blowing planar jet issued from the work surface near the Hood inlet, (iii) two deflection plates installed at the left and right side walls, and (iv) a boundary-layer separation controller installed at the sash bottom. Baffles employed in conventional Hoods were not used. The suction slot and the up-blowing planar jet formed a rearward-inclined push-pull air curtain. The deflection plates worked with the inclined air curtain to induce four rearward-inclined counter-rotating 'tornados.' The Fumes generated in the Hood were isolated behind the rearward-inclined air curtain, entrained by the low pressure within the vortical flows, moved up spirally, and finally exhausted through the suction slot. The risk of containment leakage due to the large recirculation vortex that usually exists behind the sash of conventional Hoods was reduced by the boundary-layer separation controller. The results of the tracer-gas concentration detection method based on the EN-14175 method showed that the flow field created by the geometric configurations of the IAC Hood presented characteristics of low leakage and high resistance to dynamic disturbances at low face velocities. The leakage levels measured by the static, sash movement, and walk-by tests were negligible at a face velocity of 0.26 m s(-1).
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Flow and Leakage Characteristics of a Sashless Inclined Air-Curtain (sIAC) Fume Hood Containing Tall Pollutant-Generation Tanks
Journal of Occupational and Environmental Hygiene, 2013Co-Authors: Jiakun Chen, Rong Fung Huang, Wei-lun HungAbstract:In many Fume Hood applications, pollutant-generation devices are tall. Human operators of a Fume Hood must stand close to the front of the Hood and lift up their hands to reach the top opening of the tall tank. In this situation, it is inconvenient to access the conventional Hood because the sash acts as a barrier. Also, the bluff-body wake in front of the operator's chest causes a problem. By using laser-assisted smoke flow visualization and tracer-gas test methods, the present study examines a sashless inclined air-curtain (sIAC) Fume Hood for tall pollutant-generation tanks, with a mannequin standing in front of the Hood face. The configuration of the sIAC Fume Hood, which had the important element of a backward-inclined push-pull air curtain, was different from conventional configurations. Depending on suction velocity, the backward-inclined air curtain had three characteristic modes: straight, concave, and attachment. A large recirculation bubble covering the area—from the Hood ceiling to the work su...
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Flow and Containment Characteristics of a Sash-less, Variable-Height Inclined Air-Curtain Fume Hood
Annals of Occupational Hygiene, 2013Co-Authors: Rong Fung Huang, Jiakun Chen, Wei-lun HungAbstract:To increase containment efficiency and reduce energy consumption, a sash-less, variable-height inclined air-curtain Fume Hood (sIAC Hood) was developed and tested by a laser-assisted flow visualization technique and tracer-gas detection method. This novel design requires neither sash nor baffle. The sIAC Hood employed the inclined push-pull air-curtain technique and two deflection plates installed on the side walls of the Hood to induce a tetra-vortex flow structure. The results of flow visualization showed that the slot for suction flow, offset from the slot for the up-blowing jet, caused the air curtain to incline towards the rear wall, thus enhancing the robustness of the tetra-vortex flow structure. Such a flow structure could reduce the influence of draught and human walk-by across the Hood face. The containment around the central area of the Hood was isolated by the inclined push-pull air curtain. The pollutants carried by the reverse flow induced by the flow separation were guided by the deflection plates from the side walls towards the rear, thus contributing to the formation of the tetra-vortex flow structure. The up/down movable ceiling positioned the suction slot close to the device's pollutant emission opening, but left room (less than 50 cm) for unrestricted hand movement. Testing was carried out based on the methodology described in EN14175. The results of a static test showed that small face velocities of 0.25 and 0.16 m s(-1) were enough to obtain nearly null leakage levels for low and tall pollutant sources. The results of a traversing plate test showed that the face velocity, 0.32 m s(-1), would cause negligibly small leakage levels. The sIAC Hood could obtain significantly higher containment efficiency than a conventional Hood by operating at a face velocity significantly lower than that of conventional Hoods.
Michael J Ellenbecker - One of the best experts on this subject based on the ideXlab platform.
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Effects of work practices and upper body movements on the performance of a laboratory Fume Hood
Journal of Chemical Health and Safety, 2016Co-Authors: Michael J Ellenbecker, Susan R Woskie, L DiberardinisAbstract:A Hood user's work practices and upper body movements can adversely affect the performance of a laboratory Fume Hood. To quantify the possible effects, Hood performance was measured while simulating typical user activities scenarios. The tested variables were two sash opening heights, two Hood clutter settings, two thermal loads, and three hand–arm–trunk motions, totaling 24 (2 × 2 × 2 × 3) different test conditions. Hood face velocity was maintained at 0.5 m/s for all tests, using a fan speed controller. For each test condition, the Hood's performance was evaluated using the ASHRAE 110-1995 tracer gas test method. Duplicate measurements were made for each condition, so that a total of 48 tests were conducted, in random order. Three-way ANOVA was performed to find significant effects of work practices and upper body movements on breathing concentrations. The degree of sash opening was the most significant factor affecting Hood performance, followed by hand–arm–trunk motions and thermal load. The effect of Hood clutter was not statistically significant, but the interaction effect with other factors was. The highest breathing concentration value occurred during the test with the sash fully open, arms-down posture, thermal load present, and Hood clutter present. These conditions created complex airflow patterns inside the Hood that resulted in leakage into the breathing zone. Although the test conditions were limited, the results of this study suggest that good work practices in combination with good Hood design and adequate face velocity can significantly reduce worker exposure. Reducing sash height while working in front of a laboratory Fume Hood is vital to reducing potential exposure to the air contaminant generated inside the Hood.
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A new quantitative method for testing performance of in-use laboratory chemical Fume Hoods
Journal of Chemical Health and Safety, 2016Co-Authors: Michael J Ellenbecker, Susan R Woskie, L DiberardinisAbstract:The American Society of Heating and Air-Conditioning Engineers (ASHRAE) 110-1995 tracer gas test method is a well-established measure of laboratory chemical Hood performance, but it requires expensive equipment and trained personnel. This study proposes a new quantitative method for testing laboratory chemical Fume Hood performance using materials commonly found in laboratories. The method uses dry ice and warm water to generate visible fog and carbon dioxide (CO2) gas, and then measures chemical Fume Hood leakage with a CO2 detector. The fog can also be used as a visual aid to train workers in proper Hood use. To compare the new method with the ASHRAE 110-1995 tracer gas method, both were used to test a conventional by-pass laboratory chemical Fume Hood under eight typical use conditions (comprised of different sash opening heights, thermal loads, and Hood clutter). Average Hood face velocity was maintained at 0.5 m/s (100 ft/min) ± 1% throughout all tests. The test results of the new method were comparable to those of the ASHRAE 110-1995 method. A significant regression equation was found in this study (F(1,6) = 36.15, p = 0.001), with R2 of 0.858: SF6 breathing concentration (in ppb) is equal to −118.184 + 0.912 × CO2 leakage values (in ppm). Using this regression equation, CO2 leakage can be used to estimate SF6 breathing zone concentrations. Ultimately, the new method is cheaper and easier to use than the ASHRAE 110-1995 method for routine Hood performance evaluation.
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Evaluation of leakage from Fume Hoods using tracer gas, tracer nanoparticles and nanopowder handling test methodologies.
Journal of Occupational and Environmental Hygiene, 2014Co-Authors: Kevin H. Dunn, Susan R Woskie, Candace Su-jung Tsai, James S. Bennett, Alberto Garcia, Michael J EllenbeckerAbstract:The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical Fume Hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside Fume Hoods. This study evaluated the performance of a new commercially available nano Fume Hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the Hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the Hood opening. These containment tests were conducted across a range of Hood face velocities (60, 80, and 100 ft/min) and with the room ventilation system tur...
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Airborne Nanoparticle Exposures while Using Constant-Flow, Constant-Velocity, and Air-Curtain-Isolated Fume Hoods
Annals of Occupational Hygiene, 2009Co-Authors: Su-jung Tsai, Rong Fung Huang, Michael J EllenbeckerAbstract:Tsai et al. (Airborne nanoparticle exposures associated with the manual handling of nanoalumina and nanosilver in Fume Hoods. J Nanopart Res 2009; 11: 147–61) found that the handling of dry nanoalumina and nanosilver inside laboratory Fume Hoods can cause a significant release of airborne nanoparticles from the Hood. Hood design affects the magnitude of release. With traditionally designed Fume Hoods, the airflow moves horizontally toward the Hood cupboard; the turbulent airflow formed in the worker wake region interacts with the vortex in the constant-flow Fume Hood and this can cause nanoparticles to be carried out with the circulating airflow. Airborne particle concentrations were measured for three Hood designs (constant-flow, constant-velocity, and air-curtain Hoods) using manual handling of nanoalumina particles. The Hood operator’s airborne nanoparticle breathing zone exposure was measured over the size range from 5 nm to 20 mm. Experiments showed that the exposure magnitude for a constant-flow Hood had high variability. The results for the constant-velocity Hood varied by operating conditions, but were usually very low. The performance of the air-curtain Hood, a new design with significantly different airflow pattern from traditional Hoods, was consistent under all operating conditions and release was barely detected. Fog tests showed more intense turbulent airflow in traditional Hoods and that the downward airflow from the double-layered sash to the suction slot of the air-curtain Hood did not cause turbulence seen in other Hoods.
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a review of published quantitative experimental studies on factors affecting laboratory Fume Hood performance
Journal of Occupational and Environmental Hygiene, 2008Co-Authors: Susan R Woskie, L Diberardinis, Michael J EllenbeckerAbstract:This study attempted to identify the important factors that affect the performance of a laboratory Fume Hood and the relationship between the factors and Hood performance under various conditions by analyzing and generalizing the results from other studies that quantitatively investigated Fume Hood performance. A literature search identified 43 studies that were published from 1966 to 2006. For each of those studies, information on the type of test methods used, the factors investigated, and the findings were recorded and summarized. Among the 43 quantitative experimental studies, 21 comparable studies were selected, and then a meta-analysis of the comparable studies was conducted. The exposure concentration variable from the resulting 617 independent test conditions was dichotomized into acceptable or unacceptable using the control level of 0.1 ppm tracer gas. Regression analysis using Cox proportional hazards models provided Hood failure ratios for potential exposure determinants. The variables that wer...
Jan Melin - One of the best experts on this subject based on the ideXlab platform.
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required response time for variable air volume Fume Hood controllers
Annals of Occupational Hygiene, 2000Co-Authors: Lars Ekberg, Jan MelinAbstract:This paper describes results from tests made with the aim of investigating how quickly the exhaust air flow rate through Fume Hoods needs to be controlled in order to prevent contaminants from leaking out of the Fume Hood and putting the safety of the laboratory personnel at risk. The measurements were made on a laboratory Fume Hood in a chemical laboratory. There were no other Fume Hoods in the laboratory, and the measurements were made without interference from persons entering or leaving the laboratory or walking about in it. A tracer gas method was used with the concentration of dinitrogen oxide (N2O) being recorded by a Foxboro Miran 101 infra-red gas analyser. In parallel with the tracer gas measurements, the air velocity through the face opening was also measured, as was the control signal to the damper controlling the air flow rate. The measurements show an increased outward leakage of tracer gas from the Fume Hood if the air flow rate is not re-established within 1‐2 s after the sash is opened. If the delay exceeds 3 s the safety function is temporarily defeated. The measurements were made under virtually ideal conditions. Under more typical conditions, the Fume Hood could be exposed to various other external perturbations, which means that the control system should re-establish the correct exhaust flow more quickly than indicated by the measurement results obtained under these almost ideal conditions. # 2000 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.
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Measurements and Analyses of the Performancs of Laboratory Fume Hoods
1997Co-Authors: Jan MelinAbstract:When working with health-hazardous substances or unpleasant airborne pollutants, it is important to have ventilation systems that are designed and operated to protect persons working in the laboratory. In laboratory applications, the Fume Hood is the most commonly used item of protective equipment. This thesis is concerned with the air-handling aspects of the protective function of laboratory Fume Hoods. In order to be certain that a laboratory Fume Hood is providing adequate protection, so that users are not exposed to health-hazardous substances, it is necessary to check its performance. There are a number of ways of doing this, but the most commonly employed method for quantitative evaluation of Fume Hood performance is to meter a tracer gas inside the Fume Hood and measure the outward leakage with an IR analyser. Measurements presented in the thesis show that outward leakage from a Fume Hood has a very rapid, pulsed characteristic. Since the IR analysers that are normally used when checking the performance of a Fume Hood do not have sufficiently rapid response, this means that the recorded outward leakage does not fully reflect the actual leakage. In the thesis, theoretical relationships are presented that describe the inertia of IR analysers, and calculations for short-duration pulses and normal instrument time constants show that the gas concentration recorded by the instruments differ considerably from the true gas concentration. The thesis describes two methods of determining the actual characteristic of the outward leakage from a Fume Hood. One method is based on a derived relationship that estimates the true gas concentration on the basis of the recorded concentration. The other way of determining the actual outward leakage process is to use a newly developed instrument with negligible inertia. The measurements that were made with this instrument clearly show that the outward leakage from a Fume Hood is pulsed, and that the pulses are of considerably shorter duration and have higher peak values than had previously been possible to record with traditional IR instruments. In the thesis, results are also presented from measurements with the aim of determining how fast the flow needs to be adjusted after the position of the Hood sash is changed in order to prevent outward leakage. These measurements indicate that the air flow rate should be adjusted and stabilized within 3-4 seconds in order to avoid outward leakage. Further, in order to investigate whether flow variations in the exhaust air system could affect the performance of a Fume Hood, measurements were made in a test room. The results show that if there are oscillations in the exhaust air system while someone is in front of the Fume Hood, unstable air flow through the Hood occurs, sufficient to create outward leakage.
Edward L. Gershey - One of the best experts on this subject based on the ideXlab platform.
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Fume Hood Performance: Using a Bypass in Variable Air Volume Systems
Applied Occupational and Environmental Hygiene, 1998Co-Authors: Richard V. Joao, E. Party, Edward L. GersheyAbstract:Abstract Variable air volume (VAV) exhaust systems provide sophisticated engineering controls for maintaining laboratory ventilation. Depending on how they are installed, they may be very responsive to changes in air flows and air pressures. Some of these changes are a consequence of natural phenomena and some are induced by the transit and actions of laboratory occupants. While the responsiveness of VAV controls can provide tight regulation, the dynamic nature of the VAV system may also introduce undesirable air flow fluctuations. Further-more, since the volumes of air being exhausted vary, the amount of air available for Fume Hood capture and containment will also vary. These studies examine the responsiveness and consequences of ventilation system perturbations, as well as the effect of Fume Hood exhaust being reduced to very low air volumes. Face velocity and air volumes were measured at different sash heights and in response to rapid sash movements. In addition, capture of contaminants was evaluated ...
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Fume Hood performance: Face velocity variability inconsistent air volume systems
Applied Occupational and Environmental Hygiene, 1998Co-Authors: Catherine E. Volin, James Reiman, Richard V. Joao, E. Party, Edward L. GersheyAbstract:Abstract A 3-year survey of 366 bench-type Fume Hoods in working laboratories in conventional, constant air volume settings showed that face velocities varied greatly from unit to unit and over time. Fume Hoods with bypasses performed better than those without; however, even newly fabricated bypass Hoods exhibited large variations (i.e., 60 to 200 ft/min, across the face). These variations were due to several factors; however, face velocities at 100 ± 10 ft/min at working sash heights in the range of 20 to 40 cm (8 to 16 inches) were attainable. The use of “smoke” showed poor containment, especially at face velocities below 85 ft/min (0.425 m/s) or above 130 ft/min (0.65 m/s) and when the Hoods were obstructed by large items placed on the work surface. Auxiliary/supplemental air created unstable face velocities and poor smoke patterns. The analysis of 3 years of Fume Hood monitoring showed clearly the need for and importance of a maintenance program where the Fume Hood lower slots are cleaned and fans, du...
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Fume Hood Performance: Slot Settings and Containment Testing
Applied Occupational and Environmental Hygiene, 1998Co-Authors: James Reiman, Richard V. Joao, Catherine E. Volin, John S. Fernandez, E. Party, Edward L. GersheyAbstract:Abstract Fume Hoods are provided with adjustable upper, lower, and sometimes middle slots. Slot adjustments affect the fraction of air exhausted through the different slots, which in part can determine the concentration of contaminants in different strata within the Hood. Since Fume Hoods are used to contain particulate aerosols and chemical vapors, dioctylphthalate (DOP) and sulfur hexafluoride were used as surrogates to evaluate the effect of slot settings and sash heights on aerosol and vapor containment. While slot position had little effect on the release of sulfur hexafluoride outside the Fume Hood, opening the upper slot from 1.25 cm (0.5 inches) to 5 cm (2 inches) increased the release of DOP tenfold to thirtyfold depending on sash height. In a variable air volume Hood, lowering the sash height decreased the total volume of air exhausted and increased the contaminant (DOP) concentration inside the Fume Hood. A narrow upper slot and wide lower slot were found to be optimal, while the practice of lo...
