Indoor Air Purification Research Articles

Individual and population level protection from particulate matter exposure by wearing facemasks

Because of the severe air pollution in northern China, facemasks have gained popularity in this area in recent years. Although the results of previous studies have shown the effectiveness of wearing facemasks for intercepting particles, the individual differences and the overall health benefits of wearing facemasks have not been comprehensively documented. In this study, using both model and personal tests under various conditions, we test eight major brands of facemasks for their removal efficiencies (REs) of particulate matter (PM) in six size ranges (from 0.3 μm to >10 μm). The results are used to assess the overall exposure reduction at the individual and population levels in Beijing. We find significant differences in REs among PM sizes, facemask brands, pollution levels, and genders. Combining the information on the usage of various brands, facemask wearing rates, and PM2.5 concentrations in the ambient and indoor air in this area, we evaluate the overall effect of facemask wearing on PM2.5 exposure reduction. It is quantitatively demonstrated that because people spend most time indoors, facemask protection is limited. For facemask wearers, the overall exposure can be reduced by less than 20%, whereas the reduction rate is as low as 2.4 ± 1.6% for the entire adult populations even in the year with the highest level of pollution with an annual mean PM2.5 concentration of 102 ± 98 μg∙m−3. As a strategy of self-protection from long-term exposure to particulate matter, wearing facemasks outdoors is inferior to the installation of indoor air purifiers.

Different effects on anemia of short-term indoor air purifier intervention in housewives: KoCHENS-MOM study

Background Housewives are involved in daily household chores such as cleaning and laundry, thus making them exposed directly to indoor particulate matter (PM) exposure. Indoor PM exposure is a potential factor that increases systemic inflammation and affects hematopoietic action. This study aims to investigate the association between indoor PM and indicators of anemia (Hemoglobin, Mean Cell Volume; MCV, Mean Corpuscular Hemoglobin; MCH, Mean Morpuscular Hemoglobin Concentration; MCHC, Erythrocyte Sedimentation Rate; ESR) during air purifier intervention in housewives. Methods We recruited a total of 300 housewives in Seoul and Ulsan, Republic of Korea. Among them, we analyzed the data of 40 housewives who were subjected to the Air cleaner arbitration. Indoor exposure level of PM2.5 and PM10 of each housewife was analyzed as the adjusted value of the sensor measurement. We also investigated the indicator of anemia such as hemoglobin, MCV, MCH, MCHC and ESR before and after the installation of air purifier for one month. Statistical analysis was performed by multiple generalized linear model (GLM). Results The difference in indoor PM exposure levels by air purifier was related in all anemia indicators (Hemoglobin, MCV, MCH, MCHC and ESR). The decrease in the level of indoor PM2.5 level was associated with a decrease in MCHC (β: -1.39, P = 0.05) and ESR (β : -0.08, P = 0.04). The decrease in level of indoor PM10 level was associated with a decrease in MCVH (β: -2.60, P = 0.05) and ESR (β: -0.16, P = 0.04). Conclusion Our results suggest, that the intervention of indoor air purifier decreases PM exposure and affects the anemia indicators. In addition, we will analyze the effects of the air purifier for about three months. In conclusion, anemia and inflammation can be improved by managing indoor PM exposure

Indoor formaldehyde removal by three species of Chlorophytum comosum under dynamic fumigation system: part 2—plant recovery

Spider plants (Chlorophytum comosum) are known to be among the most common easy mountable indoor plants capable of purifying indoor air by absorbing carbon monoxide, formaldehyde, xylene, and many other hazardous gases. In addition, these plants are non-toxic and safe for pets and children. This project is focused on the investigation of the spider plants' capability of the formaldehyde purification under laboratory-controlled parameters of the indoor air environment. Two scenarios including employment of fresh plants as well as recovered ones damaged by 7-day exposure of formaldehyde were considered. A special attention was made to the investigation of physiological indexes of the plant leaves after damage, and whether the spider plant could be reused after its recovery. The physiological characteristics of the recovery period of potted Chlorophytum comosum immediately after 7 days of fumigation with formaldehyde were studied. Eight physiological indexes of leaves including chlorophyll, free protein, relative conductivity, MDA (malondialdehyde, lipid peroxidation), SOD (superoxide dismutase), POD (peroxidase), T-AOC (total antioxidant capacity), and stomata were selected to monitor plants' recovery processes. The results of 30-day experimental runs showed that three species of spider plants were mostly recovered within 15 days. Repeated 7-day fumigation of plants, conducted to study their ability to effectively clean the air after regeneration, confirmed such ability; the efficiency at the first day was similar to the performance of the fresh plant. However, from the second day, the efficiency was dropped by 35-50% and remained at these levels for the rest of the exercise.

Sensitisation of severe asthma in different occupations: A multicentre study in China.

This was the first multicentre study assessing the sensitisation patterns in patients with severe asthma by different occupations as well as different regions of China, and aimed to provide evidence for the prevention of sensitised patients with severe asthma. A total of 676 adults were included and assigned to three cohorts. Cohort A was comprised of severe asthma patients without smoking (n=454), cohort B comprised severe asthmatic patients who were ex-smokers (n=149), and cohort C comprised non-asthma individuals (n=73). All study subjects underwent testing of serum sIgE level of house dusts mix (hx2), foods mix (fx5), moulds mix (mx2), tree pollen mix (tx4) and weed pollen mix (wx5) simultaneously. Overall, the positive rates of hx2, fx5, mx2, tx4 and wx5 were 37.6%, 11.9%, 16.6%, 9.0% and 9.5% in severe asthmatic patients, respectively. Comparing cohort A with cohort B, the hx2 positive rates in cohort A were higher in fulltime homemaker (30.0% vs. 0.0%) and medical staff (40.0% vs. 0.0%, P<0.05). However, the mx2 positive rates in cohort B were higher in businessman (30.0% vs. 7.0%) and the tx4 positive rates in cohort B were higher in drivers (35.7% vs. 0.0%, P<0.05). The optimal scale analysis showed that severe asthmatic patients who work indoor were more prone to be allergic to house dusts (Cronbach's alpha=76.4%). Patients with severe asthma in different occupations exhibited different sensitisation patterns. Avoid being contact with house dust and application of indoor air purifier should be considered for severe asthma patients.

Defect Engineering and Synergistic Effect in Co3O4 Catalysts for Efficient Removal of Formaldehyde at Room Temperature

The inherent low activity at room temperature has greatly limited the utilization of Co3O4 in indoor air purification. In this work, an extremely facile and mild method utilizing the strong oxidati...

Vertical macro-channel modification of a flexible adsorption board with in-situ thermal regeneration for indoor gas purification to increase effective adsorption capacity

Adsorption has been used widely to remove indoor volatile organic compounds (VOCs). However, the large diffusion resistance inside traditional granular adsorbents renders a low VOC adsorption rate. This study proposes a modified method to achieve the rapid diffusion into the adsorbent during the initial adsorption period. A thin and flexible adsorption board with a layer of adsorbent coated on a heating film was prepared for in-situ adsorption and regeneration. Then, regular, vertical macro-channels through the adsorption board were fabricated by laser drilling to enhance mass transfer inside the board. Experimental results demonstrated that after modification, the penetration times for formaldehyde and xylene extended from 3.8 to 6.2 h, and from 62 to 99 h, respectively. The effective adsorption capacity of the modified board had increased by a multiple of two for formaldehyde and 1.8 for xylene. A mathematical model was developed and experimentally validated to evaluate the modification effect for more adsorbent-pollutant pairs. The results showed that the amplification of effective adsorption capacity was positively correlated with the Da/(K·De) parameter; this is the diffusion resistance ratio prior to and following the modification. A spectrogram of adsorbent–pollutant pairs was plotted to guide the modification. This simple macro-channel modification of the adsorption board may be used as an alternative design for adsorption applications in indoor air purification.

Enhanced Visible and Ultraviolet Light-Induced Gas-Phase Photocatalytic Activity of TiO2 Thin Films Modified by Increased Amount of Acetylacetone in Precursor Solution for Spray Pyrolysis

TiO2 thin films, modified by acetylacetone (AcacH) in solution, were deposited on glass substrate by ultrasonic spray pyrolysis and tested for photocatalytic activity in a multi-section continuous flow reactor by degradation of acetone and acetaldehyde under ultraviolet and visible light. The increase in molar ratio of AcacH in respect of titanium (IV) isopropoxide (TTIP) from 1:5 to 1:8 modified the electronic structure of the films, favoring enhanced photocatalytic activity. The photocatalytic activity was enhanced approximately twofold on the film with molar ratio 1:8 under both irradiations; the film completely oxidized 10 ppm of acetone and acetaldehyde. The photocatalytic efficacy of TiO2 films in oxidation of air pollutants was three times higher compared to the industrial glass Pilkington ActivTM. Moreover, all the synthesized films indicate antibacterial efficiency against E. coli of over 99% under ultraviolet. TiO2 film, with TTIP:AcacH molar ratio 1:8 having great possibility for its commercial use as a material for indoor air purification.

Simultaneous removal of VOCs and PM2.5 by metal-organic framework coated electret filter media

The electret filter media coated with highly porous metal-organic frameworks (MOFs) particles, named E-MOFilter, is newly developed and evaluated for its capacity for simultaneous removal of fine particulate matters (PM2.5) and volatile organic compounds (VOCs). Three different MOF particles, including MIL-125-NH2, UiO-66-NH2, and ZIF-67, were synthesized and systematically characterized. The produced MOF particles were suspended in ultrapure water and then a liquid filtration apparatus was used to deposit the MOF particles onto two electret media with different minimum efficiency reporting values (MERV 13 and 17) to form the E-MOFilters. Results showed that the MOF particles deposited in MERV 13 media more uniformly than that of MERV 17. In the PM filtration tests, results showed that the E-MOFilter gained only a few more pascals of air resistance compared with clean electret media. Besides, its PM removal efficiency was found to be close to that of clean electret media. This indicates that a uniform MOF particle deposition and negligible charge degradation from the current coating process were obtained. Further, the E-MOFilter with MIL-125-NH2 particle coating not only had a decent toluene removal efficiency (>80%) but also maintained its original PM2.5 holding capacity. This work may shed light on applying the novel E-MOFilter in the residential and commercial HVAC systems and indoor air purifiers to simultaneously and effectively remove PM2.5 and VOCs.

Energy Efficient Operation Cycle Determination Scheme of Fuzzy Based IHA in Air Purification IoT

Fine dust is a harmful particulate substance floating in the air and is divided into PM10 (which is 10 um in diameter or less) and PM2.5 (which is 2.5 um in diameter or less). Fine dust is a major cause of chronic respiratory diseases, which may occur naturally through forest fires or yellow dust, but it is mainly caused by combustion of fossil fuels such as oil and coal, or by automobile exhaust gases. When this type of bad outdoor fine dust flows into buildings, the indoor air becomes polluted, making it easier for workers or students who spend a lot of time indoors to be at risk for chronic respiratory diseases. To minimize this risk, recent research and development has focused on systems to purify indoor air by filtering fine dust. In this paper, we introduce a Wireless Sensor Networks (WSNs)-based Internet of Things (IoT) air purification system. In the WSNs-based IoT air purification system, it is important to maintain the integrity of the sensing data because the IoT air purifier operates based on the sensing data detected by sensor nodes. To defend the IoT air purifier against false report injection attacks, the existing fuzzy-based Interleaved Hop-by-Hop Authentication (IHA) detects false report injection attacks through Data Calibration. In addition to the existing fuzzy-based IHA sets, the security limit changes according to the network situation using fuzzy logic and adjusts the security and energy. However, the existing fuzzy-based IHA executes a fuzzy system every time it detects a normal event or false report injection attack, which requires additional message overhead and increases the transmission/reception energy, which increases the energy burden of the sensor nodes. To address this problem, we propose a method to control the operation cycle of the fuzzy system using the evaluation function. This proposed method has the advantage that the trade-off relationship between energy and security can be appropriately used to adjust the operation cycle and increase the lifetime of the network.

Synthesis of Pt-Loaded NiFe-LDH Nanosheets on Wood Veneer for Efficient Gaseous Formaldehyde Degradation.

Traditional methods of removing gaseous formaldehyde are often associated with high energy consumption and secondary pollution. In this study, a new wood veneer-based composite decorated with Pt-loaded NiFe-LDH nanosheets is successfully developed by a hydrothermal reaction and impregnation-chemical reduction. NiFe-LDH nanosheets as an adsorbent can capture formaldehyde molecules through their abundant hydroxyl groups. Pt nanoparticles as catalytic centers are evenly distributed on the surface of NiFe-LDH to excite the O atoms linked to NiFe-LDH and absorbed oxygen, which will further attack the absorbed formaldehyde molecules to generate CO2 and H2O. And the wood veneer not only increases the active area of the catalyst by endowing it with good dispersion but also provides convenient channels for reactants and products. In a simulated dark environment at room temperature, this synthetic wood veneer-based composite exhibits admirable catalytic activity, which can effectively degrade almost all gaseous formaldehyde with the initial concentration of 0.2 mg m-3 in 30 min and maintain a high catalytic activity of ≥97% after 10 cycles. This paper presents a feasible strategy for synthesizing an energy-efficient and ecofriendly wood veneer-based composite for efficient gaseous formaldehyde degradation at room temperature, which may play an important role in indoor air purification as a promising decorative material.

Morphology control of WO3 nanoplate film on W foil by oxalic acid for photocatalytic gaseous acetaldehyde degradation

WO3 film with reasonable morphology could be a promising photocatalytic material for indoor air purification. Herein, we constructed WO3 nanoplate film for photocatalytic degradation of gaseous acetaldehyde. The WO3 nanoplate film was prepared by nitric acid corrosion of W foil using oxalic acid for morphology regulation. SEM, XRD, and XPS evidenced that the monoclinic phase WO3 nanoplates grew on W foil. The oxalic acid anchored on the specific faces of the tungsten oxide hydrate facilitated for forming high quality larger and thinner WO3 nanoplates. UV–vis diffuse reflection spectra (DRS) manifested that the oxalic acid modulated WO3 nanoplate films possess smaller absorption edge and wider solar light absorption region. The oxalic acid contributed to obtain efficient WO3 nanoplate film photocatalyst for gaseous acetaldehyde decomposition under simulated solar light irradiation, which was response for the increased crystallinity and more surface reactive sites as well as the enhanced light absorption. The morphology modulation by oxalic acid will pave the way for synthesis of practical WO3 films in environment purification.

Oczyszczanie powietrza wewnętrznego w budynkach zrównoważonych

This paper concerns the issue of indoor air purification techniques in sustainable public buildings and the residential sector. One of the requirements of sustainable construction is to reduce the energy costs, minimize waste, improve the well-being of users and create green space. The most important certification systems for green (ecological) buildings such as LEED or BREEAM also include the assessment of the indoor environment in terms of the air quality, noise level, building acoustics and energy consumption. Traditional air treatment and purification systems require the use of numerous devices, air transport systems, which are energy-consuming. It is necessary to clean or replace the working elements periodically. The alternative is biophilic installations (green walls) based on the natural properties of plants for removing gaseous pollutants, particulate matter and even bioaerosols from the air. Plants improve humidity, regulate the carbon dioxide concentration, ionize the air and suppress noise. However, the processes of photocatalytic degradation of gaseous compounds are a very promising method of removing impurities, due to low costs, mild process conditions (temperature and pressure) and the possibility of complete mineralization of impurities.

Delocalization Effect Promoted the Indoor Air Purification via Directly Unlocking the Ring-Opening Pathway of Toluene

The ring-opening process was generally considered as the rate-determining step for aromatic volatile organic compound photocatalytic degradation. A sophisticated and intensive degradation pathway is critical to the poor removal efficiency and low mineralization. In the present contribution, we successfully tailored and identified the ring-opening pathway of toluene elimination by electron delocalization in a borocarbonitride photocatalyst. By means of modulation of the dopant coordination configuration and electron geometry in the catalyst, the lone electrons of carbon transform into delocalized counterparts, sequentially elevating the interaction between the toluene molecules and photocatalyst. The aromatic ring of toluene can be attacked directly in the effect of electron delocalization without engendering additional intermediate species, significantly facilitating the removal and mineralization of toluene. This unprecedented route-control strategy alters the aromatic-ring-based reaction behavior from toluene to CO2 and paves a way to purify the refractory pollutants from the top design.

Microchannel filter for air purification

AbstractIn this study, we propose a new design for a microchannel filter. The closed indoor environments with which we interact daily are sources of diseases for the respiratory system of human beings. Recommendations for the design of microchannel filters for indoor air purification are proposed, implementing low-cost microequipment technology (MET) for the manufacture of the elements that constitute a microfiltration system. For the microchannel filter production, we proposed to use MET, which is a miniaturization technology and can reduce manufacturing costs. The microchannel filter was 3.75 cm in radius with a thickness of 3 mm. It had a triangular profile and a helical trajectory. It was designed, manufactured, and tested for two profile dimensions. The main purpose was to reduce the pressure drop of the air flow through the filter. We described the air flow simulation for the microchannel filter using SolidWorks. A prototype microchannel filter was constructed, which underwent manufacturing tests. It is possible to clean the microchannel using water flow, which allows us to maintain the filtration quality within an optimum range of contaminant removal.

Research on Air Purification Wall Based on Heat Exchange Principle

With the acceleration of urban modernization, the use of prefabricated buildings on construction sites is increasing year by year. However, the following problems arise: the environmental quality of construction sites in our country is poor, the living comfort of prefabricated buildings is low, the recycling rate is low, and the indoor air is dirty, affecting the health and comfort of indoor personnel. Therefore, it is of great significance to complete the new wall for indoor air purification. Through the design of the three-layer interlayer, the heat exchange between the inside and outside air and the purification of the indoor air are realized, and a new type of movable plank house wall with low price and simple and ingenious structure is designed, which not only can improve the living comfort inside the plank house, but also can ensure the maximum embodiment of the energy-saving benefits of materials. The experimental results show that the indoor air quality of the air purification wall based on the heat exchange principle is improved by 21.6%, and the indoor temperature change in the air purification process can be effectively avoided.

Prototype of Eco-Friendly Indoor Air Purifier to Reduce Concentrations of CO2, SO2, and NO2

Prototype of Eco-Friendly Indoor Air Purifier to Reduce Concentrations of CO2, SO2, and NO2

A novel ternary Mica/TiO2/Fe2O3 composite pearlescent pigment for the photocatalytic degradation of acetaldehyde

A novel ternary mica/TiO2/Fe2O3 composite pearlescent pigment has been designed for the photocatalytic oxidation of gas-phase acetaldehyde in the application of indoor air purification. The mica/TiO2/Fe2O3-x (MTF-x, x = mFe2O3 : mTiO2 = 0.5–2: 100) composites were synthesized by a sol-gel assisted hydrothermal method. The MTF-1.5 composite shows optimal photocatalytic performance, which is 1.8 times photodegradation efficiency and 2.2 times CO2 mineralization efficiency higher than those of pure TiO2. The enhanced photocatalytic performance of MTF-x (x = 0.5–2) composites could be associated with enhanced reflectivity of mica, which eventually improved the light absorption properties. Also, the presence of TiO2/Fe2O3 heterostructure facilitated charge separation in the MTF ternary composite. Besides, superoxide radical was proven as the decisive active species for the degradation of gaseous acetaldehyde. This work provides a systematic approach to develop a potential multi-functional pearlescent pigment to purify indoor air.

Purification of Indoor Air from Pollutants by Areca Palm (Chrysalidocarpus lutescens L.) Treated with some Non-Enzymatic Antioxidants

Indoor plants play an important role in purification the indoor air pollutants. Therefore, the main objective of this investigation was to increase the resistance of areca palm plants to the excessive concentrations of air gaseous pollutants. The present study was carried out in plastic chambers (80cm length×80cm width×100cm height) for exposing plants to formaldehyde or ammonia gasses after spraying with non-enzymatic antioxidants (glutathione and bilirubin at 300mg L-1 and 600mg L-1). Plants exposed to ammonia were highest in the number of dead leaves and leave injury percentage comparing with the plants exposed to formaldehyde. Plants treated with glutathione at 600 mg L-1 or bilirubin at 300mg L-1 before exposure to formaldehyde gas were not injured leaves, as well as, increased in dry weight and chlorophyll concentration compared with the plants exposed to formaldehyde gas without spraying with antioxidants. Spraying plants with bilirubin at 300mg L-1 before exposure to formaldehyde were increased in total carotenoids as well as increased guaiacol peroxidase (GOPX) and catalase (CAT) activities under formaldehyde whereas it increased the activeties of ascorbate peroxidase (APX) and polyphenol oxidase (PPO) under ammonia. Also, plants treated with bilirubin or glutathione increased in stomata density and pore length under formaldehyde gas. In conclusion, spraying areca plants with bilirubin at 300 mg L-1 enhanced the plant resistance to the formaldehyde and ammonia air pollutants followed by glutathione treatments. Areca palm plants were higher sensitivity to ammonia gas than with formaldehyde gas.

Effects of the Use of Air Purifier on Indoor Environment and Respiratory System among Healthy Adults.

Air purifiers have become popular among ordinary families. However, it remains controversial whether indoor air purification improves the respiratory health of healthy adults. A randomized crossover intervention study was conducted with 32 healthy individuals. The subjects were categorized into two groups. One group continuously used true air purifiers, and the other followed with sham air purifiers for 4 weeks. Following this first intervention, all the subjects underwent a 4-week washout period and continued with the second 4-week intervention with the alternate air purifiers. We collected fine particulate matter (PM) ≤ 2.5 µm in aerodynamic diameter (PM2.5), coarse particulate matter between 2.5 and 10 µm in aerodynamic diameter (PM10–2.5) and ozone (O3). The subjects’ pulmonary function and fractional exhaled nitric oxide (FeNO) were measured during the study period. The indoor PM2.5 concentrations decreased by 11% with the true air purifiers compared to those with sham air purifiers. However, this decrease was not significant (p = 0.08). The air purification did not significantly improve the pulmonary function of the study subjects. In contrast, an increase in the indoor PM10–2.5 and O3 concentration led to a significant decrease in the forced expiratory volume in one second (FEV1.0)/forced vital capacity (FVC) and maximal mid-expiratory flow (MMEF), respectively. In conclusion, air purification slightly improved the indoor PM2.5 concentrations in ordinary homes but had no demonstrable impact on improving health.

Fuzzy based Dynamic Security Parameters Determination Method to Improve Energy Efficiency

Fine dust is a harmful substance that floats in the atmosphere. It is not filtered well in the bronchus and causes health problems when it accumulates in the body. Fine dust that is present in the air outside can flow into buildings through windows and other openings, adversely affecting indoor air quality. It has negative health effects on people who live indoors. As attention to problems associated with fine dust gradually rises, the importance of continuously managing the quality of indoor air through air purification rises. Therefore, recently, research and development into systems to periodically purify indoor air are being carried out. This paper introduces an air purification system, a Wireless Sensor Networks (WSNs)-based Internet of Things (IoT) air purification system. In the WSNs-based IoT air purification system, the IoT air purifier is controlled based on event information that the WSNs senses, so it is important to maintain the security of the event information. To this end, a WSNs security protocol, Interleaved Hop by hop Authentication (IHA), is used in this system. IHA is a security protocol in which sensor nodes and a Base Station (BS) detect and drop false reports if the number of compromised sensor nodes does not exceed a security threshold. That is, because the false report injection attack that the number of compromised sensor nodes exceeds security threshold can’t defend by IHA, it is detected and defended through Data Calibration. However, considerable energy of the sensor nodes is unnecessarily consumed in the process of forwarding false reports. Thus, this paper proposes a method of decreasing and increasing security thresholds dynamically according to the network situation using fuzzy logic. This proposed scheme has the advantages of improvements in both the overall energy efficiency and network lifetime in WSNs.