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Tested full-scale bag filters and their properties. Pressure drops were measured at 0.944 m 3 /s Filter class
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Neither the European standard nor the US standard for classification of intermediate class filters comprises testing of filter performance with respect to ultrafine particles (UFPs) or particles of the most penetrating size (MPPS). This could turn out to be a major lack in classification standards since UFPs have been pointed out as a serious healt...
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... new full-scale bag filters, provided by three major Swedish and international filter manufacturers, were tested in a full-scale test rig. Properties of the full-scale filters are shown in Table 1. The filters were of class M5, M6, and F7-F9, accord- ing to the European filter standard EN 779:2012. ...
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... The filtration performance of air filters varies according to the air velocity and therefore the air flowrate. 69 A digital pressure manometer was used to measure pressure drop of the filter while an anemometer was used to measure the air velocity in this work. Under low air velocity, low pressure drops were measured as 6.89 and 41.36 Pa for MDNM and HEPA filter, respectively. ...
Air pollution is a problem that is increasing day by day and poses a threat on a global scale. Particulate matter (PM) is one of the air pollutants that is the biggest concern regarding air quality. In order to control PM pollution, highly effective air filters are required. This is especially necessary for PM with a diameter of less than 2.5 micrometers (PM2.5), which poses a health risk to humans. In this study, we demonstrate for the first time the use of a two-dimensional titanium carbide (Ti3C2) MXene nanosheets-decorated nylon mesh (MDNM) as a low cost and highly efficient PM2.5 filter. This study develops a proof-of-concept method to capture PM2.5. Thanks to their high specific surface area and active surface-terminating groups, conductive MXene nanosheets have made nylon mesh filters promising candidates for air filtration. The developed filters used electrostatic force to capture PM2.5 and showed high removal efficiency (90.05%) when an ionizer was used and under an applied voltage of 10 V, while a commercial high-efficiency particulate air (HEPA) filter had a removal efficiency of 91.03% measured under identical conditions. The proposed filters, which stand out with their low energy consumption, low pressure drop (∼14 Pa), and cost-effectiveness, have the potential to be a strong competitor to conventional PM filter systems used in many fields.
... There are several methods to evaluate air purifiers, including animal experiment [38] as well as laboratory-based test chambers [39,40]. To determine the efficacy of the air purifier, the samples collected upstream and downstream of the air purifier can be tested for the presence of infectious pathogens based on cell culture system. ...
The importance of air purifiers has increased in recent years, especially with the "coronavirus disease 2019" pandemic. The efficacy of air purifiers is usually determined under laboratory conditions before widespread application. The standard procedure for testing depends on virus cultivation and titration on cell culture. This, however, requires several days to deliver results. The aim of this study was to establish a rapid molecular assay which can differentiate between intact infectious and distorted non-infectious virus particles. Feline Coronavirus was selected as model for screening. First the samples were pretreated with enzymes (universal nuclease and RNase cocktail enzyme mixture) or viability dye (propidium monoazide) to eliminate any free nucleic acids. The ribonucleic acid (RNA) from intact virus was released via magnetic beads-based extraction, then the amount of the RNA was determined using real-time reverse transcription polymerase chain reaction (RT-PCR) or reverse transcription recombinase-aided amplification (RT-RAA). All results were compared to the infectivity assay based on the calculation of the 50% tissue culture infectious dose (TCID50). The nuclease has eliminated 100% of the free Feline Coronavirus RNA, while propidium monoazide underperformed (2.3-fold decrease in free RNA). Both RT-RAA and real-time RT-PCR produced similar results to the infectivity assay on cell culture with limit of detection of 102 TCID50/mL. Two UV-C air purifiers with prosperities of 100% inactivation of the viruses were used to validate the established procedure. Both real-time RT-PCR and RT-RAA were able to differentiate between intact virus particles and free RNA. To conclude, this study revealed a promising rapid method to validate the efficacy of air purifiers by combining enzymatic pretreatment and molecular assays.
... Two filters' standards are extensively utilized. One of these standards is EN779 and the other is ASHRAE 52. 2 (2007) [2]. In these classifications, for various particle sizes, dissimilar filter classification criteria were used. ...
... The dimension of particles that filters can filter vary in EN779:2012 and ASHRAE 52.2 standards. While 0.4 μm particles can be filtered in EN779:2012, ASHRAE 52.2 filters 0.3 to 10 μm particles [2]. Also, Also, due to the insufficient filtration standards of EN 779:2012, experts recommended a more advanced standard, ISO 16890. ...
... The single fiber hypothesis was put forward by Hinds W.C. (1999). Many theoretical studies have been carried out to ease the correct understanding of the data obtained in the experiment or the measured data [2]. In these theoretical studies, mechanisms such as diffusion, interception, and impact are in examined, electrostatic filtration was not included in the studies [4]. ...
It is necessary to understand the efficiency of the filters, which are the most important part of the ventilation systems, in order to hinder the spreading of the Covid-19 virus. In this article, a model was created using theoretical solutions developed for single fiber efficiency and with this created model, the previous theoretical data were confirmed. Then, the theoretical data in the model created with the experimental data were compared. Also, factors such as fiber diameter, particle diameter, or flow velocity affecting single fiber efficiency were changed and the effects of these parameters were investigated. As a result of this investigation, it was seen that, as the Peclet number increased, the single fiber efficiency decreased, and the efficiency of the single fiber increased when the particle diameter increased. Finally, when the solidity, which can be considered as the fiber density in the filter, increased, the single fiber efficiency increased along with it. When solidity was increased from 0.011 to 0.03, single fiber efficiency increases from 0.023 to 0.0269. That is, there was an increase of approximately 16.9 %.
... At the same time, the filters can deal with high concentrations of PM 10 or PM 2.5 , and they exhibit a very high dust-holding capacity (DHC). 13 According to the research of Shi et al., 14 Hinds and Kadrichu, 15 and Fisk and Faulkner, 16 the most penetrating particle size (MPPS) for glass fiber is in the range of 0.1-0.3 μm. ...
The airliner cabin environment is very important to the health of passengers and crew members, and the use of high‐efficiency particulate air (HEPA) filters for recirculated air in the environmental control systems (ECS) is essential for the removal of airborne particles such as SARS CoV‐2 aerosols. A HEPA filter should be high efficiency, low‐pressure drop, high dust‐holding capacity (DHC), lightweight, and strong for use in aircraft. We conducted an experimental study on 23 HEPA filters with glass fiber media that are used in different commercial airliner models. The tested filters had a median filtration efficiency of >99.97% for particles with a diameter of 0.3–0.5 μm, a pressure drop of 134–412 Pa at rated airflow rate, and a DHC of 32.2–37.0 g/m2. The use of nanofiber media instead of glass fiber media can reduce the pressure drop by 66.4%–94.3% and significantly increase the quality factor by analysis of literature data. The disadvantages of poor fire resistance and small DHC can be overcome by the use of flame‐retardant polymers and fiber structural design. As a new lightweight and environmentally friendly filter material, nanofiber media could be used as air filters in ECS in the future.
... 9 Experimental measurements of filtration performance on ventilation filters with particles smaller than 0.3 μm have already been presented in several papers. [19][20][21][22][23] Hanley et al. reported that a minimum in efficiency often occurred in the 0.1-0.5 μm diameter size range for in-duct air cleaners. 24 More importantly, the structure of SARS-CoV-2 ranges from 90 to 120 nm, 25 which mainly exists in saliva aerosols; the SARS-Cov-2 RNA has been detected in particles below 0.3 μm. ...
... curred in the 0.1-0.5 μm diameter size range. Shi et al.21 reported that the MPPS for glass fiber filters was observed in the size interval 100-200 nm, while the MPPS for charged synthetic filters was observed in the size interval 40-100 nm. In this study, the lowest removal efficiencies occurred at 0.1-0.4 ...
Particle size removal efficiencies for 0.1–1.0 μm (PSE0.1−1.0$$ {PSE}_{0.1-1.0} $$) and 0.3–1.0 μm (PSE0.3−1.0$$ {PSE}_{0.3-1.0} $$) diameter of Minimum Efficiency Reporting Value (MERV) filters, an electrostatic enhanced air filter (EEAF), and their two‐stage filtration systems were evaluated. Considering the most penetrating particle size was 0.1–0.4 μm particulate matter (PM), the PSE0.1−1.0$$ {PSE}_{0.1-1.0} $$ as an evaluation parameter deserves more attention during the COVID‐19 pandemic, compared to the PSE0.3−1.0$$ {PSE}_{0.3-1.0} $$. The MERV 13 filters were recommended for a single‐stage filtration system because of their superior quality factor (QF) compared to MERV 6, MERV 8, MERV 11 filters, and the EEAF. Combined MERV 8 + MERV 11 filters have the highest QF compared to MERV 6 + MERV 11 filters and EEAF + MERV 11 filters; regarding 50% of PSE0.1−1.0$$ {PSE}_{0.1-1.0} $$ as the filtration requirements of two‐stage filtration systems, the MERV 8 + MERV 11 filtration system can achieve this value at 1.0 m/s air velocity, while PSE0.1−1.0$$ {PSE}_{0.1-1.0} $$ values were lower than 50% at 1.5 m/s and 2.0 m/s. EEAF obtained a better PSE0.3−1.0$$ {PSE}_{0.3-1.0} $$ in the full‐recirculated test rig than in the single‐pass mode owing to active ionization effects when EEAF was charged by alternating current.
... Table 3 lists the device's main characteristics. In the first test, the valve was set to guarantee an air velocity through the filter media equal to 0.45 m/s a value higher than the range of values used by Ref. [39]. In the second and third test, the velocity was 1 m/s. ...
Verifying the capacity of different types of air filters to stop the propagation of the SARS-CoV-2 virus has become a strategic element to contain viral spreading in enclosed spaces. This paper shows the results of experimental tests about the capacity of different commercial filter grades to stop SARS-CoV-2 propagation using inactivated virions. In the first test, the obtained results showed that the F8 filter blocks SARS-CoV-2 propagation if it encounters a flow devoid of liquid phase, i.e., a biphasic flow that can wet the filtering material. On the contrary, as shown in the second test, the SARS-CoV-2 virus propagates through the F8 filter if the droplet content in the air flow is enough to wet it. In these operational conditions, i.e., when the filter is wet by a flow with a high droplet content, the absolute H14 filter was also shown to fail to stop the transmission of the SARS-CoV-2 virus. Lastly, in the third test, the viral load was shown to be stopped when the pathway of the infected droplet is blocked.
... À ce jour, quatre études ont examiné spécifiquement l'efficacité de filtration pour les particules inférieures à 100 nm (Hecker et Hofacre, 2008;Shi et al., 2013;Stephens et Siegel, 2013;Karjalainen et al., 2017). Ils ont tous mesuré uniquement l'efficacité de filtration initiale en fonction de la taille des particules. ...
... À partir de leurs données expérimentales, les auteurs ont développé une équation empirique afin de prédire la performance du filtre pour un MERV donné. Shi et al. (2013) Stephens et Siegel (2013) se sont intéressés à la performance initiale des filtres (media mécaniques et media chargés de façon électrostatique) in situ, pour des particules allant de 5 à 100 nm (aérosol ambiant). Ils ont mesuré la performance de l'unité de traitement d'air en fonctionnement normal, avec une recirculation d'air à 100 %. ...
... Table S1) [31,. Given that standards were published and developed [34][35][36][65][66][67][68][69][70][71], the filter class became the most direct and critical factor for filter selection; however, only a few studies reported on the corresponding filter classes [42,46,54,[59][60][61]63]. Moreover, the sizedependent efficiencies of 70% of the filters in different filter classes were measured more than 10 years ago [46,54], and therefore do not reflect the recent improvements in the manufacturing technique and standards. ...
... In general, the efficiency ranges for the particle removal or UFP removal and MPPS were consistent with those obtained from previous studies [42,46,54,[59][60][61]63], as summarized in the Supporting Information (Figs. S2 and S3). ...
... The pressure drops at various face velocities or filter media face velocities have been extensively reported [42,46,54,[59][60][61]63]. The ratios of the pressure drops to velocities were calculated. ...
Ultrafine particles (UFPs) are produced by human activities in outdoor and indoor environments. It is important to control indoor UFPs for their health effects on human and long duration that people spend indoors. Filtration is important in mechanical ventilation system for UFP removal to reduce human exposure to UFPs. The filtration efficiency for particle removal depends on particle diameter. Thus, we selected nine respective filters and their combinations to measure size-dependent efficiencies for UFP removal and the pressure drops. The 4th-order polynomial equations were developed from fitting results. The total efficiencies for UFP removal were estimated based on the polynomial equations and the measured size distributions of ambient UFPs. The total efficiencies for UFP removal and pressure drops of combinations of fine filters are comparable to those of a single HEPA filter. The application of combinations of fine filters needs further study in the future. The filtration efficiencies of these filters are relatively low, which may be caused by the lack of good tightness and need to be improved in the future.
... However, laboratory tests may not reflect the in situ efficiency of a filter in a home because of variations in loading and system conditions. For instance, some laboratory tests (eg, 9 ) were carried out at a face velocity generally lower than the face velocity in real systems. Researchers have used a variety of field test procedures to determine the in situ efficiency of filters including those which measure particle concentrations upstream and downstream of an installed filter [10][11][12] or the whole house particle loss rates in an indoor environment during different HVAC operation and filter conditions. ...
... However, the efficiency was generally low for ultrafine particles (UFP) with a diameter smaller than 100 nm and decreased for particles smaller than 30 nm for some filters. This trend is consistent with other studies on electret or non-electret particle filters (eg, 5,9,15,23,24 exists around filters which allows upstream particles to travel around the filter to downstream and this phenomenon is discussed in more detail in the Discussion. Another possibility is that fine particles were generated in the air handling unit or resuspended from the surfaces of the heat exchangers and cooling coils during the efficiency tests. ...
High efficiency filtration in residential forced‐air heating, ventilation, and air conditioning (HVAC) systems protects equipment and can reduce exposure to particulate matter. Laboratory tests provide a measure of the nominal efficiency, but they may not accurately reflect the in‐situ efficiency of the filters because of variations in system conditions and changes in filter performance over time. The primary focus of this paper is to evaluate the effective filtration efficiency, which is inclusive of any loading and system impacts, in 21 occupied residential homes through in‐duct concentration measurements. We considered the role of filter media by testing both electret and non‐electret media, as well as the role of loading by considering new and used filters. The results show that filters with higher nominal efficiency generally had higher effective filtration efficiency in the same home. In terms of performance change, there is no significant difference in efficiency between initial and 3‐month non‐electret filters, but the efficiency of electret filters generally decreased over time. However, both nominal efficiency and performance change were vastly overshadowed by the wide variety in loading and system conditions across homes, making it hard to predict filter efficiency in a given home without in‐situ measurements.
... The removal rates measured for super-micron particles are quite similar within the entire 1-10 μm diameter range with a slightly higher decay for the coarse fraction (PM 2.5-10 ) which is the one most influenced by resuspension phenomena. As regards the sub-micron particles, the removal rate of particles smaller than 130 nm is quite similar to the total PNC removal rate (roughly 1 h −1 ), whereas a slightly slower decay was observed for particles larger than 130 nm likely due to the typically reduced filter efficiency in that size range (Shi et al., 2013). The almost constant filtration efficiency of the air purifier in the submicron particle size range is confirmed by the data reported in Fig. 5 where the particle size distributions measured during the NV and NV + AP scenarios in the school gym A (normalized to the median indoor particle number concentrations of Fig. 3) are shown. ...
Indoor school gyms are environments characterized by high concentrations of different airborne particulate and gaseous pollutants. In particular, like other naturally-ventilated school environments, in addition to indoor pollutants children can be exposed to sub-micron particles and gaseous pollutants emitted by outdoor sources and penetrating the building envelope; moreover, high concentrations of super-micron particles can be reached due to the resuspension phenomena related to the physical activity performed therein. The present paper aims to evaluate the effect of different ventilation methods (natural ventilation, manual airing) and the use of air purifiers in reducing the indoor concentrations of different airborne particles and gaseous pollutants in school gyms. To this end, an experimental campaign was performed in two naturally-ventilated school gyms in Barcelona (Spain) of different volumes and different distance to major urban roads. Indoor and outdoor measurements of particle number, black carbon and PM1-10 concentrations were performed as well as indoor measurements of CO2 and NO2 concentrations. The study revealed that the use of air purifiers with windows kept closed (natural ventilation) can lead to a significant reduction in terms of indoor-to-outdoor concentration ratios. In the smaller gym (air changes per hour of the purifiers, ACH, equal to 9.2 h-1) the I/O ratios were reduced by 93% and 95% in terms of particle number and PM1-10, respectively; whereas in the larger school gym (ACH = 1.7 h-1) the corresponding reductions were 70% and 84%. For manual airing scenarios, the effect of the air purifiers on outdoor-generated sub-micron particles is reduced; in particular, for low ACH values (i.e. ACH = 1.7 h-1), the reduction is quite negligible (6%).
