Local Exhaust Research Articles

Assessment of occupational exposure to micro/nano particles generated from carbon fiber-reinforced plastic processing.

Carbon fiber-reinforced plastics (CFRP) are leading functional materials with superior strength and low mass density compared to metal. Our previous factory site analyses found that CFRP processing generates fibrous debris and fine micro/nano-sized particles of various shapes. The present interventional study was conducted at a factory located in Japan and evaluated debris consisting of various-sized particles generated during the industrial processing of CFRP, such as cutting, grinding, and turning of CFRP pipes, using real-time particle monitoring devices of the following: PM4 Digital Dust Monitor (DDM), handled Optical Particle Counter (OPC), Condensation Particle Counter (CPC), and Scanning Mobility Particle Sizer (SMPS). In addition, personal exposure of workers was evaluated using a novel wearable PM2.5-compatible device (P-sensor). First, we confirmed the presence of micro/nano particles in the dust generated during industrial processing of CFRP. Finer CFRP-generated particles were detected by the nanoparticle-compatible devices; CPC and SMPS, but not by OPC or DDM. The dynamic detection pattern of the P-sensor resembled that recorded by the nanoparticle-compatible devices. The novel wearable P-sensor can be used to measure finer particles generated by CFRP processing in occupational settings. Second, the exposure assessment was conducted twice and the levels of the micro/nano particles in the second survey were significantly (less than half) lower than that in the first survey. By avoiding immediate power-off of the exhaust system after operations, the scattering of particles was effectively reduced. Our results indicate that effective use of local exhaust ventilation system improves the workplace environment for particle exposure.

Evaluating Occupational Workforce and Practices in New York Metropolitan Nail Salons.

This study investigated workforce characteristics, work practices, protective measures, and health symptoms among nail salon workers in New York and New Jersey following the implementation of local exhaust ventilation (LEV) regulations in New York. An online survey conducted from 2022 to 2023 targeted registered nail salons and manicurists in both states (N = 146). The majority of respondents were Asian, primarily Korean (52.1%) and Chinese (26%). In New York, 79% of salons had a mechanical ventilation system, including LEV, while in New Jersey, where no ventilation regulation exists, only 52% of nail salons had mechanical ventilation systems. A substantial proportion of manicurists reported health-related concerns (40.5%) and symptoms related to chemical exposure (67.6%). The study emphasizes the need for continuous and improved illness prevention strategies, including the use of safer products, comprehensive health and safety training, and effective ventilation practices, to better protect nail salon workers.

The potential of local exhaust combined with mixing and displacement ventilation systems to mitigate COVID-19 transmission risks

The performance of two types of air diffusers, a perforated duct and a low-velocity unit coupled with local exhausts, on airborne transmission and cross-infection was investigated in a meeting room. The effect of air diffusers’ locations on airborne transmission was investigated. Six local exhausts were installed above six workstations at 2.0 m height. Respiratory-generated airborne pathogens were simulated using SF6 in the exhaled air of the manikin acting as an infected person. The SF6 concentration in the inhaled air of five susceptible persons remained steady with perforated duct located on the ceiling and at 1.7 m height attached to the corridor wall, but fluctuated greatly when perforated duct were located on the floor, although with a much lower concentration level. The perforated duct under the warm window showed the best potential for mitigating airborne transmission. The concentration in the inhaled air was varied with horizontally supplied low-velocity unit, but much steadier with low-velocity unit at 1.7 m attached to the wall. With an adjusted airflow pattern from low-velocity unit, the inhaled concentration was much lower and uniform among the five susceptible persons. The contaminant removal effectiveness (CRE) was 4.3 with perforated duct under a warm window on the floor. With an adjusted airflow pattern from low-velocity unit, the CRE was much more consistent and increased from 2.1 to 3.9 with an airflow rate from 61 l/s to 116 l/s. The infection probability was the lowest with the perforated duct on the floor and adjusted low-velocity unit.

Reducing exposure levels of immersion washing workers to ortho-phthalaldehyde by improving exhaust systems.

The American Conference of Governmental Industrial Hygienists recommends a threshold limit value-ceiling (TLV-C) of 0.1ppb for occupational exposure to ortho-phthalaldehyde (OPA) used in washing endoscope probes. To adhere to this extremely low exposure limit, this case study aimed to reduce OPA exposure concentrations of workers during immersion washing of an endoscope probe body. This was achieved by attaching a new duct and hood to the existing ceiling exhaust system. The type of hood was determined by calculating and comparing the capture velocity obtained by assuming either an exterior or an enclosing hood. Additionally, the effect on improving the working environment was tested before and after the installation of the hood by measuring the OPA vapor concentration. The calculated capture velocities of the exterior and enclosing hoods were 0.05m/s and 0.19m/s, respectively. Considering the operability, the exterior hood was more appropriate; however, the calculated capture velocity indicated potential inadequacy in meeting the TLV-C requirement, leading to the adoption of the enclosing hood. The OPA vapor concentration in ceiling value measurements taken after the enclosing hood was fitted was reduced to 0.2ppb, that is, 1/10 of the original concentration. Although the environmental concentration after the improvement still exceeded the TLV-C of 0.1ppb, this study's findings indicate that even substances with extremely low occupational exposure limits can be managed with appropriate local exhaust ventilation.

Spray field characteristics and the effect of spray-local exhaust ventilation on the control of high-temperature buoyant jets

Process equipment limitations resulted in constraints on the location of the exhaust hood, which in turn caused escape of high-temperature buoyant jets. In response to this situation, spray system is installed as an auxiliary measure to improve the control effect by spray cooling and weakening the momentum. However, the correlation between spray parameters and its atomization characteristics in high temperature ambient is not clear, reasonable spray parameters directly affect the performance of spray-local exhaust ventilation (SLEV). In this study, we discuss the spray field characteristics under the action of high-temperature buoyant jets, the effects of exhaust and spray parameters on the capture efficiency of SLEV, combined with orthogonal test to get the optimization order. Influences discussed include: exhaust velocity, spray pressure, and nozzle hole diameter. The results showed that SLEV provides superior control of high-temperature buoyant jets, up to two times that of the local exhaust ventilation (LEV). Compared to nozzle hole diameter, the spray pressure significantly effects spray field characteristics. Under high-temperature buoyant jets conditions, the statistical mean diameter obeys a power function relationship with spray pressure, and the capture efficiency was 75% as the spray pressure of 2.0 MPa and nozzle hole diameter of 1.8 mm. The factors affecting the performance of SLEV were found to be exhaust velocity > spray pressure > nozzle hole diameter by range analysis. The research results are expected to contribute to the optimization and enhancement of the SLEV.

Flow-field characteristics of the thermal plume above an elliptical high-temperature heat source surface

The thermal plume formed by the high-temperature elliptical heat source surface during the smelting process is often captured and removed by the local exhaust system. Accurately mastering the flow-field characteristics of such high-temperature elliptical heat plumes is helpful for efficient design of local exhaust systems. In this paper, the effects of the ratio of long and short axes (5/4 ≤ ξ ≤ 5/1) and the intensity of heat source (80 ≤ F ≤ 160 W) on the axial and radial velocity distribution of thermal plume in an elliptical heat source are investigated by numerical simulation combined with experimental validation. The results show that in the range of ξ ≤ 5/1, the axial dimensionless velocity distribution of the elliptical plume field and the spreading range of the plume field are mainly affected by ξ instead of F. For 5/4 ≤ ξ ≤ 5/1, the maximum axial velocity Um appears at 1.7 to 2.7 times Z/L (plume height to heat source long axis ratio). For ξ ≤ 5/2, the height at which the cross-sectional velocity field transitions to a circular distribution aligns with the height of Um. It is found that the plume velocity field is characterized by applying the point source model for ξ ≤ 5/3, and vice versa for the linear source model. The plume flow rate formulation obtained by modifying the linear source model for ξ > 5/3 has a better predictive ability in the Z/L ≤ 5 region. This study provides a reference for the design of ventilation systems for elliptical surface heat sources.

Numerical and experimental studies of airflows at exhaust hoods with inlet extensions

Local exhaust ventilation is used to capture contaminants and maintain a comfortable atmosphere in premises. Exhaust hoods with extension units (canopy hoods) are commonly used in open-type local exhaust devices. The goal of this study was to use computational and experimental methods to determine the effect of adding an extension to a local exhaust hood on the separated-flow streamlines, vortex zones, exhaust velocity distribution, and local drag coefficient. We used the discrete vortex method together with computational fluid dynamics to investigate air flows near round and slotted extended exhaust hoods. We then compared the computed airflow velocity field, vortex zone outlines at the inlet of a local exhaust hood, and local drag coefficient factor with data from a field experiment. Outlines of vortex zones resulting from flow separation at the inlet of the hood were considered for a hood length of 5 times gauge (the radius of a round hood or half-width of a slotted exhaust hood), hood tilt angles of 90°, 75°, 60°, 45°, and 30°, and extension lengths of 0; 0.5; 1; and 2 times gauge. We found that longer extensions caused the first vortex zone to enlarge, and the contaminant capture velocity of the local exhaust hood to decrease. We identified the behavior of the local drag coefficient at various hood tilt angles, extension lengths (as listed above), and hood lengths (including 2, 3, and 5 times gauge), and translated them into equations for computing the local drag coefficient.

Analysis of Capture Velocity in the Case of Local Exhaust Ventilation

Analysis of Capture Velocity in the Case of Local Exhaust Ventilation

Improved aerodynamic performance of the exhaust hood with triple-faced flange

For a local exhaust ventilation system to trap contaminants effectively, it is highly important to minimize its energy consumption without forgoing efficiency. Energy savings can be achieved by reducing the aerodynamic drag of non-straight elements of local ventilation systems. Goal of the study is to minimize the drag of an exhaust with a triple-faced flange by varying shelves lengths and tilt angles by the method of coordinated descent. Study conducted numerically and experimentally. For the first time a pattern of changes in LDC value depending on the size of the shelves was revealed. The minimum value of LDC is reached when the length of the first shelf adjacent to the exhaust channel is 0.5l (l -half width of the slot or radius of round exhaust hood), the angle of its inclination is 30°; the length of the second shelf is 0.7l with an angle of inclination of 90°; the length of the third shelf is 0.2l with an angle of inclination of 120°. The found velocity distribution shows the effectiveness of the exhaust hood capture. The reduction of the LDC, when compared with the typical exhaust hood with the flange inclined on 90° was 76 %, and compared with a real industrial exhaust hood from the welding table – 65.7 %. The outline of vortex zones at the entrance to the exhaust hood was determined by different methods. The findings can be used for the design and development of energy-saving slotted and round exhaust hoods.

An Experimental Study on the Efficacy of Local Exhaust Systems for the Mitigation of Exhaled Contaminants in a Meeting Room

In industrial applications, local exhaust systems have been used extensively for capturing and confining contaminants at their source. The present study investigates the efficacy of these systems in mitigating the spread of exhaled pollutants by combining them with mixing and displacement ventilation. Experiments were conducted in a simulated meeting room with six closely situated workstations, featuring five exposed persons (simulated with heated dummies) and one infected person (simulated with a breathing manikin). Six overhead local exhaust units, merged with panels, corresponding to workstations, were installed using a lowered false ceiling. Additionally, a table plenum setting for air inlets was introduced to enhance displacement ventilation effectiveness along with local exhaust systems. Results from 16 experimental cases are presented, using the local air quality index and ventilation effectiveness in the breathing zone. The local exhaust system improved the local air quality at the measuring locations closest to the infector in almost all test scenarios. The improvement, particularly significant with displacement ventilation, marked a maximum 35% increase in the local air quality index adjacent to the infector and 25% in the entire breathing zone of the tested meeting room. Moreover, the table plenum settings, coupled with displacement ventilation, further enhanced conditions in the breathing zone. Under the specific conditions of this investigation, the number of operational local exhausts had a marginal impact on mixing ventilation but a significant one on displacement ventilation tests. The efficacy of local exhaust systems was also influenced by the levels of heat gains present in the room. Overall, the study aims to contribute to ongoing efforts to identify sustainable solutions to mitigate indoor airborne diseases with a combination of supply and local exhaust units.

Poultry evisceration and cross-contamination – Effectiveness of local air extraction and mechanical barriers

Poultry evisceration poses a risk of airborne carcass contamination with pathogens. While prior research has identified this hazard, ventilation strategies to mitigate it remain underexplored. This study employed computational fluid dynamics (CFD) simulations using Star-CCM+ software to evaluate the efficacy of local exhaust ventilation and mechanical barriers against airborne contamination. Particle deposition under various scenarios was assessed. The simulations demonstrated near-complete prevention of both direct and indirect airborne contamination with local exhaust ventilation. Mechanical barriers surrounding carcasses significantly reduced particle deposition (18–96%) on subsequent carcasses, although localized increases in contamination were observed in specific circumstances. Overall, implementing local exhaust ventilation and, to a lesser extent, mechanical barriers, shows promise for minimizing carcass contamination during poultry evisceration. These findings warrant further research to refine ventilation design and operational parameters for enhanced biosecurity in poultry processing facilities.

Investigation of Ventilation Performance to Improve the Indoor Air Quality of Institutional Kitchens

Indoor Air Quality (IAQ) is a significant health determinant in the building environment. Ventilation plays a significant role in providing comfortable working conditions and securing contaminant removal from indoor spaces. The heat and effluents generated by cooking activity need to be exhausted from the kitchen space to control the IAQ and provide thermal comfort. The study investigates the ventilation performance concerning IAQ of five institutional kitchens in an educational campus. This study evaluates the influence of building parameters on ventilation performance and IAQ using experimental research and Computational Fluid Dynamics (CFD). The empirical part includes field measurement of indoor airflow and IAQ indicators (particulate matter, CO2, temperature, and RH). The Integrated Environmental Solutions Virtual Environment (IESVE) software performs the CFD analysis. The 'Local Mean Age of air' (LMA) is used as a parameter to analyze IAQ. The findings reveal that the LMA reduces with increased cross-ventilation at the operational level and the presence of local exhaust ventilation, such as chimneys. Moreover, a higher slenderness ratio, lower aspect ratio, and lower building volume reduce the age of air.

Analysis of parameters for spray-local exhaust ventilation (SLEV) to minimize high-temperature smoke pollutants and reduce energy consumption

Industrial buildings often face limitations in placing local exhaust ventilation (LEV) near pollution sources, which can lead to ineffective control of high-temperature smoke. This study explores the integration of spray with local exhaust ventilation (SLEV) as a solution for smoke control and energy savings. The research identified a design law for spray parameters and developed a formula to calculate SLEV ventilation flow rate that considers the impact of spray. Results indicate that the spray field overlapping coefficient plays a key role in characterizing the position and spacing of multi-nozzles. As the spray field overlapping coefficient increases, the spray dust reduction performance indicator linearly increases, while the capture efficiency follows a pattern that aligns with the Boltzmann curve model. The optimal range for the spray field overlapping coefficient to achieve high efficiency in SLEV is between 0.45 and 0.55. The formula for ventilation flow rate calculation is applicable to common conditions with smoke velocities ranging from 4 to 12 m/s (Ar: 0.0149–0.1339). SLEVs demonstrate a 35.22 % improvement in dust removal efficiency and over 20 % energy savings compared to LEVs, contributing to the development of high-efficiency, energy-saving systems for sustainable industrial production.

Research on aerosol particles formed by laser interaction with various metals

Laser technologies are widely used in modern industry for cutting, welding, surface cleaning, drilling, and more, including in the nuclear industry for processing radioactively contaminated structures. These processes often lead to the formation of aerosol particles, including toxic nanoparticles, primarily oxides, which can penetrate cellular membranes and accumulate in the body. Understanding these particle formation processes is crucial for improving gas purification systems and personal protective equipment. This study utilized a ytterbium fiber pulsed-periodic laser (1.064 µm wavelength, 20 W power, 40 kHz pulse repetition rate, 200 ns pulse duration) to process various metals: aluminum (Al), bismuth (Bi), E110 alloy (Zr-based), carbon steel (St3), and stainless steel (08X18H10T). Aerosols were analyzed using a silicon monocrystalline substrate placed near the laser impact site, cleaned thoroughly to remove any contaminants. A 3D-printed model held the substrate at a 15-degree angle in the laser processing zone. Experiments were conducted in a closed box with local exhaust, positioning the substrate to capture the finest aerosol particles. Samples were analyzed using scanning electron microscopy (SEM) on a JEOL JSM-6480LV microscope. Results showed that aerosols formed consist of submicron agglomerates of particles smaller than 100 nm, with uneven deposition indicating air-borne agglomeration. Repeated scanning formed branched structures of interconnected nanoparticle agglomerates. In conclusion, laser processing with a 1.064 µm ytterbium fiber laser produces submicron aerosols of nanoparticles, presumably oxides. The deposition pattern suggests air-borne agglomeration, independent of the target material. These findings underscore the need for enhanced air purification and protective equipment to mitigate nanoparticle accumulation risks in respiratory organs and on skin during laser equipment operation.

Semi-quantitative health risk assessment of heavy metal dust exposure among nail technicians using the SQRA technique and Monte Carlo simulation.

Nail technology, including the application of artificial nails and nail care, is a developing sector of the global beauty industry. Nail technicians are exposed to a variety of chemical substances through inhalation, as they spend extended periods of time in close proximity to these materials. This study aimed to evaluate the semi-quantitative health risk of dust-containing heavy metals among nail technicians. This analytical descriptive study employed the risk assessment method provided by the Singapore Occupational Health Department to evaluate the health hazards of lead, cadmium, nickel, chromium, and manganese. Dust samples from nail filing were collected from the respiratory zone of 20 nail technicians following the NIOSH 7300 method. The samples were analyzed using ICP-OES instrumentation. Monte Carlo simulation was utilized to characterize the risk and its uncertainties. Manganese and cadmium had the highest and lowest mean concentrations, respectively. The risk scores of the metals ranked from highest to lowest were as follows: . All five metals had risk rankings below 2.8, signifying a minimal risk level. Sensitivity analysis using Spearman's correlation coefficient demonstrated a positive relationship between concentration, daily hours of exposure, and the number of workdays per week with the risk score (RR) and exposure level (ER). Conversely, the variable of weekly working hours (W) showed a negative correlation with these parameters. Despite the low-risk level of the examined metals, continuous exposure and potential long-term effects on nail technicians warrant preventive measures. Recommendations include implementing local exhaust ventilation systems, using table fans, establishing work-rest cycles, wearing N95 dust masks, and using reputable and high-quality nail polishes.

Airborne Benzene Concentrations Increase Trans, Trans-Muconic Acid (tt-MA) Levels and Liver Function in Workers in The Manufacturing Industry

The use of benzene as a solvent in the manufacturing industry can be dangerous because it is volatile, toxic, and carcinogenic. Exposure to benzene occurs through inhalation of the chemical in the air, which can enter the human body through the respiratory system. The levels of trans, trans-Muconic Acid (tt-MA), which is used to metabolize benzene, can be affected by the amount of exposure to the chemical. This study aims to determine the differences in exposure to benzene in the air by measuring the tt-MA indicators and liver function of workers in the manufacturing industry. This research uses an observational and cross-sectional approach, with a population of 158 employees from both administration and production units. The sample size for the study is 16 respondents, selected using the consecutive sampling technique. The research instrument uses a questionnaire and examines urine samples using the in-house method. Blood samples are examined using IFCC 37 C. The data is processed using the independent-sample t-test and Pearson correlation. The results show that the level of benzene in the air is below the threshold of 0.5 ppm. However, there is a significant difference in the results of tt-MA and SGOT (p<0.05), while the levels of SGPT (p>0.05) show no significant differences. In conclusion, there are differences in the tt-MA and SGOT exposure levels between workers in the production and toxicity units, while SGPT does not show significant differences. It is recommended that the industry maximizes the use of local exhaust ventilation and prohibits smoking.

Health and Safety Executive research on wood dust exposure controls in British manufacturing.

To generate new intelligence on occupational exposure to wood dust in woodworking manufacturing activities in Britain, the Health and Safety Executive (HSE) performed 22 occupational hygiene site visits to assess exposure and exposure controls between 2014 and 2017. The work aimed to characterise good practice and therefore sites with a poor health and safety record, as identified from HSE inspection records, were not invited to participate. Sites selected covered furniture production, joinery, saw milling, and boat building and repair. Twenty-three follow-up telephone interviews were also carried out across 15 of the companies with supervisors and managers to explore how they tried to promote good practice among the workforce, and if there are any potential challenges encountered. The aim of the interviews was to gain a better understanding of how to enable organisations to improve the management of wood dust exposure. This study found that 6.0% of all wood dust exposure measurements (15 out of 252) were above 5 mg/m³, and 17.6% of exposures to hardwood dust or mixtures of hardwood and softwood dust (38 out of 216) were above 3 mg/m³ (the then current and future workplace exposure limits). Sanding, cleaning, and maintenance activities were of particular concern. Improvements to exposure controls are required, in particular, improvements to local exhaust ventilation controls for hand-held power tools and hand sanding. The management, selection, and use of respiratory protective equipment were poor. All the managers and supervisors recognised that exposure to wood dust can pose serious health risks, and that controls were crucial to protecting workers' health. The findings from the telephone interviews suggest that supervision and provision of information about the health effects of exposure to wood dust were common approaches that organisations used to raise awareness and promote good practice, in relation to managing wood dust exposure. Worker attitudes towards controls, such as perceptions that they hinder task completion and habitual ways of working, were identified as factors influencing the use of controls. Risk communication approaches that focus on increasing workers' awareness of their susceptibility to ill-health using credible sources, such as peers, can help enhance the uptake of messages on the use of controls. Financial constraints were identified as a challenge to improving the control of wood dust, particularly for small companies.

On fatigue crack origin with a fine granular area in matrix without defect

Fatigue crack initiation in metallic materials during very high cycle fatigue has been characterized by a subsurface crack origin with defect such as an inclusion. In this paper, fatigue damage behavior in an austenitic stainless steel has been studied using a novel progressive stepwise load increasing test method with each cycle step higher than 108 cycles. Subsurface crack origin with a fine granular area has formed in the matrix without defect. This is a new phenomenon. The mechanism has been investigated using Focused Ion Beam cross-sectioning and electron channeling contrast imaging techniques. Strain localization, grain fragmentation and local plasticity exhaustion are the main factors that cause fatigue damage and crack initiation in the matrix. This study provides a fundamental understanding how material damage and crack initiation occur in material matrix during very high cycle fatigue.

Performance of low-volume air cleaner and local exhaust in mitigating airborne transmission in hospital outpatient rooms

This study intends to explore the effective and flexible solutions to cope with airborne transmission in hospital outpatient rooms. Such solutions might be used as an additional measure during pandemics and as an independent measure in regions with incomplete health facilities and limited resources. It first investigates the dispersion characteristics of exhaled pollutants during typical expiratory activities and then evaluates the effectiveness of a low-volume air cleaner and local exhaust in reducing the risk of cross infection using a newly proposed index, i.e., personal exposure reduction effectiveness (PERE). The results show that, though wearing a face mask largely obstructs the horizontal dispersion of exhaled particles and thus avoids short-range direct transmission, the influence of particles leaked from the edges of a face mask on the doctor and the next patient cannot be ignored. Under the conditions without wearing a face mask, a background ventilation rate of 60 m3/h plus a 50 m3/h desk-mounted air cleaner is effective to prevent the direct exposure of the doctor from the patient's exhaled particles, with the PERE reaching 90.1%. Under the conditions with wearing a mask, a background ventilation rate of 60 m3/h plus a 30–50 m3/h local exhaust above the patient's head removes 85.7%–88.5% of leaked particles, achieving a PERE of 96.6%–100%. The aforementioned PERE value during the two types of conditions is 137% (or 70.4%–71.4%) higher than that under only a background ventilation of the stipulated 120 m3/h by standard. These findings should provide ideas and information for improving the mitigating system of airborne transmission in hospital outpatient rooms.

Effectiveness of Cadaver Tables with Local Exhaust Ventilation in Reducing Formaldehyde Levels

Formaldehyde, which is exposure in the workplace, is very dangerous for health, especially for students, staff and lecturers in the anatomy laboratory room. Cadaver tables with local exhaust ventilation (LEV) in previous studies were used to reduce formaldehyde levels in the anatomy room. This study aimed to determine the effectiveness of a cadaver table with local exhaust ventilation to reduce formaldehyde exposure. Using a pre-post study, this study showed that a cadaver table with local exhaust ventilation can reduce formaldehyde exposure significantly (p<0.001) with a confidence interval of 2.715–2.186. The percentage reduction in formaldehyde levels at each measurement point was 31% - 89% (min-max). This showed that the cadaver table with LEV was effective in reducing formaldehyde levels.