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Purpose: This research focuses on the development and characterization of oil-wetted spun-bonded polypropylene (PP) non-woven filters for improved air intake systems in automobiles. The study aims to enhance engine performance, durability, fuel economy and emission reduction by addressing key aspects such as contaminants filtration efficiency, loading capacity, pressure drop, temperature performance and longevity. Design/methodology/approach: The research methodology involves the utilization of textile fabrics, particularly oil-wetted spun-bonded PP non-woven filters, renowned for their effective particle collection capability from intake air. Experiments were conducted using a Box–Behnken design with three variables – oil concentration, areal density and dust quantity – each at three different levels to establish correlations with the filter's dust holding capacity (DHC) and pressure drop. Findings: The findings indicate that immersing particles in oil-coated medium significantly enhances the filter's DHC. Notably, castor oil as a coating demonstrates remarkable results, with a 97.53% increase in DHC and a high particulate matter filtration efficiency of 94.12%. Originality/value: This study contributes to the originality of research by emphasizing the importance of oil density in determining the filter's DHC and filtration efficiency. Furthermore, it highlights the superiority of castor oil over coconut oil-coated filter media, advancing air intake and/or filter systems for automotive engines. [ABSTRACT FROM AUTHOR]

Non-medical masks such as disposable non-medical, commercially produced cloth, and homemade masks are not regulated like surgical masks. Their performance, in terms of filtration efficiency and breathability, is variable and unreliable. This research provides a quantitative evaluation of various non-medical masks, assesses their fabrics' potential for the reduction of transmission of bioaerosols such as the SARS-CoV-2 virus, and compares them to surgical masks and N95 filtering facepiece respirators. Using a testing line with a NaCl challenge aerosol, four types of commercial reusable cloth masks, two types of disposable non-medical masks, three types of surgical or N95 masks, and seven types of commonly available materials were tested individually and in combinations. The testing line and procedure were adapted from the ASTM F2299-03: Standard Test Method for Determining the Initial Efficiency of Materials Used in Medical Face Masks to Penetration by Particulates Using Latex Spheres testing method used for testing surgical masks. Filtration efficiencies at 0.15 µm particle diameter at a face velocity of 25 cm/sec for commercial cloth masks, disposable non-medical masks, surgical masks, commercial mask combinations, and homemade combinations ranged from 16–29%, 39–76%, 91–97%, 51–95%, and 45–94%, respectively. The pressure drop results for the different masks and material combinations were all under 3 mm H2O/cm2 except for one material configuration. This study builds on other research that looks at individual materials and masks by testing combinations alongside the individual masks and materials. With proper layering, household materials can achieve the filtration efficiency and low pressure drop requirements of surgical masks. The filtration capabilities of disposable and cloth mask fabrics vary considerably meaning that they are not a reliable or consistent facemask option, regardless of fit. [ABSTRACT FROM AUTHOR]

Abstract Non-contact methods are useful to improve the quality control of particle filtration media. The purpose of this paper is to investigate the correlation between the filtration efficiency of a porous sheet and its ultrasonic properties obtained using a non-contact technique. An air-coupled ultrasonic technique is used to obtain rapid measurements without affecting the integrity of the material. High frequencies (from 0.1 to 2.5 MHz) are used to improve technique sensitivity, and transmitted waves are measured to probe the internal properties of the material. Measurements of transmission coefficient spectra (amplitude and phase) and the corresponding ultrasound velocity and attenuation coefficient at different frequencies are obtained for a set of filtration media with well-characterized properties. Results show that the ultrasonic properties of filtration media vary as a function of basis weight, and therefore filtration efficiency, for a given charge state. However, the effect of electrostatic charge on ultrasonic propagation is almost negligible, as expected. We conclude that ultrasonic transmission may provide a valuable tool for the continuous online monitoring of material quality during fabrication and as a method to tease apart mechanical and electrostatic contributions to particle filtration.

The commercial application of engineered nanoparticles (ENPs) has rapidly increased as their unique properties are useful to improve many products. ENPs, however, can pose a major health risk to workers through exposure routes such as inhalation and dermal contact. Research is lacking on the protective nature of lab coats when challenged with ENPs. This study investigated multiwalled carbon nanotubes (CNTs), carbon black (CB), and nano aluminum oxide (Al2O3) penetration through four types of lab coat fabrics (cotton, polypropylene, polyester cotton, and Tyvek). Penetration efficiency was determined with direct reading instruments. The front and back of contaminated fabric swatches were further assessed with microscopy analysis to determine fabric structure with contaminated and penetrated particle morphology and level of fabric contamination. Fabric thickness, porosity, structure, surface chemistry, and ENP characteristics such as shape, morphology, and hydrophobicity were assessed to determine the mechanisms behind particle capture on the four common fabrics. CNTs penetrated all fabrics significantly less than the other ENPs. CNT average penetration across all fabrics was 1.83% compared to 15.74 and 11.65% for CB and Al2O3, respectively. This can be attributed to their fiber shape and larger agglomerates than those of other ENPs. Tyvek fabric was found to be the most protective against CB and Al2O3 penetration, with an average penetration of 0.06 and 0.11%, respectively, while polypropylene was the least protective with an average penetration of 40.36 and 15.77%, respectively. Tyvek was the most nonporous fabric with a porosity of 0.50, as well as the most hydrophobic fabric, explaining the low penetration across all three ENPs. Polypropylene is the most porous fabric with a porosity of 0.77, making it the least protective against ENPs. We conclude that porosity, fabric structure, and thickness are more important fabric characteristics to consider when discussing particle penetration through protective clothing fabrics than surface chemistry. [ABSTRACT FROM AUTHOR]

Physical and chemical properties of aerosol, filter media properties, aerosol composition, dust cake properties, construction of filter unit, dew point and temperature are the parameters that affect the filtration performance during the control of industrial air pollution. No comprehensive experimental study has been reported on the effect of varying cleaning cycle times on the filtration performances, and no emission study at the clean side was conducted using PTFE-coated membrane on polyester needle punched filter media. In this experimental work, we are studying the filtration performances and characterization of emitted particles with varying cleaning cycle times in a pulse jet filtration system with membrane-coated media. The particulate emissions in terms of PM2.5 and PM10 are substantially lower, when using a coated membrane on filter media. Mass concentration and number concentration in downstream emission is also lower for filter media using PTFE membrane on needle felt nonwovens fabric media. Filtration efficiency is higher for filter media with PTFE coated than without PTFE membrane coating. PTFE membrane-coated media fabric exhibits lower residual pressure drop (∆P), which ultimately enhances the filter media life, more energy saving and better control on emissions. The downstream D10, D50, and D90 particles values are much higher in non-PTFE membrane-coated filter media. Overall, it is observed that fabric filter media with PTFE membrane, arrests a higher proportion of the fine particles, which causes lesser impacts on human health by industrial air pollution. Hence, the membrane-coated filter media (i.e. membrane separation) effectively controls the fine particles emission at downstream side/clean side. [ABSTRACT FROM AUTHOR]

Non-contact methods are useful to improve the quality control of particle filtration media. The purpose of this paper is to investigate the correlation between the filtration efficiency of a porous sheet and its ultrasonic properties obtained using a non-contact technique. An air-coupled ultrasonic technique is used to obtain rapid measurements without affecting the integrity of the material. High frequencies (from 0.1 to 2.5 MHz) are used to improve technique sensitivity, and transmitted waves are measured to probe the internal properties of the material. Measurements of transmission coefficient spectra (amplitude and phase) and the corresponding ultrasound velocity and attenuation coefficient at different frequencies are obtained for a set of filtration media with well-characterized properties. Results show that the ultrasonic properties of filtration media vary as a function of basis weight, and therefore filtration efficiency, for a given charge state. However, the effect of electrostatic charge on ultrasonic propagation is almost negligible, as expected. We conclude that ultrasonic transmission may provide a valuable tool for the continuous online monitoring of material quality during fabrication and as a method to tease apart mechanical and electrostatic contributions to particle filtration. [ABSTRACT FROM AUTHOR]

To investigate the hydraulic effects and performance of the micro-pressure filtration and cleaning tank under conditions with sandy and brackish water, physical model tests were conducted with five groups of flow rates (6–14 m³ h−1), four groups of sediment contents (0.5–2.0 g l−1), five groups of mineralisation degrees (0–5.0 g l−1), and three groups of screen apertures (0.125, 0.150, and 0.180 mm). Dimensional analysis, multiple linear regression analysis, and the non-dominated sorting genetic algorithm II (NSGA-II) were used to analyse the test results. The results showed that the optimal operating conditions of the micro-pressure filtration and cleaning tank under the scope of this test were a screen aperture of 0.175 mm, a flow rate of 13 m3 h−1, a sediment content of 1.8 g l−1, and a mineralisation degree of 4.7 g l−1. The micro-pressure filtration and cleaning tank was intermittently discharged and rinsed, the discharge time was 30–40 s, and the flow rate of discharge and rinsing was 5.54 m3 h−1. Prediction models of the head loss and the filtration efficiency of the filter were established. The coefficients of determination (R2) were greater than 0.9, the average relative errors of the predicted and measured values were 2.98% and 2.17%, respectively, and the corresponding root mean square errors were 0.0549 m and 0.642. The research results can be used as a reference for in-depth investigations on the performance of the micro-pressure filtration equipment in front of pumps. • Head loss and filtration efficiency models of pre-pump filters were established. • Optimal working condition of the filter was obtained using NSGA-II. • Optimal discharge time and discharge flow rate were determined. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

AbstractThis study enhances the understanding of virus removal efficiency by filters, crucial for predicting respiratory disease transmission risk and guiding outbreak prevention. Current research often neglects the survival behaviour of pathogens. Addressing this, our research develops a novel approach anchored in medical experimental data. A mathematical model was established to depict the dynamic changes in particulate concentration within non-centralized air-conditioned rooms, considering indoor and outdoor concentrations, natural ventilation, and filter dynamics. The model’s reliability was affirmed through particle and aerosolized pathogen filtration experiments, showing an R2 value over 0.99, indicating strong agreement with empirical data. Analysis of filter operation, both with and without infection sources during epidemics, reveals that the use of split air conditioners and filters significantly reduces pathogen concentration. Pathogens trapped in filters undergo natural decay, considerably lowering transmission risk compared to airborne states. This research offers a scientifically grounded, precise methodology for evaluating respiratory disease transmission risks, contributing substantially to public health management.

Abstract Objectives Due to the COVID-19 pandemic and the shortage of the National Institute for Occupational Safety & Health (NIOSH)-approved N95 respirators, the Food and Drug Administration granted an Emergency Use Authorization to allow the use of non-NIOSH approved respirators provided that these respirators must undergo tests by a protocol of TEB-APR-STP-0059, similar methods of NIOSH standard testing procedure. This initiative safeguards the quality of respirators and the effectiveness of occupational protection. The dataset of all the testing results could benefit further analysis of COVID-19 infection rates in relation to different types of N95 respirators used and identify potential correlations of various test parameters in the testing system for validation. The analysis enhances understanding of the quality, effectiveness, and performance of N95 respirators in the prevention of respiratory infectious transmission and develops improved occupational safety measures. Data description The dataset was transformed, transcribed, and compiled from the official testing data of non-NIOSH-approved N95 respirators reported in the NIOSH website under the Centers for the Disease Control and Prevention in the United States. The dataset included details of 7,413 testing results of N95 respirators (manufacturer, model, and maximum and minimum filtration efficiency) and test parameters (flow rate, initial filter resistance, and initial percent leakage). Supplementary items were added to increase the availability of data analysis and enhance the interpretability of the assessments of the quality of N95 respirators.

Considering the high demand for air quality, the development of biomass-based air filtration membranes with high air filtration efficiency and good stability is an urgent task. In this work, polyvinyl alcohol (PVA), gelatin (GA), and cellulose nanocrystals (CNC) were mixed and prepared into a membrane through an electrospinning method for air filtration. After a hydrophobic modification, the modified PVA/GA/CNC composite membrane showed excellent filtration efficiency for PM2.5 (97.65%) through the internal three-dimensional structure barrier and the electrostatic capture effect of the CNC with a negative charge, as well as a low-pressure drop (only 50 Pa). In addition, the modified PVA/GA/CNC composite membrane had good mechanical properties (maximum tensile fracture rate of 78.3%) and high stability (air filtration efficiency of above 90% after five wash-filter cycles and a high-temperature treatment at 200 °C). It is worth noting that the whole preparation process is completed without organic solvents, putting forward a new strategy for the construction of green air filtration membranes. [ABSTRACT FROM AUTHOR]

Objectives: Due to the COVID-19 pandemic and the shortage of the National Institute for Occupational Safety & Health (NIOSH)-approved N95 respirators, the Food and Drug Administration granted an Emergency Use Authorization to allow the use of non-NIOSH approved respirators provided that these respirators must undergo tests by a protocol of TEB-APR-STP-0059, similar methods of NIOSH standard testing procedure. This initiative safeguards the quality of respirators and the effectiveness of occupational protection. The dataset of all the testing results could benefit further analysis of COVID-19 infection rates in relation to different types of N95 respirators used and identify potential correlations of various test parameters in the testing system for validation. The analysis enhances understanding of the quality, effectiveness, and performance of N95 respirators in the prevention of respiratory infectious transmission and develops improved occupational safety measures. Data description: The dataset was transformed, transcribed, and compiled from the official testing data of non-NIOSH-approved N95 respirators reported in the NIOSH website under the Centers for the Disease Control and Prevention in the United States. The dataset included details of 7,413 testing results of N95 respirators (manufacturer, model, and maximum and minimum filtration efficiency) and test parameters (flow rate, initial filter resistance, and initial percent leakage). Supplementary items were added to increase the availability of data analysis and enhance the interpretability of the assessments of the quality of N95 respirators. [ABSTRACT FROM AUTHOR]

Some users consider modern hydrostatic drives and controls to be unreliable and difficult to maintain. This view is often due to operational problems caused by issues with obtaining and then maintaining the appropriate cleanliness class of the working fluid. Recommendations on the selection of appropriate filtration system elements can be found in the literature, but there is no numerical model that could be helpful in a detailed analysis of the phenomenon. In the article, the authors tried to fill the research gap regarding the lack of a filtration model based on the filtration efficiency coefficient of filter elements used in hydraulic drives and controls. The developed model allows users to determine the influence of selected filtration system parameters on the separation of contaminants by filter elements. The model is intended to help designers and users of hydraulic drives and controls in optimizing the filtration system in order to obtain and then maintain the required cleanliness class of the hydraulic fluid. This paper also includes the results of the sensitivity analysis of selected filtration-system operating parameters in terms of the highest efficiency. In order to verify the developed model, experimental tests were also carried out, with the results presented in this paper. Based on the numerical analyses and experimental studies, recommendations that may be helpful in the selection or development of filtration systems used in hydrostatic drives and controls were developed. [ABSTRACT FROM AUTHOR]

Protection from nuclear biochemical aerosol and air pollution pays attention to aerosol mass concentration. The concentration of upstream aerosol of the commonly used filtration efficiency detection device for high-efficiency filter materials is low, making it insufficient for detecting the filtration efficiency of high-efficiency filter materials. This study designed and built a set of filtration efficiency detection devices for high-efficiency filter materials based on mass concentration. By adjusting the oil bath temperature, injection pressure, the degree of spiral-separator separation, as well as the number and size of nozzles, we investigated the effects of each condition on the concentration and particle size distribution of aerosol generation. As a result, the oil mist generator of the device can stably generate high-concentration aerosol with a mass concentration of up to 1587.9 mg/m3 and a number concentration of up to 107–108 P/cm3. The high-concentration aerosol generated can meet the E11–U15 filter material performance requirements. [ABSTRACT FROM AUTHOR]

New substances and particles appearing in the environment following technological development pose new challenges for separation methods. Moreover, the growing amount of waste also forces us to look for environmentally friendly solutions. One way to create filtration structures with the desired properties is to combine known techniques, thanks to which the advantages of one technique complement the deficiencies and disadvantages of another. Combining the melt-blowing and solution-blowing processes seems to be promising. Fibres created from melt-blowing will provide mechanical strength, while solution-blowing will allow the introduction of nanofibres into the structure with unique filtration and functional properties. Both methods enable working with biodegradable polymers, so the resulting filter can also be environmentally friendly after operation. Our research aimed to check whether combining two fibre production techniques (melt-blown and solution-blowing) is possible and how the joining method will affect the final product. We created a multilayer structure by placing a layer of solution-blowing nanofibres between melt-blown layers, and a mixed structure by simultaneous melt-blowing and solution-blowing. The created multilayer structure was characterised by high filtration efficiency and high-pressure drop. In contrast, the mixed structure achieved a high-quality factor and high mass of deposited droplets per 1 J of energy used for work. [ABSTRACT FROM AUTHOR]

In order to increase the product diversity and wide application of cellulose acetate fiber in the field of nonwoven filtration, combined with the rapid development of green fiber, the response surface methodology (RSM) was used to optimize the parameters of cellulose acetate/polylactic acid (CA/PLA) nonwoven in the preparation process. The hybrid ratio, linear density, and fiber length of CA fiber were selected to optimize the preparation process of nonwovens with filtration efficiency and tensile strength as response values. The results showed that the hybrid ratio was 80%, the linear density was 3.33dtex, and the fiber length was 46 mm. Under this process, the filtration efficiency of CA/PLA nonwoven is 35.74%, longitudinal tensile strength is 0.734 MPa, and transverse tensile strength is 1.782 MPa, which is close to the theoretical value, indicating that RSM has application value. It can provide a theoretical basis for the preparation parameters of nonwovens with excellent tensile strength and filtration efficiency at the same time. In addition, the air permeability, filtration resistance, and surface morphology of CA/PLA nonwovens were tested. It was found that the effect of hybrid ratio on air permeability and filtration resistance is not obvious, but linear density and fiber length are significant, and CA/PLA nonwovens are three-dimensional structures with disorderly surfaces, which are conducive to filtering dust, particles, and other impurities in the air. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Fiber Inspection / Zhongguo Xian-Jian is the property of China Fiber Inspection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the filtration efficiency by using the fine diameter and hot piezoelectric properties of PVDF fiber membrane, the PVDF fiber membrane was prepared using electrospinning. SEM and XRD were employed to characterize the morphology and β crystal phase transformation of PVDF fiber membrane. The PVDF fiber membrane was attached to PPS filter material to prepare PPS/PVDF composite filter material, and its filtration efficiency and differential pressure characteristics were evaluated. The results show that the PVDF fiber membrane has no beaded structure, the fiber diameter distribution ranges from 270 to 780 nm, with a median value of 427. 3 nm, and the crystal structure is mainly β crystal phase. With the increase of wind speed, the filtration efficiency of PPS/PVDF fiber membrane composite filter material exhibited a lesser decrease, which proves that the piezoelectric effect of PVDF fiber membrane improves the filtration efficiency of fine particles. As the temperature increases, the PVDF fiber membrane exhibits thermoelectricity, and the filtration efficiency of the composite filter material increases. When the temperature rises to 70 ℃, the filtration efficiency of the particles with a small size 0. 3 µm can be maximally increased by 28. 37%. [ABSTRACT FROM AUTHOR]

Background The effectiveness of cloth face masks to prevent viral spread has not yet been conclusively established. In this meta-analysis, we evaluate their effectiveness in comparison to standard medical/surgical and N95-typed masks against viral spread. Methods We identified literature through a systematic search in three databases and meta-analytically synthesized relevant studies by means of random-effects as well as multilevel modelling. Results Twelve studies comprising k  = 28 effect sizes (N  = 338) were included. Medical/surgical and N95-typed masks outperformed cloth masks, yielding a large effect (g  = 1.40). This effect remained robust when data were grouped according to comparisons with medical/surgical masks (g  = 1.25) and N95-typed masks (g  = 1.29). However, effects were differentiated according to mask fit, indicating reversals of signs when cloth mask effects were compared with ill-fitting medical/surgical and N95-typed masks (g s = −12.50 and − 10.90, respectively). Conclusions Cloth face masks were found to have significantly poorer filtering performance than medical/surgical masks and N95 masks, but only if non-cloth masks were properly fitted. Our results illustrate the necessity of using well-fitting medical/surgical or N95-typed masks to prevent viral spread, although some allowance should be made in circumstances where higher compliance with cloth mask mandates are expected. [ABSTRACT FROM AUTHOR]

Normally, atmospheric air plasma is usually utilized to hydrophilize the substrate surface. In this paper, a facile and fast method is reported to prepare hierarchical superhydrophobic surface via atmospheric air dielectric barrier discharge (DBD) with sealed discharge zone. Siloxane monomers along with silica nanoparticles were used to construct micro-scale hierarchical morphology in gas phase. It is verified that the water repellency of sample could be regulated through adjusting volume and air humidity of discharge zone. The generated reactive oxygen species induced polymerization of long-chain alkyl silane and also caused the grafting of polar groups on substrate surface. Within 5 min, the long-chain alkyl silane coating could rapidly wrap silica nanoparticles layer-by-layer to form microspheres and hence the micro-scale hierarchical morphology. The discharge zone with appropriate sealing volume could balance the grafting amount of polar and nonpolar groups to optimize surface hydrophobicity. After repeating the plasma treatment three times, the sample possessed superhydrophobicity and excellent performance in water-in-oil emulsion separation. The study may offer an environment-friendly method to prepare water-repellent materials for industrial applications. [ABSTRACT FROM AUTHOR]

Microplastics is an emerging pollutant that pollutes water and great threat to the environment. To remove microplastics and other pollutants from drinking water, a biodegradable multifunctional filter was developed from a natural resource (coir fibre and pith) to reduce microplastic pollution in the environment. Coir fibre and pith were alkali-treated with 5% sodium hydroxide to expose the surface morphology (pores and cellulose) and functionalized with chitosan using citric acid as a cross-linker. As per the experimental plan developed by the Box–Behnken method, chitosan (1%, 2% and 3%) was cross-linked with coir fibre and pith by citric acid (5%, 10% and 15%) at various curing temperatures (120 °C, 130 °C and 140 °C). Characterization by Fourier transform infrared spectroscopy and thermogravimetric analysis was performed to analyse the cross-linking nature. Regression and composite desirability analysis was conducted to find the best input parameters which are 1% chitosan, 10% citric acid concentration and 120 °C curing temperature. The filter was constructed from the functionalized fibre and pith with the parameters of variation in fibre and pith weight and fibre length and evaluated for removal of microplastics, heavy metal ions (Pb, Cd and Cr) and total organic content. Filtration efficiency was analysed by the Box-Behnken method, and based on composite desirability analysis, 5 g of fibre, 3 g of pith and 1 cm fibre length are the best parameter to achieve maximum efficiency. The removal efficiency of the filter for microplastics was 99%, total organic content 94% and heavy metal ions in the order of Pb(II) > Cr(VI) > Cd(II). [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a new type of emerging pollutant in the aquatic environment that pose a tremendous risk to aquatic organisms and human health. Although many studies have focused on the removal of MPs, most of the materials used are non-renewable, non-degradable, and relatively costly. The development of green, renewable, and cost-effective materials for the removal of MPs presents a significant challenge. In this work, cellulose nanofiber-coated, delignified wood (CNF-CDW) was prepared and used as an efficient filter to remove MPs for the first time. Balsa wood chip was delignified through three approaches using NaClO 2 , Na 2 SO 3 /NaOH, and a deep eutectic solvent (DES) consisting of choline chloride/lactic acid. Delignified wood (DW) with desirable mechanical properties and a high pore structure was successfully prepared by optimizing the delignification method and reaction conditions. Subsequently, the CNF-CDW was prepared through immersion of DW in a suspension of cellulose nanofiber (CNF), followed by crosslinking with CaCl 2 solutions. The effects of CNF concentration, CaCl 2 concentration, and wood chip thickness on the removal efficiency and flux of CNF-CDW towards polystyrene (PS) MPs were systematically studied. Under the optimal conditions of 0.5 ​wt% CNF, 1 ​mol/L CaCl 2 , and 10 ​mm in thickness, the CNF-CDW exhibited superior MPs removal performance, with a removal efficiency of 95.97% and a flux of 1146 ​L/m2·h. Morphological analysis revealed that CNF formed compact films on the surface DW, and MPs were efficiently blocked both on the surface and internal cellular structure of CNF-CDW. Therefore, with its exceptional filtration efficiency, high flux, and sustainable nature, CNF-CDW has a broad application prospect in the field of removing MPs from aquatic environment, promoting a brighter and cleaner future for aquatic ecosystems and human well-being. [Display omitted] • An eco-friendly DES was used to mildly remove lignin and hemicellulose from wood. • Delignified wood (DW) exhibited a high pore structure and large specific surface area. • Cellulose nanofibers (CNFs) were further coated onto DW via crosslinking strategy. • CNF-coated DW displayed excellent performance in the removal of microplastics. [ABSTRACT FROM AUTHOR]

The emergence of facial masks as a critical health intervention to prevent the spread of airborne disease and protect from occupational nanomaterial exposure highlights the need for fundamental insights into the interaction of nanoparticles (<200 nm) with modern polymeric mask filter materials. While most research focuses on the filtration efficiency of airborne particles by facial masks based on pore sizes, pressure drop, or humidity, only a few studies focus on the importance of aerosol surface charge versus filter surface charge and their role in the net particle filtration efficiency of mask filters. In this study, experiments were conducted to assess mask filter filtration efficiency using positively and negatively charged polystyrene particles (150 nm) as challenge aerosols at varying humidity levels. Commercial masks with surface potential (Ψf) in the range of −10 V to −800 V were measured by an electrostatic voltmeter and used for testing. Results show that the mask filtration efficiency is highly dependent on the mask surface potential as well as the charge on the challenge aerosol, ranging from 60% to 98%. Eliminating the surface charge results in a maximum 43% decrease in filtration efficiency, emphasizing the importance of electrostatic charge interactions during the particle capture process. Moreover, increased humidity can decrease the surface charge on filters, thereby decreasing the mask filtration efficiency. The knowledge gained from this study provides insight into the critical role of electrostatic attraction in nanoparticle capture mechanisms and benefits future occupational and environmental health studies. [ABSTRACT FROM AUTHOR]

The microfluidic inertial impactor can be used as the first-stage filtration device in the filtered containment venting system (FCVS). This equipment can separate radioactive aerosols from the flowing medium passively, enabling rapid depressurization of the containment and initial filtration of radioactive aerosols after severe accidents. Thereby, the safety and stability of FCVS operation can be improved by reducing the total amount of aerosol filtration in subsequent equipment. In order to investigate the filtration behavior of aerosols in the inertial impactor, a visualization experimental device with a transparent observation window was designed. This device was utilized to conduct visualization experiments that focused on studying the deposition distribution of aerosols within the inertial impactor. Furthermore, tests were performed to evaluate the inertial impactor’s aerosol filtration efficiency and dust holding capacity. The experiment utilized the isokinetic sampling method and membrane weighing method to measure the aerosol concentrations upstream and downstream of the inertial impactor, both before and after filtration. Furthermore, to account for potential interference caused by aerosol interception and adsorption by the inner walls of the experimental section, the correlation ratio of the filtration system was also measured. Comparison of the experimental results with the corresponding numerical simulations reveals that the deposition distribution of aerosols observed in the visualization model accurately reflects the airflow patterns and the trajectories of the particles within the inertial impactor. Furthermore, the visualization experiments suggest that the majority of the aerosols are deposited on the upper surface of the filtration unit and the inner wall of the microchannel, demonstrating a filtration efficiency of over 60%. These findings validate the structural design of the microchannel inertial impactor and support its suitability for efficient aerosol collection. Based on the research findings regarding the cumulative effect on filtration efficiency over time, it is evident that continuous filtration leads to the gradual accumulation of aerosol particles on the surface of the filter unit of the inertial impactor. Simultaneously, there is a continuous increase in the number of particles adhering to the inner wall of the microchannel, which can result in changes in the surface characteristics of the impactor channels. Thus, it can be concluded that, under dust-holding conditions, the aerosol filtration efficiency of the inertial impactor will progressively improve as more aerosol particles are deposited. However, when the airflow velocity within the inertial impactor surpasses a critical value, the re-entrainment of high-speed gas flow onto the deposited particles causes a decrease in aerosol filtration efficiency due to particles re-suspension.

Air filtration is an urgent global need because, in many countries and regions, the high concentration of inhalable suspended particles in the air is causing irreversible damage to human health. The use of nanofibrous membranes can help to reduce airborne particulate matter because of their large surface area, extremely porous structure, and adjustable pore size. However, despite their unique properties, the main drawbacks of nanofibre membranes are their poor mechanical properties. This review focuses on nanofibrous membranes prepared by electrospinning, a versatile technique in which the process parameters allow control of the morphology and dimensional characteristics of the nanofibres. Recent literature on air filtration is reviewed, focusing on the performance of materials such as pure or mixed polymers, organic–inorganic composites, and ‘green’ materials in the form of nanofibrous membranes. Finally, the recently proposed layered structures for nanofibre-based air filters are reviewed, offering the latest and most innovative solutions.

Lubricating oil is easily polluted by solid particles, causing it to deteriorate; therefore, solid particles must be separated from the oil. Furthermore, as conventional filtration devices cannot meet both filtration accuracy and service life requirements, an oil and solid separation method for multi-gradient filtration enhanced by an electric field is proposed. A numerical model for multi-gradient separation was established by coupling the governing equations of electric and flow fields, the particle-wall collision equation, and the discrete phase-tracking equation. Enhanced by an electric field, the characteristics of the multi-gradient filtration of solid particles in oil were investigated using finite element method. The effects of the main control parameters on the filtration performance were analyzed. The results indicate that using the electric field-enhanced multi-gradient filtration method can achieve highly efficient separation of solid particles from the oil. When the electric field strength was increased from 0 kV/mm to 2 kV/mm, the deposition concentration of particles was 2.5 times higher and filtration efficiency of the system increased to 97.46%. Additionally, the deposition concentration and filtration efficiency decreased from 0.15 m/s to 0.3 m/s, while gradually increased from 0.3 m/s to 0.5 m/s, for a particle size range of 10–40 µm. [Display omitted] • An oil and solid separation method for multi-gradient filtration enhanced by an electric field was proposed. • A numerical model for multi-gradient separation enhanced by an electric field was established. • Characteristics of electric field-enhanced multi-gradient of solid particles in oil were investigated. • The effects of the main control parameters on the filter efficiency were analyzed. [ABSTRACT FROM AUTHOR]

Nanofibrous aerogels (NFAs) have great application potential in air filtration due to their unique hierarchical porous structure and high porosity. However, the development of air filter with high air filtration efficiency, as well as good antibacterial activity, remains a major challenge. In an effort to overcome this challenge, here we report a facile methodology for the fabrication of robust and flexible nanofibrous aerogel membranes (NFAMs) with a three‐dimensional (3D) hierarchical porous structure. Moreover, the microstructures and filtration performance of the obtained NFAMs could be easily tuned by adjusting the nanofiber concentration in the aerogel. The resultant Ag@PAN/PBA NFAMs had high filtration efficiency (99.82%) towards PM0.3, low pressure drop (134 Pa) and desirable quality factor (0.0472 Pa−1) under an airflow velocity of 32 L/min. Furthermore, the NFAMs also exhibited excellent antibacterial activities against Escherichia coli (99.46%) and Staphylococcus aureus (99.72%). Together, the results presented here suggest that Ag@PAN/PBA NFAMs have great potential in public health protection applications. [ABSTRACT FROM AUTHOR]

Fractal theory was used to characterize particles and particle trapping parameters to accurately predict the particle filtration process inside a gasoline engine particle filter (GPF). The particles were fractal aggregates, and the fractal dimension (Df) was introduced to redefine the particle size. The porous medium inside the particle filter was a solid phase fractal. The pore tortuosity fractal dimension (Dt) and the pore area fractal dimension (Da) were introduced to define the fiber length of the trap. The Brownian diffusion coefficient and permeability were modified. A new fractal numerical model of GPF filtration efficiency was proposed based on the classical filtration theory. The results show that the fractal expansion model of filtration efficiency has good applicability. The influence of GPF structural parameters on filtration efficiency and pressure drop was analyzed. In this study, two performance metrics, trapping efficiency and pressure drop, were considered by fractal expansion filtration modeling. It is possible to increase or decrease filtration efficiency by adjusting the porosity and pore diameter. [ABSTRACT FROM AUTHOR]

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Baghouse is effective for controlling the particles emitted from industrial production, and the in‐situ leakage detection of a single bag filter is essential for maintaining the high filtration performance of the whole baghouse. In the present study, the changes of PM emission concentration induced by the leakage of the bag filter materials was studied. The results showed that the concentration of particles in the size range of 20–1000 nm significantly increased when the bag filter sample had three holes with a diameter of ~500 μm. In order to prevent the loss induced by the leakage of bag filter, a resistance sensing method was developed to detect the early leakage of single bag filter. The effectiveness of proposed sensing method was verified by detecting the leakage of polymethyl methacrylate (PMMA) bag filter. A sensing grid made of PMMA conductive threads was embedded in the PMMA bag filter, and the resistance change (ΔR) induced by the broken of sensing grid was used as sensing signal. The ΔR of sensing grid was 3.24, 3.31, and 3.05 Ω, respectively, when the bag filter failed due to the mechanical stress, chemical corrosion, and thermal erosion. Moreover, a model was proposed to predict the numbers of broken conductive PMMA threads that could indicate the damage area of the failed bag filter. [ABSTRACT FROM AUTHOR]

This research explores the possibility of tuning the structure of needle-punched nonwoven fabrics by incorporating layers of differently oriented fibres. The fibre orientation in carded batts is regulated with the help of carding parameters viz. feeder, cylinder, and doffer speeds. The carding parameters were optimized by using response surface methodology to obtain carded batts of differently oriented fibers, which were then placed distinctly to form composite layered nonwoven fabrics. The physical, mechanical, and functional properties of layered fabrics were evaluated. X-ray computed tomography technique was used for comprehensive evaluation of the packing densities at incremental thickness of layered fabrics. The obtained trends of packing density were found to be in good agreement with the measured properties of nonwoven fabrics. The creation of an inverse gradient of packing density in a layered nonwoven fabrics displayed close to highest filtration efficiency and close to lowest pressure drop. [ABSTRACT FROM AUTHOR]

Efficient oil filtration is crucial for maintaining optimal engine performance and preventing damage, wear, and potential malfunctions in marine diesel engines. Contaminants present in fuel and lubricants can adversely affect combustion and engine operation. This article explores the significance of fuel and oil purification in marine diesel engines, focusing on techniques such as sedimentation, filtration, and centrifugation. The study highlights the substantial consumption of lubricants by marine diesel engines and their vulnerability to contamination. Increased lubricant consumption can result in wear and decreased efficiency. Thus, effective oil purification methods play a pivotal role in extending engine lifespan, reducing wear, and ensuring environmentally responsible operation. Three primary methods of oil purification are discussed: sedimentation, filtration, and centrifugation. Sedimentation allows particles to settle due to gravity, filtration employs filters to capture solid impurities, and centrifugation utilizes centrifugal force to separate impurities based on density differences. To assess filtration efficiency, a practical scenario is presented, comparing full-flow, partial-flow, and combined filters. The article emphasizes the need for real-world data to make informed decisions about oil filtration methods. Furthermore, it highlights the importance of mathematical models, such as the Darcy-Brinkman equation, for understanding fluid movement and contamination distribution. Effective oil purification is essential for marine diesel engines to ensure optimal performance, reduce wear, and minimize environmental impact. By employing efficient filtration methods and leveraging mathematical models, marine industries can enhance their maintenance practices and contribute to the longevity and sustainability of their engines. [ABSTRACT FROM AUTHOR]

The elevated use of petroleum-based polymers to manufacture single-use disposable face masks is a serious environmental concern that has detrimental effects on the ecosystem. The research on using biodegradable facemasks is promising to reduce the environmental impacts of the single-use nondegradable facemask. A reusable cloth-based facemask with effective filtration could benefit society. Many studies suggest polyvinyl alcohol (PVA), polybutylene adipate terephthalate (PBAT), and polylactic acid (PLA) as viable biopolymers for facemask filter layer fabrication. In this work, an electrospun filter layer inserts with PVA, PBAT, and PLA polymers were produced by depositing electrospun nanofibers on non-woven cotton layers followed by conventional sealing. The fabricated filter inserts were used in cloth-based facemasks and were tested for filtration efficiencies and breathability. PVA facemask insert showed the best performance with 66.7% filtration efficiency and breathability of 0.66 m bar, whereas the lowest filtration efficiency was found for PBAT electrospun filter medium. The relation between filter membrane morphology and facemask performance indicates that a smaller diameter and uniform morphology results in better filtration and breathability of the facemask filter inserts. [ABSTRACT FROM AUTHOR]

AbstractThe COVID-19 pandemic triggered a surge in demand for N95 or equivalent respirators that the global supply chain was unable to satisfy. This shortage in critical equipment has inspired research that addresses the immediate problems and has accelerated the development of the next-generation filtration media and respirators. This article provides a brief review of the most recent work with regard to face respirators and filtration media. We discuss filtration efficiency of the widely utilized cloth masks. Next, the sterilization of and reuse of existing N95 respirators to extend the existing stockpile is discussed. To expand near-term supplies, optimization of current manufacturing methods, such as melt-blown processes and electrospinning, has been explored. Future manufacturing methods have been investigated to address long-term supply shortages. Novel materials with antiviral and sterilizable properties with the ability for multiple reuses have been developed and will contribute to the development of the next generation of longer lasting multi-use N95 respirators. Finally, additively manufactured respirators are reviewed, which enable a rapidly deployable source of reusable respirators that can use any filtration fabric.Graphic abstract

The World Health Organization and the United States Centers for Disease Control have recommended universal face masking by the general public to slow the spread of COVID-19. A number of recent studies have evaluated the filtration efficiency and pressure differential (an indicator of breathability) of various, widely available materials that the general public can use to make face masks at home. In this review, we summarize those studies to provide guidance for both the public to select the best materials for face masks and for future researchers to rigorously evaluate and report on mask material testing. Of the tested fabric materials and material combinations with adequate breathability, most single and multilayer combinations had a filtration efficiency of

Introduction: The important parameters for evaluating the performance of particle filtering respirators in international standards are the filtration efficiency and respiratory resistance of the mask filter against airflow passage. To improve nanofiber filtration efficiency while creating the least breathing difficulty for the wearer, various research has been or is being conducted worldwide. This study investigated the effect of using polyacrylonitrile (PAN) nanofiber composite membrane and montmorillonite clay nanoparticles (MMT) in enhancing particle-filtering respirators’ filter performance, achieving higher filtration efficiency while maintaining optimal respiratory resistance conditions. Material and Methods: First, PAN polymer solution containing zero, 1%, 2%, 3%, and 5% MMT nanoparticles was prepared, and then PAN/MMT nanofiber composite membrane was synthesized in an electrospinning machine. Filtration efficiency was measured in diameter range of 0.3, 0.5, 1, and 3 microns using sodium chloride aerosol. Additionally, filter breathing resistance was measured at flow rates of 30, 85, and 95 liters per minute. Results: The efficiency of synthesized composite nanofilters for particle purification can be improved by adding MMT nanoparticles to PAN nanofibers. Optimal MMT concentration was found to be 2%. This addition resulted in an increase in filtration efficiency for particles with sizes of 0.3, 0.5, 1, and 3 microns by 4.2%, 4.88%, 3.77%, and 2.75% respectively without causing significant difference in respiratory resistance. Improved filtration efficiency can be attributed to enhanced morphology of composite nanofilters resulting from addition of MMT nanoparticles. Adding 2% MMT nanoparticles to PAN nanofibers resulted in uniform distribution and smaller fiber dimensions which did not significantly affect Packing density and porosity. Conclusion: If 2% of MMT nanoparticles are added to PAN nanofibers and used to produce particle respirators, resulting respirator will exhibit a 4.2% increase in particle filtration efficiency without increasing breathing difficulty for user. This result can help protect users from particulate pollutants in air pollution conditions.

With the aggravation of environmental pollution and the worldwide epidemic of infectious diseases, there is a higher demand for air filtration materials to intercept fine particulate matter and capture biological pollutants. Polypropylene (PP)/polycarbonate (PC) blends were melt blown and electrospun with polytetrafluoroethylene (PTFE) on their surfaces. The PP/PC/PTFE membranes structure with micro-nanostructure was constructed through the melt-blown layer with micron structure and the electrospun layer with the nanostructure. Carboxymethyl chitosan (CMCS) was loaded onto the surface of the PP/PC melt-blown layer. The synergistic effect of micro-nanostructure and CMCS can effectively capture PM2.5 and make the composite membrane have excellent antibacterial performance. The inhibition rates of PP/PC/PTFE composite membrane loaded with 5% CMCS against Staphylococcus aureus and Escherichia coli reached 81.54% and 86.1%, respectively. The filtration efficiency of PP/PC/PTFE composite membrane loaded with 5% CMCS is close to 100% for 0.25 μm particles, and the average filtration efficiency for 0.200–4.596 μm and 0.200–2.500 μm particles is 97.31% and 97.27%, respectively. After washing and drying five times, the corresponding inhibition rate only lost 16.52% and 4.24%. The micro/nano structure composite membrane prepared in this study has good antibacterial performance, high filtration efficiency, good stability, and is an excellent antibacterial high efficiency air filter. It provides a new idea for the preparation of air filter fiber composites.

Some users consider modern hydrostatic drives and controls to be unreliable and difficult to maintain. This view is often due to operational problems caused by issues with obtaining and then maintaining the appropriate cleanliness class of the working fluid. Recommendations on the selection of appropriate filtration system elements can be found in the literature, but there is no numerical model that could be helpful in a detailed analysis of the phenomenon. In the article, the authors tried to fill the research gap regarding the lack of a filtration model based on the filtration efficiency coefficient of filter elements used in hydraulic drives and controls. The developed model allows users to determine the influence of selected filtration system parameters on the separation of contaminants by filter elements. The model is intended to help designers and users of hydraulic drives and controls in optimizing the filtration system in order to obtain and then maintain the required cleanliness class of the hydraulic fluid. This paper also includes the results of the sensitivity analysis of selected filtration-system operating parameters in terms of the highest efficiency. In order to verify the developed model, experimental tests were also carried out, with the results presented in this paper. Based on the numerical analyses and experimental studies, recommendations that may be helpful in the selection or development of filtration systems used in hydrostatic drives and controls were developed.

The filtration efficiency of cloth masks for small harmful particles is usually low because of the large pore size of fabrics and the difficulty to choose appropriate fabric specifications. In this study, the polymers with antibiotic groups of quaternary amines were grafted onto cotton fabrics for achieving both satisfactory antibiotic and filtering performance. The results indicated that the pore size of the fabrics grafted with polymer brushes was significantly reduced and thus the filtration efficiency of polymer-grafted cotton fabrics can be increased to 81.5% ± 7.8% from 17.5% ± 2% of original fabrics under the tested level of 0.3 μm particles with 85 L/min flowing rate. The filtration efficiency of treated fabrics was comparable to the medical masks currently used in clinic. Moreover, the grafted fabrics also exhibited excellent antibacterial performance and washability. After 20 cycles of washing, they still had about 75.9% filtration efficiency and 99.9% bacterial inhibition rate for E. coli. This work could inspire the development of reusable and sustainable facemasks with effective personal protection for reducing the spread of COVID-19 and other infectious diseases. [ABSTRACT FROM AUTHOR]

Based on the theory of spherical filled bed, the internal porous media filter wall of the Diesel Particle Filter (DPF) is assumed to fill the filter wall of the unit cell. Since particle trapping by DPF is a dynamic process, the particle deposition characteristics inside DPF are simulated by numerical simulation in this paper. The influence of macroscopic incoming flow parameters and microstructural parameters on DPF filtration performance is investigated, and then the optimization window that can improve DPF filtration performance is explored. The results show that increasing the exhaust temperature and incoming particle concentration leads to an increase in the filtration efficiency and pressure drop of DPF, while the higher the filtration velocity, the lower the filtration efficiency of DPF. In addition, the larger the porosity, the higher the filtration efficiency and pressure drop of DPF, while the increase in the average pore size and pore size distribution range leads to a decrease of the filtration performance of DPF. On this basis, evaluation indexes that can evaluate the filtration performance of DPF are proposed to provide a theoretical basis for optimizing the substrate parameters of DPF. [ABSTRACT FROM AUTHOR]

Diesel particulate filter (DPF) is one of the effective technologies for controlling vehicle particulate matter (PM) emissions. In this research, a hybrid multi-objective optimization approach of FGRA-RSM-MOPSO was developed for DPF, with optimization objectives including maximum initial filtration efficiency and minimum pressure drop. Decision variables include diameter, length, wall thickness, porosity, and pore diameter. Firstly, a computational fluid dynamics (CFD) model for DPF was established, and sensitivity analysis of DPF structural parameters was conducted through fuzzy grey relational analysis (FGRA) to screen out key factors affecting DPF trap performance. Then, response surface methodology (RSM) was used to establish the mathematical relationship between key structural parameters, initial filtration efficiency, and pressure drop. Finally, multi-objective particle swarm optimization (MOPSO) is used to optimize the target and select the optimal solution from the Pareto front. Compared with the original DPF, the optimized DPF under standard operating conditions increased the initial filtration efficiency by 46.85% and reduced the pressure drop by 34.88%. The optimization effect is more pronounced under high load conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Air filtration is an urgent global need because, in many countries and regions, the high concentration of inhalable suspended particles in the air is causing irreversible damage to human health. The use of nanofibrous membranes can help to reduce airborne particulate matter because of their large surface area, extremely porous structure, and adjustable pore size. However, despite their unique properties, the main drawbacks of nanofibre membranes are their poor mechanical properties. This review focuses on nanofibrous membranes prepared by electrospinning, a versatile technique in which the process parameters allow control of the morphology and dimensional characteristics of the nanofibres. Recent literature on air filtration is reviewed, focusing on the performance of materials such as pure or mixed polymers, organic–inorganic composites, and 'green' materials in the form of nanofibrous membranes. Finally, the recently proposed layered structures for nanofibre-based air filters are reviewed, offering the latest and most innovative solutions. [ABSTRACT FROM AUTHOR]

The present study proposes a new design of mechanical filter to suit the recirculating aquaculture system (RAS) as a high-efficiency alternative filter to the conventional swirl separator (CSS). The new filter is considered the developed version of CSS; thus, it is called thereafter as the swirl-vertical drum filter (SVDF) which is provided with a rotating vertical micro-screen drum equipped with a fixed vertical brush as a self-cleaning tool instead of the conventional backwash system. The performance of SVDF was evaluated under different drum rotational speeds, and drum rotation times using sinking and floating fish feed pellets and magnetic field device, and then, it was compared to CSS in terms of water quality and filtration efficiency under the same operational conditions. Experimental results showed better values of water quality including Dissolved oxygen (DO), pH and unionized ammonia (NH3). Also, the lowest value of COD was found to be 18.33 mg/L by using SVDF with floating feed pellets, whilst the highest value of 100.73 mg/L was found in the case of using the CSS with sinking pellets. Meanwhile, the magnetic field device had no effect on the filtration process. The lowest surface area of the vertical micro-screen drum of 0.217 ± 0.013 m2 was obtained at the drum's rotational speed of 20 rpm (0.39 m/s), rotation time of 150 min with floating feed pellets. Experimentally, it is found that the new SVDF has higher filtration efficiency than the CSS by about 57.57% under the same operational conditions. [ABSTRACT FROM AUTHOR]

Currently, Particulate Number (PN) is regulated under EURO 6d regulation in Europe, and even stricter regulation (EURO 7) is under discussion by Advisory Group on Vehicle Emission Standards (AGVES) in European Commission considering the Real Driving Emission (RDE) [1]. The Gasoline Particulate Filter (GPF) is used to reduce such particulate emission, and the catalyst can be coated inside or on the substrate wall to add the Three-Way Catalyst (TWC) function to purify the toxic gases. High PN emission from the Direct Injection engine was observed especially at the cold-start region and the high-load (high speed & acceleration) condition, and Mitsui Kinzoku's unique On-wall coating technology enabled the very high PN filtration efficiency (FE) even with such severe RDE condition. In this paper, the filtration mechanism of Mitsui Kinzoku's unique On-wall coated GPF and the typical In-wall coated GPF was studied by the simulation software using the condition imitating the actual RDE mode. [ABSTRACT FROM AUTHOR]

• Using a customized set-up employing an Electrical Low Pressure Impactor, the size-specific filtration efficiency, pressure drop, and filter quality of children's masks (surgical, KN95, 100% cotton, and partially-cotton-based masks) were tested at face velocities representative of adults and school-aged children. • As with adults' masks, children's nonwoven masks (such as surgical and KN95) showed a higher filtration efficiency and filter quality than woven masks. • In accordance with the single fiber theory, the lower face velocity for school-aged children yielded a higher filtration efficiency and lower pressure drop, but FE at particle sizes larger than 0.04 µm was low for woven masks. Differences in physiology and breathing patterns between children and adults lead to disparate responses to aerosols of varying sizes. No standardized method exists for measuring the filtration efficiency (FE) of children's masks to reflect such differences. Using an adult N95 mask as a control and two different face velocities (v f) (9.3 cm/s representing adults and 4.0 cm/s representing school-aged children), we tested the pressure drop (ΔP) through children's nonwoven masks (surgical and KN95) and children's woven masks (100% cotton and partially-cotton-based masks), as well as their size-specific FE between aerodynamic particle diameters of 0.02 and 2.01 μm. All three types of mask showed a 1 to 9% absolute increase in minimum FE at the lower v f and a significant decrease in ΔP. For children's surgical masks the increase in FE was significant for most of the examined particle sizes, but for children's woven masks the increase was limited to particles smaller than 0.04 μm. Lower v f for children is likely to lead to a higher FE, lower ΔP, and consequently higher filter qualities in children's masks. For woven masks, the FE for particles larger than 0.04 μm was low (typically <50%) for both v f 's studied. [ABSTRACT FROM AUTHOR]