Urbanization increased population density in cities and consequently leads to severe indoor air pollution. As a result of these trends, the issue of sustainable and healthy indoor environment has received increasing attention. Various air filtration techniques have been adopted to optimize indoor air quality. Air filtration technique can remove air pollutants and effectively alleviate the deterioration of indoor air quality. This paper presents a comprehensive review on the synergistic effect of different air purification technologies, air filtration theory, materials and standards. It evaluated different air filtration technologies by considering factors such as air quality improvement, filtering performance, energy and economic behaviour, thermal comfort and acoustic impact. Current research development of air filtration technologies along with their advantages, limitations and challenges are discussed. This paper aims to drive the future of air filtration technology research and development in achieving sustainable and healthy building ventilation.
All content in this area was uploaded by Derek John Clements-Croome on May 08, 2022
Content may be subject to copyright.
A preview of the PDF is not available
... Particles suspended in the air are attracted and captured by the static load when the air passes through the cross-linked fibrous structure of the filter, as these fibers are susceptible to electrostatic loads. According to various estimates, depending on the ionizing power and filter types, the efficiency of filtration with electrostatic filters ranges from 82% to 94% [72,73]. The disadvantage of this solution lies in the fact that electrostatic filters operate in a manner that forces particle ionization, which is directly associated with the emission of ozone (O 3 ) and nitric oxide (NO x ) . ...
... Apart from the aforementioned user health and safety limitations, the primary disadvantage associated with using these devices is the fact that household solutions usually feature low ionization levels, and hence, a considerably lower air-filtering efficiency. That is why these filters are most commonly used as one of several combined indoor air purification stages in air-cleansing devices, e.g., in combination with mechanical filtration or photocatalytic processes [72,74]. ...
Aims: With the ongoing pandemic and increased interest in measures to improve indoor air quality, various indoor air purifiers have become very popular and are widely used. This review presents the advantages and disadvantages of various types of technologies used in air purifiers in terms of reducing microbial contamination. Methods: A literature search was performed using Web of Science, Scopus, and PubMed, as well as technical organizations dealing with indoor air-quality to identify research articles and documents within our defined scope of interest. Relevant sections: The available literature data focus mainly on the efficiency of devices based on tests conducted in laboratory conditions with test chambers, which does not reflect the real dimensions and conditions observed in residential areas. According to a wide range of articles on the topic, the actual effectiveness of air purifiers is significantly lower in real conditions than the values declared by the manufacturers in their marketing materials as well as technical specifications. Conclusions: According to current findings, using indoor air purifiers should not be the only measure to improve indoor air-quality; however, these can play a supporting role if their application is preceded by an appropriate technical and environmental analysis considering the real conditions of its use.
... Air filtration technology (such as stretched membrane filtration, electrostatic capture filtration and fiber filtration) can play an essential role in improving IAQ and protecting human health; it can be captured PM and airborne microorganisms simultaneously . In order to protect human health, various air purification products have been produced. ...
Particulate matter and airborne microorganisms are two of the most severe indoor air problems due to their significant risks to human health. Comprehensive research on air filtration with good filtration performance for fine particles and antibacterial function is essential. In this study, after some experimentations and optimization of conditions, polyacrylonitrile (PAN) 10–1% silver nanoparticles (AgNPs) membranes with suitable morphology and uniform diameter distribution are fabricated by an electrospinning method. These electrospun mats exhibited antibacterial activity toward Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria). With its small pore size, high porosity, the high specific surface area of 42 m²/g, and robust mechanical strength of 7.14 MPa properties, the resultant PAN10%-1%Ag membranes exhibit high filtration efficiency of 99.27%, the low pressure drop of 33 Pa, and higher quality factor compared to the two standard commercial masks including, the three-ply surgical mask and the respirator face mask. After 24 h of the filtration process in a simulated living environment, the obtained air filter still displayed a high filtration efficiency and a less pressure drop variation. In addition, the R² value was 0.99, which indicates that the calculation results are in good agreement with the measured results. The fabrication of PAN-Ag membranes will have broad applications, including face masks, indoor air filtration and clean room.
... In 2015, the World Health Organization (WHO) and the Organisation for Economic Cooperation and Development (OECD) identified air toxins as the form of air pollution that had the greatest impact on health . Outdoor air pollution is now the fourth leading mortality risk worldwide, preceded only by high blood pressure, dietary risk, and smoking [1,2]. Exposure to atmospheric pollution occurs at all hours of the day encompassing where an individual lives and works. ...
Nitrogen oxides (NOx) are gaseous pollutants contributing to pollution in their primary form and are also involved in reactions forming ground-level ozone and fine particulate matter. Thus, NOx is of great interest for targeted pollution reduction because of this cascade effect. Primary emissions originate from fossil fuel combustion making NOx a common outdoor and indoor air pollutant. Numerous studies documenting the observed physical health impacts of NOx were reviewed and, where available, were summarized using risk ratios. More recently, the literature has shifted to focus on the mental health implications of NOx exposure, and a review of the current literature found five main categories of mental health-related conditions with respect to NOx exposure: common mental health disorders, sleep, anxiety, depression, and suicide. All the physical and mental health effects with available risk ratios were organized in order of increasing risk. Mental health concerns emerged as those most influenced by NOx exposure, with physical health impacts, such as asthma, only beginning to surface as the fourth highest risk. Mental health conditions occupied seven of the top ten highest risk health ailments. The results summarized in this narrative review show that there are clear positive correlations between NOx and negative physical and mental health manifestations, thus strengthening the argument in support of the reduction in ambient NOx levels.
... Viral particles with smaller diameters, such as the inuenza virus (approximately 100 nm), can penetrate through highefficiency particulate air (HEPA) lters because these lters only have the ability to block the passage of particles with a diameter greater than 0.3 mm. 37 To increase the ltration efficiency, tannic acid (TA), a plant-derived polyphenol with antiviral activity, was used for functionalization of HEPA lters as a cost-efficient adhesive with the capability of trapping viruses via affinity binding (Fig. 3). 38 Furthermore, AgNP-coated HEPA lters display a decreased ltration quality factor and a decreased antiviral quality factor (0.05-0.08 Pa À1 ) with increased dust loading according to a previously established mathematical model, 39 as dust particles tend to prevent direct contact of AgNPs with viral particles, giving rise to a decrease in the antiviral activity. ...
COVID-19 persists as the most challenging pandemic of the 21st century with a high rate of transmission. The main pathway of SARS-CoV-2 transmission is aerosol-mediated infection transfer through virus-laden droplets that are expelled by infected people, whereas indirect transmission occurs when contact is made with a contaminated surface. This mini review delivers an overview of the current state of knowledge, research directions, and applications by examining the most recent developments in antiviral surface coatings and filters and analyzing their efficiencies. Reusable masks and other personal protective devices with antiviral properties and self-decontamination could be valuable tools in the fight against viral spread. Moreover, antiviral surface coatings that repel pathogens by preventing adhesion or neutralize pathogens with self-sanitizing ability are assumed to be the most desirable for terminating indirect transmission of viruses. Although many nanomaterials have shown high antiviral capacities, additional research is unquestionably required to develop next-generation antiviral agents with unique characteristics to face future viral outbreaks.
... There are various ways to reduce indoor air pollution. These ways include: removing pollution at source ; reducing indoor pollutants using air-cleaning technologies, such as biological filtration and plant systems for indoor air purification [1,21,22], and using air purifiers to absorb and filter organic pollutants ; improving living conditions by optimizing ventilation and air conditioning systems [24,25]; and reducing smoke exposure by improving kitchen design and changing cooking methods . While reducing sources of contamination is generally the preferred method, it is often difficult to achieve. ...
Indoor air pollution is injurious to human health, even worse than outdoor air pollution. However, there is a lack of empirical evidence using large samples in developing countries regarding whether indoor air purification can improve human health by reducing indoor air pollutants. Using the data from the China Health and Nutrition Survey in 2015, this study analyzes the relationship between indoor air purification and residents’ self-rated health. We apply the generalized ordered logit model and find that indoor air purification has a significantly positive effect on residents’ self-rated health. This positive effect is limited to improving the probability of residents’ health level being rated “good”, and there is no significant movement between the two levels of “bad” and “fair”. The results also show that, as an important source of indoor air pollutants, solid fuels used in cooking significantly reduced residents’ self-rated health level. Additional results show the heterogeneity of the relationship between indoor air purification and resident health among groups with different characteristics. This study provides empirical evidence for further optimizing the indoor air environment.
The application of photocatalytic oxidation (PCO) in air purifiers (AP) to remove viruses, bacteria, and toxic gases in the air is intensively being studied, especially after the Covid-19 pandemic broke out. The testing method of PCO materials for AP purposes has been standardized through ISO 22197-4 (2013). However, the standard required a set of complex, high precision, and costly equipment. The present study demonstrates a simpler and low-cost test setup without compromising any accuracy in the overall result. The proposed test consists of a test chamber and mixing chamber, and sets of equipment installed in it. A 3D printer fabricated a PCO reactor, and TiO 2 was coated on the surface. Formaldehyde (HCHO) is used as a sample pollutant to be observed, injected into the test chamber. Before the measurement of the concentration of HCHO, the intensity of UV A LED was measured. Then, the amount of formaldehyde concentration was monitored online by indoor air quality measurement equipment. The result shows that the intensity of UV light was enough to generate a photocatalytic oxidation reaction. After 20 minutes of reaction, the HCHO concentration inside the chamber was decreased around 21.76%.
We model porous membrane filters as networks of connected cylindrical pores via a random network generation protocol, and their initial pore radii via a uniform distribution of widths that vary about some mean value. We investigate the influence of network and pore size (radius) variations on the performance of membrane filters that undergo adsorptive fouling. We find that membrane porosity variations, independently of whether induced by variations of the pore radii or of the random pore network, are an important factor determining membrane filter performance. Network and pore size variations still play a role, in particular if pore radii variations are significant. To quantify the influence of these variations, we compare the performance metrics of networks built from pores of variable radii to their (equal porosity) counterparts built from pores of uniform radius. We show that the effect of pore radii variations is to increase throughput, but also to reduce foulant control.
Air pollution control has been a recurrent challenge, given the several harmful effects on human health and the environment. Indoor air quality is an issue that needs attention due to the long-time people spend in indoor environments and the various industrial processes that require clean air in these places. In recent years, there has been an increase in innovative technologies capable of retaining fine particles, including microorganisms, such as the new coronavirus-2019. This brief review presents the development, use, and perspectives regarding electrospun nanofibers as air filter media, considering the unbelievable impacts arising from COVID-19. We remark that nanofiber filters produced by electrospinning are an efficient alternative for controlling nanometric bioaerosols and other hazardous pollutants in indoor environments since it is possible to combine desirable characteristics to control them. Finally, we recommend a better collaboration between academia and industry to accelerate the technology transfer processes.
Air pollution is a serious health concern that affects many people across the globe. The major air pollutants are particulate matter, carbon oxides, nitrogen oxides, sulphur oxides, volatile organic compounds, polycyclic aromatics and free radicals which cause severe respiratory distress and infections. The existing air cleaning systems suffer from drawbacks of high cost and generation of secondary pollutants. A novel biological air filter “Biosmotrap” which is a laminate composite of sponge gourd and algae was developed. Biosmotrap placed in a carrier assembly on exhaust of vehicles, could remove carbon monoxide, nitric oxide, nitrogen dioxide, and fine particulate matter (PM2.5) from the vehicular emissions resulting in cleaner emissions. Biosmotrap decreased carbon monoxide from 1,423,992 μg/m³ to 76,756 μg/m³, nitric oxide from 71,128 μg/m³ to 9982 μg/m³, nitrogen dioxide from 565 μg/m³ to 188 μg/m³ and PM2.5 from 3200 μg/m³ to 60 μg/m³ from a polluting vehicle. Biosmotrap removed 60–80% of indoor pollutants from cigarette smoke and incense-stick smoke. Biosmotrap could protect the human cells from oxidative DNA damage induced by indoor air pollutants. Hibiscus rosa-sinensis plants exposed to air filtered through Biosmotrap were healthy as compared to the plants directly exposed to polluted air. Biosmotrap is an economic, efficient, eco-friendly filter that is superior to existing air filtration methods.
To overcome the excessive heat in tropical climate countries during the day, the types of skin or façade play a vital role in regulating the temperature and the amount of heat transmission in a building. This research was carried to evaluate the percentage of temperature reduction of two building samples, one with “vertical greening” and one without. The result proved that the temperature reduction of the building with the green façade system is higher than the building without the green façade system. Therefore, it justifies that Vertical Greening Facade does act as an acceptable passive approach for sustainable design.
The number-one environmental threat to public health, air pollution remains a pressing problem-made even more complicated by the massive quantity and diversity of air pollution sources. Biofiltration technology (using micro-organisms growing on porous media) is being recognized as one of the most advantageous means to convert pollutants to harmless products. Done properly, biofiltration works at a reasonable cost-utilizing inexpensive components, without requiring fuel or generating hazardous by-products. Firmly established in Europe, biofiltration techniques are being increasingly applied in North America: Biofiltration for Air Pollution Control offers the necessary knowledge to "do it right."
This work deals with development, characterization, and application of triboelectrically charged nonwoven electrets. The electrets were prepared using wool and polypropylene fibers and employing needlepunched nonwoven technology. It was observed that the magnitude and duration of electret charge increased with a decrease in diameter of wool and polypropylene fibers. The charge was found to decay double exponentially, presumably due to quick decay of surface charge and slow decay of bulk charge. The charge in tribocharged electrets was utilized to capture hazardous particles from the air stream very efficiently. The electret media exhibited remarkably higher filtration efficiency than the uncharged media.
In this study, a dielectric barrier discharge (DBD) non-thermal plasma experimental set-up is utilized to investigate the effect of design parameters including the configuration and type of electrodes as well as the size of the reactor on the energy consumption and the rate of ozone generation. Results show that increasing the residence time by applying a larger length of the inner electrode causes an earlier plasma ignition, as well as formation of larger amounts of ozone for a given specific input energy (SIE). Changing the configuration and the type of the ground electrode shows that this electrode configuration is a dominant parameter for enhancing the energy yield in the plasma reactor. Furthermore, it was noted as the size of the reactor is increased, by increasing the gap between the electrodes, higher level of SIE is needed to reach the same level of ozone concentration.
Fibrous media is the most common method of filtration, which is generally characterized by its pressure drop and filtration efficiency. In this work, the computational fluid dynamics (CFD) technology was applied to simulate the filtration performance of multi–fiber filters. The pressure drop and filtration efficiency with different fiber arrangements, fiber diameters, face velocities and particle sizes were studied. It was found that filtration efficiency changed with the face velocity for different particle sizes. The layered structures with the same fiber diameters and total solid volume fraction (SVF) were compared, indicating that the dense–sparse structure had the highest filtration efficiency for all the simulated particle sizes at the cost of high pressure drop. Then the dense–sparse structure was optimized to achieve a better filtration performance by using less tiny fibers in the front–row and removing some fibers in the back–row.
Living walls are systems that allow the development of vegetation in a vertical surface attached to building facades or indoor walls. Traditionally, they have behaved as ‘passive’ bio-filters, but new approaches and technologies are moving towards their integration within the building's air conditioning and ventilation systems. In an Active Living Wall (ALW), air is forced to pass through the vegetated wall to take advantage of their evaporative cooling potential as well as the capacity of these biological systems to purify air. In the case of indoor ALWs, air is cooled, bio-filtered and humidified thus potentially reducing ventilation requirements. This work describes a prototypic indoor ALWs installed at the University of Seville (Spain). Preliminary results of its performance on indoor air conditions (temperature and humidity) are presented and discussed. Drops in temperature between 0.8 and 4.8 °C have been observed at different distances from the ALW. The cooling process was more efficient when the initial conditions of the room were drier and warmer.
Background: Storage of fruit, vegetables and other products is used worldwide with a wide variety of foods. In many cases, though environmental conditions such as air humidity and temperature are taken into consideration, air filters are not employed even though such filters could potentially reduce the perishing of product during storage. Scope and approach: The purpose of this review is to list and evaluate currently available air filtration technologies, in order to determine their suitability for use inside food storage warehouses. Factors such as pressure drop, running costs, and the environmental conditions which the filters will be operating in need to be taken into consideration. Key findings and conclusions: A number of physical filters, i.e., HEPA, glass fiber, PTFE and cellulose filters as well as polyurethane foams and nanofiber mats are presented first. These are filters which function by providing a physical barrier which particles cannot pass through, or which particles stick to. These are followed by a discussion of other, non-physical methods, such as electrostatic precipitation, cold plasma, wet scrubbing, cyclonic air filtration, UV radiation (and coatings), fumigation, nanoparticles bound on filter media, which are either commonly employed in industry, or are interesting emerging technologies.
In order to enhance the photocatalytic indoor air purifying efficiency, the photocatalytic technology was combined with non-thermal plasma to improve the removal of indoor air contaminants. The experimental results show that the removal rate of formaldehyde is improved sharply by plasma and photocatalysis. The removal rate of formaldehyde is increased with the increasing of excited voltage for plasma and the removal of contaminants has the maximal value under the optimal excited voltage in this paper. So the combination of photocatalysis with plasma is an applying direction of photocatalytic technology for air purification.