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Objective: Previous studies have reported that ambient air pollutants such as PM2.5 can increase the risk of adverse birth outcomes. The objective of this study was to ascertain whether air purifier usage during pregnancy is associated with a lower risk of adverse birth outcomes in a large Japanese birth cohort. Methods: We conducted a prospective cohort analysis using data from the Japan Environment and Children's Study. Use of air purifiers during pregnancy was assessed using a self-administered questionnaire. Primary outcomes were the prevalence of preterm birth (PTB), small for gestational age (SGA), and low birth weight (LBW). Logistic regression analysis was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: The prevalence of outcomes was 4.5% for PTB, 7.4% for SGA, and 8.1% for LBW. The crude model analysis revealed that PTB, SGA, and LBW showed lower ORs in the group that used an air purifier, although the association disappeared in the adjusted model except for SGA (OR: 0.94; 95% CI: 0.89, 1.00, p = 0.048) and LBW (OR: 0.93; 95% CI: 0.88, 0.98, p = 0.003). Subgroup analysis stratified by infant sex revealed that the lower OR for LBW was observed only in male infants. Conclusions: Our results suggest that avoiding maternal air pollution exposure during pregnancy may be useful in preventing adverse birth outcomes. These findings provide evidence supporting the development of protective measures against air pollutants in the gestational period by relevant health agencies. [ABSTRACT FROM AUTHOR]

Conventional air purifiers are low effective in inactivating airborne bacteria and may cause secondary contamination by releasing endotoxins. In this study, a novel air purifier was developed and used in a static chamber, which used slightly acidic electrolysed water (SAEW) solutions as the circulating disinfectant spray medium that automatically renewed every 30 min. During the 30-minute operation, the air and solution samples were collected to measure the bacteria and endotoxin concentration by using a culturable-based method and a limulus amoebocyte lysate assay kit, respectively. The pH and endotoxin of the circulating solution were gradually increased, and the available chlorine concentration (ACC, from 87 to 50 mg/L) was decreased. Although airborne bacteria were reduced significantly, the levels of airborne endotoxins at the inlet and outlet of the purifier remained constant. Moreover, a validation experiment revealed that SAEW, with ACC of 20, 60 and 100 mg/L, cannot inactivate standard endotoxin solutions. In the experimental chamber, the airborne bacteria level (1142 CFU/m3) was significantly lower compared to the control chamber (3325 CFU/m3), with no significant difference in airborne endotoxin levels between the chambers. Our results showed that the SAEW spray air purifier could effectively remove airborne bacteria without increasing airborne endotoxin levels within a 30-minute operational period. [ABSTRACT FROM AUTHOR]

Air pollution is currently the most significant environmental factor posing a threat to the health and lives of European residents. It is a key cause of poor health, particularly respiratory and cardiovascular diseases. The primary aim of the study was to numerically determine the impact of the air purifier model's geometry on the distribution of air within a room and to conduct experimental tests on the filtration efficiency and preliminary antibacterial activity of filtration composites. The scope of the work included designing an air purifier model in the form of a pendant lamp and performing computer simulations in Ansys software to identify the optimal shape. The experimental research focused on developing filtration composites consisting of nonwoven fabric with an active hydrosol layer, meltblown nonwovens and a carbon filter. The study results showed that the SMMS composite with 50% thyme and carbon nonwoven exhibited the highest filtration efficiency for both small and large particles. [ABSTRACT FROM AUTHOR]

Chinese urban residential buildings face serious indoor air quality problems. Air purification systems (e.g., air purifiers, fresh air systems) that supply fresh air or purify indoor air are widely used in residential buildings to improve indoor air quality. Considering the challenges of energy conservation and emission reduction, it is urgent to guide residents on choosing appropriate air purification systems. The key problem is how to identify the best air purification system with the lowest energy consumption or operating cost. Comparisons of air purification systems have rarely been conducted on the premise that they should deliver air such that the main indoor pollutant concentrations all meet air quality standards. Also ignored in comparisons are the increased filtration resistance caused by dust accumulation on the filter and the cost of filter replacement. In this study, we propose a method to compare residential air purification systems based on energy consumption and total cost, and we provide methods to select air purification systems in China's different climatic regions. We used a standard two-person bedroom as the example, and determined the most suitable (minimum cost or energy consumption) air purification systems for the capital cities of the provinces in Chinese mainland. [ABSTRACT FROM AUTHOR]

High-efficiency particulate air (HEPA) filter purifiers are a recommended method for eliminating respiratory airborne droplets. In this study, the movement of airborne droplets exhaled by occupants in an unventilated, two-bed dormitory room with an air purifier was simulated using computational fluid dynamics. The air was modeled using an Eulerian scheme while the droplets were modeled using a Lagrangian method. The airborne droplet number, the rate at which droplets are removed, and the rate at which droplets accumulate were calculated. A larger HEPA flow rate increased the droplet removal efficiency, with most of the droplets settling on boundary surfaces. Of particular note, the air purifier location within the room had a significant impact on reducing the droplet exchange between two occupants and improving the droplet elimination efficiency. [ABSTRACT FROM AUTHOR]

The aims of this study encompass the characterization of process parameters and the antimicrobial potential during operation of a novel non-thermal plasma (NTP) source in a duct system containing a particulate matter (PM) filter thus mimicking the interior of an air purifier. Simulating conditions of a long-term operation scenario, in which bacterial aerosols in indoor environments accumulate on PM filters, the filter surfaces were artificially inoculated with Escherichia coli (E. coli) and exposed to an air stream enriched with reactive species. Electrical power consumption, key plasma parameters, volume flow and air flow velocity, reactive gas species concentrations as well as inactivation rates of E. coli were assessed. The NTP operated at a gas temperature close to ambient air temperature and featured a mean electron energy of 9.4 eV and an electron density of 1∙1019 m−3. Ozone was found to be the dominating reactive gas species with concentrations of approx. 10 ppm in close vicinity to the PM filters. An inactivation rate of 99.96 % could be observed after exposure of the PM filters to the gas stream for 15 min. This inactivation efficiency appears very competitive in combating realistic bacterial aerosol concentrations in indoor environments. [ABSTRACT FROM AUTHOR]

As concerns about indoor air quality increase, air purifiers and fresh air systems are increasingly being used in conjunction with air conditioners in office buildings. To study the synergistic effects of multisystem joint operation on indoor air quality, this study used a combination of experimental and simulation methods to study the indoor particulate matter with a diameter of less than 2.5 µm (PM2.5) and carbon dioxide (CO2) concentrations under different operation conditions. The purification time and the PM2.5 concentration distribution under different conditions were compared with the condition in which the purifier was used alone. The results showed that the purification time required for the condition that the air conditioner runs together with the purifier was shortened by 15.2%. When the fresh air system is running together with the purifier, the purification time can be reduced by 30.4%. It was reduced by 32.6% when the three systems were operating at the same time. The PM2.5 concentration distribution under the joint operating condition was much more even than that under the condition in which the purifier was running alone. To analyze the impact on the CO2 distribution, the CO2 distributions under different joint operations were compared. The results show that the fresh air system can effectively dilute CO2 below 1000 ppm in 30 min. The air conditioner and purifier could help to mix the indoor air to provide a much more uniform indoor CO2 distribution. [ABSTRACT FROM AUTHOR]

IntroductionMany school buildings have inadequate ventilation, rudimentary if any air filtration, and aging and poorly maintained mechanical systems, all of which can lead to poor indoor air quality (IAQ). These issues are especially acute in environmental justice (EJ) communities where schools are located in polluted areas. This community-based participatory research examines how IAQ in naturally ventilated school buildings is affected by the use of air purifiers, air change rates, outdoor pollution levels, and teacher and staff behavior.MethodsIAQ assessments were performed at two schools in Detroit, Michigan, which included building walk-through inspections and continuous indoor and outdoor measurements of black carbon (BC), particulate matter (PM10 and PM2.5), carbon dioxide (CO2), air change rates (ACRs), temperature, humidity, and sound pressure levels. Air purifiers with usage monitors were then installed, and the IAQ assessments were repeated. Teachers were surveyed before and after purifier deployment.ResultsAt baseline, classrooms had low ACRs (0.58–1.38 h−1), moderate PM2.5 levels (2.8–8.9 μg/m3), highly variable PM10 concentrations (4.7–37.5 μg/m3), and elevated BC levels (0.3–0.7 μg/m3), reflecting emissions from local traffic, industry and other sources. The installation and use of purifiers reduced pollutant levels and the overall performance matched the predictions of a single compartment model. However, daily reductions varied widely among classrooms, reflecting differences in teacher behavior regarding the frequency of opening windows and the operation of purifiers, including differences in purifier fan speed settings and whether purifiers were used at night. Survey responses indicated that many teachers were aware of IAQ problems. The higher rates reported for health symptoms and dissatisfaction at one school may have lowered the teachers’ tolerance to noise and reduced purifier use.DiscussionThe study helps explain the variation reported in prior studies using purifiers, and it reinforces the need to monitor IAQ and purifier use, use enhanced filtration and increase ventilation, and engage with teachers and school staff to support and maintain IAQ programs in schools.

In indoor spaces without mechanical ventilation systems, a common approach involves using a ceiling-mounted 4-way fan coil unit (4WFCU) to regulate indoor temperature and placing floor-level air purifiers (APs) to remove indoor pollutants. This study introduces a differentiated displacement ventilation system (DVS) that connects multiple APs to the 4WFCU using ductwork. The age of air was compared between the case where the newly designed DVS was implemented and the reference case where 4WFCU and APs operated independently. When there were no obstacles in the office central area, the reference system exhibited a lower age of air. Conversely, when obstacles such as desks and partitions were present in the central area, the proposed DVS was found to improve indoor air quality. The DVS resulted in minimal interference among pathlines of the air discharged from multiple floor-level APs and their efficient suction through the ceiling-mounted 4WFCU and diffusers, significantly reducing stagnant air zones, while pathlines of the air discharged from the 4WFCU and APs interfered significantly when they operated independently, leading to larger stagnant areas in the air distribution. Therefore, modifying office spaces with ceiling-mounted 4WFCUs using the proposed DVS is anticipated to substantially enhance indoor air quality through a straightforward installation process. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of ventilation rate and air supply angle of an air purifier using computational fluid dynamics to determine the dispersion of airborne COVID virus exhaled by an infected person. The risk of infection for an occupant was determined based on the virus concentration in the active area and accumulated particle dose within the breathing zone by varying the ventilation parameters. The air purifier was found to provide a local dilution and would block the development of an expiratory jet for a short time to reduce transmission risk. Compared to the case without an air purifier, the maximum reductions were 94.27% in the accumulated dose and 53.2% in the particle count concentration. In the breathing area, the larger air supply angle (90° > 60° > 30°) is better when the ventilation rate was 27.0 m3/h and 40.5 m3/h. Otherwise, 60° air supply angle is preferable where the ventilation rate was 54.0 m3/h. Assessing the results with the grey relational analysis revealed that the relational degree for particle count concentration was greater by varying the ventilation rate than by varying the air supply angle. However, the relational degree according to the accumulated dose was greater by varying the air supply angle than by increasing the ventilation rate. These findings may provide an important control strategy to effectively mitigate the risk of infection in a confined room by using an air purifier. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated the effectiveness of photocatalytic oxidation (PCO) and air filtration technology for removing indoor air pollutants and improving the health of patients with asthma. Methods: A double-blind crossover study was conducted. In total, 58 patients with asthma residing in a heavily industrialized area were recruited. The patients were randomly assigned to two groups: a PCO group and a PCO+filter group. The PCO+filter group underwent an intervention that consisted of a 2-week period using a PCO and a filter, a 2-week washout period, and a 2-week period using only a PCO. The PCO group followed the same sequence, with interventions reversed. During the intervention period, measurements were taken to assess the removal of indoor particulate matter (PM1, PM2.5, PM4, PM10, TSP, and UFPs), gaseous pollutants (CO, SO2, NO2, CO2, and TVOC), and their effect on health outcomes, including lung function, blood pressure, FeNO levels, ACT score, and symptoms. Results: Significant reductions in indoor gaseous pollutants, such as SO2 and TVOC, were observed in the PCO group. Significant reductions in PM, CO, NO2, and TVOC were observed in the PCO+filter group. Improvements in lung function were observed after only 7 days, and significant reductions in blood pressure were observed after 13 days. Both groups reported improvements in symptoms. Conclusions: Individuals living in highly polluted industrial areas can mitigate the adverse health effects of air pollution by adopting air purifier technology. [ABSTRACT FROM AUTHOR]

Airborne particles containing pathogens such as bacteria (e.g., M. tuberculosis) or virions (e.g., influenza or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)) can cause infections. It has been speculated that the outflow from indoor air purifiers with a directional outlet could entrain and spread pathogen-containing aerosol particles. To date, only the case of indoor air purifiers with a directional outflow has been considered, and here we investigate an indoor air purifier with a circumferential outflow diffuser—an alternative design solution that is already commercially available. We measured the airflow velocity at two different angles to the surface of the circumferential outflow diffuser and two blower speeds. We visualized in scattered light the deflection of a vertical mist spray cone from a sneeze-simulating nebulizer parallel to the side of the air purifier. We found a significant difference in airflow velocities for different angles to the circumferential outflow diffuser: 0.01–0.02 m/s for 0° vs. 0.01–0.65 m/s for 45° at 1 m distance. We observed no significant deflection of the sneeze-simulating spray cone at the minimum blower speed and a 5 cm deflection at the maximum speed. The deflection of the sneeze-simulating spray mist particles by the tested indoor air purifier with the circumferential outflow, under the experimental conditions, is low relative to the recommended safer distances between people in indoor spaces. We conclude that indoor air purifiers with circumferential outflow diffusers have a lower potential to spread infectious aerosols in indoor spaces compared to devices with unidirectional outflow. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of portable and large filter-based air cleaners (HEPA filters), which became popular indoors during the COVID-19 pandemic, and their suitability for classrooms (here 186 m3). The decay rates of the particle number concentration (PNC) were measured simultaneously at up to four positions in the room. It was found that the different air outlet configurations of the units have an effect on the actual PNC removal in the room when operated at the same volume flow rates. This effect of the airflow efficiency of the air cleaners (AP) in a classroom is quantified with an introduced Air Cleaning Efficiency Factor in this study to identify beneficial airflows. In this context, the effect of filter loading in long-term operation on the cleaning effect is also investigated. The emitted sound pressure levels of the APs are given special attention as this is a critical factor for use in schools, as well as power consumption. A total of six different devices were tested—two portable APs and four large APs. In order to achieve the necessary volume flow rates, three or four of the portable units were used simultaneously in one room, while only one of the large units was used per room. When used at the same air circulation rates in the room, the portable APs exhibit higher sound pressure levels compared to the large APs. At air circulation rates of 4–5 h−1, the portable APs exceeded a value of 45 dB(A). Two of the four large units reach sound pressure levels below 40 dB(A) at air circulation rates of 4–5 h−1, whereby both large units, which are positioned on the rear wall, realize a homogeneous dilution of the room air. This is achieved by an air outlet directed horizontally at a height above 2 m or diagonally towards the ceiling, which points into the room and partly to the sides. On the other hand, an air outlet directed exclusively to the sides or horizontally into the room at floor level to all sides achieves lower particle decay rates. To investigate the influence of the filter loading, three large APs were operated in a school for a period of one year (190 days with 8 h each). For the three APs, long-term operation leads to different changes in PNC reduction efficiency, ranging from −3% to −34%. It is found that not only the size of the prefilter and main filter has a significant influence, but also whether there is a prefilter bypass that negatively affects the loading level of the main filter. At the same time, it was shown that one type of AP, measuring the pressure drop across the filters and readjusting the fan, kept the circulation rate almost constant (up to −3%) over a year. [ABSTRACT FROM AUTHOR]

Summary: Insufficient quantity and quality of sleep is a public health concern that can be addressed by interventions for improving sleep outcomes. Environmental factors such as poor air quality are a potential target for intervention, particularly in light of associations between air pollution and worse sleep. The aim of this pilot study was to investigate the effects of using an air purifier on sleep outcomes and mood in 30 healthy adults. There were two conditions: (i) air purifier with a high‐efficiency particulate air filter; (ii) air purifier with a placebo filter. Participants undertook both conditions, each over 2 weeks with a 2‐week washout, following a counterbalanced, double‐blind design. Daily sleep outcomes were measured with actigraphy watches and sleep diaries, whilst daily mood was assessed with the Positive and Negative Affect Schedule. The Insomnia Severity Index, the Pittsburgh Sleep Quality Index, and symptoms of anxiety and depression were measured pre‐ and post‐. The purifier filter was associated with increased total sleep time for an average of 12 min per night, and increased total time in bed for an average of 19 min per night relative to the placebo. There were several sleep and mood outcomes for which no changes were observed, and time awake after sleep onset was higher for the purifier filter. Air quality was better during the high‐efficiency particulate air filter condition. These findings offer positive indications that environmental interventions that improve air quality can have benefits for sleep outcomes in healthy populations who are not exhibiting clinical sleep disturbances. [ABSTRACT FROM AUTHOR]

Physical adsorption of volatile organic compounds （VOCs） is a rapid and versatile purification method, which has been widely used in indoor air purifiers. However, due to the limited adsorption amount and the varying of environmental temperature, it often causes secondary pollution to indoor air and seriously threatens people's health during using. The way to avoid secondary pollution through frequent replacement of consumables will not only cause economic losses to consumers, but also bring serious burden to the environment and downstream recycling industry. Therefore, we propose a new VOCs purification method based on Mn-mullite catalyst （YMn2O5, YMO）+ozone. The results show that C3H6 is completely degraded into carbon dioxide and water at 18℃ and 120000 mL/（g·h). Incense with main components including propylene, polycyclic aromatic hydrocarbons and aliphatic hydrocarbons is used as VOCs source. Under different initial concentrations and relative humidity conditions, the homemade air purifier can rapidly degrade VOCs at 18 ℃, and its clean air delivery rate reaches 75 m³ /h. As VOCs initial concentration increases, the time for completing degradation also increases. Besides, the relative humidity changing will also affect the degradation rate of VOCs. When the relative humidity is 40%, the homemade air purifier has the fastest degradation rate. The YMO+O3 route can effectively degrade VOCs without secondary pollution at room temperature with large humidity variation. Because of the unlimited theoretical lifetime and excellent performance of the catalyst, this technological route is expected to be popular in the next generation of air purifier. [ABSTRACT FROM AUTHOR]

Air pollution is now a global problem due to its increased devastating effect on the normal lifestyle of every human being as well as animal. With the growing population, urbanization and industrialization have affected the environment severely by adding very fine particles, unwanted gases, and elements to the air. The major sources of outdoor air pollution are open-air waste burning, emission of unwanted gases, and aerosols from vehicles and industries. Inhalation of these toxic gases and particles is the prime source of lung-related fatal diseases. The increase in the percentage of death due to air pollution is an alarming circumstance for the entire world. The countries like India, which are at the developing stage, are suffering more from the consequences of air pollution. These countries have failed to make adjustments between the full filling of the livelihood need of the growing population and the healthy environment to live in. Therefore, it leads to the high necessity of developing low-cost and effective air cleaning technology to offer people healthy living. The present work describes the design optimization process of an outdoor air purifier based on Computational Fluid Dynamics analysis. Initially the internal aerodynamics of air purifier installed at CSIR-CMERI Colony, Durgapur, India is simulated and results ware verified with experimental data. Hereafter, external aerodynamics simulations are performed in order to optimize the gap between inlet and exit. Based on this study, few design modifications are suggested and all these modifications can also be optimized based on the pressure losses and the dissipation losses inside the purifier. [ABSTRACT FROM AUTHOR]

As concerns about indoor air quality increase, air purifiers and fresh air systems are increasingly being used in conjunction with air conditioners in office buildings. To study the synergistic effects of multisystem joint operation on indoor air quality, this study used a combination of experimental and simulation methods to study the indoor particulate matter with a diameter of less than 2.5 µm (PM2.5) and carbon dioxide (CO2) concentrations under different operation conditions. The purification time and the PM2.5 concentration distribution under different conditions were compared with the condition in which the purifier was used alone. The results showed that the purification time required for the condition that the air conditioner runs together with the purifier was shortened by 15.2%. When the fresh air system is running together with the purifier, the purification time can be reduced by 30.4%. It was reduced by 32.6% when the three systems were operating at the same time. The PM2.5 concentration distribution under the joint operating condition was much more even than that under the condition in which the purifier was running alone. To analyze the impact on the CO2 distribution, the CO2 distributions under different joint operations were compared. The results show that the fresh air system can effectively dilute CO2 below 1000 ppm in 30 min. The air conditioner and purifier could help to mix the indoor air to provide a much more uniform indoor CO2 distribution.

Existing indoor closed ultraviolet-C (UVC) air purifiers (UVC in a box) have faced technological challenges during the COVID-19 breakout, owing to demands of low energy consumption, high flow rates, and high kill rates at the same time. A new conceptual design of a novel UVC-LED (light-emitting diode) air purifier for a low-cost solution to mitigate airborne diseases is proposed. The concept focuses on performance and robustness. It contains a dust-filter assembly, an innovative UVC chamber, and a fan. The low-cost dust filter aims to suppress dust accumulation in the UVC chamber to ensure durability and is conceptually shown to be easily replaced while mitigating any possible contamination. The chamber includes novel turbulence-generating grids and a novel LED arrangement. The turbulent generator promotes air mixing, while the LEDs inactivate the pathogens at a high flow rate and sufficient kill rate. The conceptual design is portable and can fit into ventilation ducts. Computational fluid dynamics and UVC ray methods were used for analysis. The design produces a kill rate above 97% for COVID and tuberculosis and above 92% for influenza A at a flow rate of 100 L/s and power consumption of less than 300 W. An analysis of the dust-filter performance yields the irradiation and flow fields. [ABSTRACT FROM AUTHOR]

This study comprehensively investigated the efficacy of five distinct air purifiers in the removal of both particulate matter and gaseous pollutants. The analysis was conducted within a consistent test environment, employing a standardized benchmark to ensure accurate and comparable results. A rigorous methodology was devised to evaluate the efficiency of each air purification mechanism. The experimental setup involved placing the air purifiers inside a controlled test chamber, carefully designed to replicate typical indoor conditions. The focus of the analysis was on the removal efficiency of PM2.5, and the evaluation utilized the Clean Air Delivery Rate (CADR) values, measured in cubic feet per minute (ft³/min or CFM). Importantly, the study maintained uniform specifications, including unit filter area and unit electrostatic volume, to facilitate a fair and meaningful comparison of the removal efficiency for each purification mechanism. The CADR values served as a quantitative metric to assess the air purifiers’ effectiveness in removing PM2.5 particles. This standardized approach allowed for a direct comparison of their performance under identical conditions. By considering unit filter area and electrostatic volume, the study aimed to provide insights into the relative merits of each mechanism, enabling consumers to make informed decisions based on the specific removal capabilities of the air purifiers. In summary, the research established a robust methodology for evaluating air purifier performance, facilitating a thorough analysis of their effectiveness in removing particulate matter and gaseous pollutants within a controlled environment. The use of CADR values and standardized specifications ensures a reliable basis for comparing the efficiency of different air purification mechanisms.

Electronic air cleaning (EAC) technologies have garnered significant attention for use in buildings. Many EAC technologies rely on the addition of reactive constituents to indoor air to react with gas-phase compounds, enhance particle deposition, and/or inactivate microorganisms. However, limited data are available on the efficacy of many EAC technologies and their potential to form chemical byproducts during operation. Here we experimentally evaluate the indoor air quality impacts, specifically targeting particles and gases but not microbial constituents, of a commercially available additive oxidizing EAC that generates positive and negative ions and hydrogen peroxide (H2O2). Tests were conducted in a large unoccupied test chamber in Chicago, IL and an unoccupied laboratory in Portland, OR under a combination of natural conditions (i.e., without pollutant injection) and perturbation conditions (i.e., with pollutant injection and decay). A combination of integrated and time-resolved measurements was used across both test locations. Chamber tests at lower airflow rates demonstrated that operation of the EAC: (i) had no discernible impact on particle concentrations or particle loss rates, with estimated clean air delivery rates (CADRs) for various particle measures less than ±10 m3/h, (ii) was associated with apparent decreases in some volatile organic compounds (VOCs) and increases in other VOCs and aldehydes, especially acetaldehyde, although a combination of high propagated uncertainty, limitations in test methods (e.g., lack of replicates), and variability between repeated tests limit what quantitative conclusions can be drawn regarding gas-phase organics; (iii) did generate H2O2, assessed using a crude measure, and (iv) did not generate ozone (O3). Laboratory tests at higher airflow rates, which involved injection and decay of particles and a single VOC (limonene), both simultaneously and separately, demonstrated that: (i) pollutant loss rates for both particles and limonene were slightly lower with the EAC on compared to off, yielding slightly negative pollutant removal efficiencies (albeit largely within propagated uncertainty) and (ii) there was a change in observed concentrations of one potential limonene degradation product, m/z 59 (putatively identified as acetone), with steady-state levels increasing from 10 ppb (air cleaner off) to 15 ppb (air cleaner on). No increases or decreases beyond measurement uncertainty were observed for other analyzed gaseous limonene degradation products. Overall, both chamber and laboratory tests demonstrated negligible effectiveness of this device at the test conditions described herein for removing particles and mixed results for VOCs, including decreases in some VOCs, no discernible differences in other VOCs, and apparent increases in other compounds, especially lower molecular weight aldehydes including acetaldehyde.

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This study aimed to develop and implement a fuzzy logic controlled-intelligent air purifier/humidifier. The concepts of passive purification and evaporative humidification were used to build this device, and engineering ideas and theories were used to guide the development of electrical and mechanical systems. Additionally, a fuzzy logic controller was designed, built and integrated into the air purifier/humidifier device to help with its operation. It does this by analysing input signals from all the sensors (dust, volatile organic compound gas, humidity and water level) and activating the actuators (suction and blow fan). On the Arduino IDE, a C/C++ programming code was developed and uploaded onto the Arduino Uno R3 board, which houses the ATmega328P microcontroller processor. In estimating the clean air delivery rate (CADR), noise level and moisture delivery rate, the performance of the developed air purifier/humidifier was assessed. Additionally, the electrical systems' power consumption and the fuzzy logic controller's ease of use were each assessed. In light of the room capacity taken into consideration, the findings obtained demonstrated that the proposed air purifier/humidifier device satisfies the minimum standard requirement of a CADR of 140m3/hr. The outcome also revealed that the designed device's noise level is lower than the typical threshold for an air purifier, which is less than 40 db. Additionally, after 68 minutes, the device raised the humidity level in a controlled area from 21% to 40%. [ABSTRACT FROM AUTHOR]

Prevention of PM2.5 is attracting increasing attention all over the world as PM2.5 can cause and exacerbate respiratory diseases. Compared with conventional natural ventilation and mechanical ventilation, air purifiers with particular filters are more efficient in the control of indoor PM2.5. Currently, there are limited studies on the operations of portable indoor air purifiers. To improve the efficiency of an air purifier in control of PM2.5, an optimal operational strategy is needed. This paper proposes a framework for the optimization of operations of air purifiers for control of indoor PM2.5 based on building information modeling (BIM) and computational fluid dynamics (CFD). A case study is conducted to validate the proposed optimization framework and the results are discussed. It can be shown from the results that the best location of the air purifier can increase efficiency by up to 33% compared with other locations. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the current coronavirus disease 2019 (COVID-19) pandemic, is evolving. Thus, the risk of airborne transmission in confined spaces may be higher, and corresponding precautions should be re-appraised. Here, we obtained the quantum generation rate (q) value of three SARS-CoV-2 variants (Alpha, Delta, and Omicron) for the Wells-Riley equation with a reproductive number-based fitted approach and estimated the association between the infection probability and ventilation rates. The q value was 89–165 h−1 for Alpha variant, 312–935 h−1 for Delta variant, and 725–2,345 h−1 for Omicron variant. The ventilation rates increased to ensure an infection probability of less than 1%, and were 8,000–14,000 m3 h−1, 26,000–80,000 m3 h−1, and 64,000–250,000 m3 h−1 per infector for the Alpha, Delta, and Omicron variants, respectively. If the infector and susceptible person wore N95 masks, the required ventilation rates decreased to about 1/100 of the values required without masks, which can be achieved in most typical scenarios. An air purifier was ineffective for reducing transmission when used in scenarios without masks. Preventing prolonged exposure time in confined spaces remains critical in reducing the risk of airborne transmission for highly contagious SARS-CoV-2 variants. [ABSTRACT FROM AUTHOR]

Background: A locally installed air purifier unit (Novaerus Protect 800) has been shown to reduce the air bioburden in an intensive care unit and the incidence of healthcare-associated infections.Aim: To explore whether this type of air purifying unit could reduce bacterial concentrations in the air of an operating room (OR) during orthopaedic surgery, thereby reducing the risk of surgical site infections.Methods: In this prospective experimental study, undertaken in 2018, three air purifying units were installed in an OR in a Swedish hospital in 2018. The air was actively sampled during 11 operations by a slit-to-slit agar impactor with the air purifying units either switched on or switched off. Air movements were visualized with the aid of smoke in mock-up studies.Findings: No significant difference in bacterial concentrations in air was found between the two conditions (air purifying units switched off or on) (P=0.54). Air movements around and above the surgical wound were disordered and resembled those of dilution mixing air.Conclusion: The three air purifying units installed in the OR did not reduce the airborne bacterial levels in the critical zone during orthopaedic surgery. [ABSTRACT FROM AUTHOR]

BackgroundExposure to PM2.5 will accelerate the progression of cardiovascular diseases. Air purifier can reduce the PM2.5 exposure and theoretically alleviate the influence of PM2.5 on patients with stable coronary artery disease (SCAD). However, few studies of the protective effect showed significant results because the interferent effects of routine medication had not been taken into account. In order to explore the actual effect on patients with SCAD, we conducted a randomized single-blind crossover air purifier intervention trial.MethodLevels of PM2.5 exposure during intervention and cardiovascular indicators (inflammation, coagulation, plaque stability, and blood lipids) after intervention were detected, meanwhile the information of drug use was obtained by questionnaire. The kinds of drug used by more than 20% of the subjects were sorted out. And the influence of these drugs on cardiovascular indicators was summarized through literature review. Based on that, the drug use was included as a variable in linear mixed effects models that used to analyze the associations between PM2.5 exposure reduction by air purifier and cardiovascular indicators.ResultsThe result revealed that the interpretation contribution rate of drug use was more than that of PM2.5 exposure. The level of C-reactive protein significantly decreased by 20.93% (95%CI: 6.56%, 33.10%), 23.44% (95%CI: 2.77%, 39.39%) and 24.11% (95%CI: 4.21%, 39.69%) on lag1, lag01 and lag02 respectively, while the level of high-density lipoprotein cholesterol significantly increased by 5.10% (95%CI: 0.69%, 9.05%), 3.71% (95%CI: 0.92%, 6.60%) and 6.48% (95%CI: 2.58%, 10.24%) respectively on lag0, lag1 and lag01 associated with an interquartile range decrease of 22.51 μg/m3 in PM2.5 exposure.ConclusionThe study shows positive effects of air purifier on SCAD, and also provides methodological reference for future related research.

Indoor PM2.5 in apartments must be effectively managed to minimize adverse impacts on human health. Cooking is the one of the main PM2.5 sources in apartments, and indoor air quality (IAQ) management methods (natural ventilation, mechanical ventilations, range hoods, and air purifiers) are typically used to reduce PM2.5 generated during cooking. For effective control of indoor PM2.5, prediction of PM2.5 reduction for various IAQ management methods is necessary. This study carefully predicted indoor PM2.5 concentrations in an apartment when IAQ management methods were applied separately and/or in combination during cooking. The infiltration and exfiltration were verified by comparing the experimental results of CO2 concentration with those predicted with or without mechanical ventilation. The deposition rate for PM2.5 generated by cooking was also derived by comparing the experimental PM2.5 changes with the predicted values for PM2.5 natural decay. Through this method, effective PM2.5 control ways during cooking in apartments can be proposed, such as natural ventilation with a range hood for 30 min and then the operation of an air purifier for 30 min. Additionally, if this prediction is combined with energy consumption, it will be possible to propose the most energy‐efficient indoor PM2.5 control methods for various seasons and outdoor conditions. [ABSTRACT FROM AUTHOR]

During wildfire smoke events public health agencies release advisories to stay indoors, close doors and windows, and operate a portable air cleaner (PAC). The do‐it‐yourself (DIY) air cleaner consisting of a box fan and a furnace filter is a widely used low‐cost alternative to commercial PACs because of its increased accessibility. In this study, we evaluate the clean air delivery rate (CADR) of different DIY air cleaner designs for reducing simulated wildfire smoke and identify operating parameters that may impact their performance and use. The simplest formulation of a DIY air cleaner (box fan with taped on minimum effectiveness reporting value – [MERV] 13 furnace filter) had a CADR of 111.2 ± 1.3 ft3/min (CFM). Increasing the fan flow by changing the fan type, increasing the fan setting, or reducing the pressure drop across the filtering surface increased the CADR. Large increases in CADR could be obtained by using a shroud (40%), using a 4″ thick filter (123%) using two filters in a wedge shape (137%), or using four filters in a Corsi‐Rosenthal (CR) box design (261%). The CADR was greatly reduced with filters heavily loaded with smoke, pointing to the need for frequent filter changes during smoke events. [ABSTRACT FROM AUTHOR]

In this study, the performance of a portable air cleaner, which is used to clean the air of a room with a person sitting in it, was investigated. The effects of different blowing angles and flow rates from the air supply vent on the device cleaning performance were investigated. In this context, air age and clean air delivery rate (CADR) parameters were calculated numerically. Randomly distributed particles in the room were tracked using the discrete phase model (DPM) and the relationship of pollutant concentrations with CADR and air age was examined. It has been seen that the blowing angle is an important parameter along with the flow rate. Moreover, it was concluded that the air age approach can be used to determine the performance of air cleaning devices. It has been found that the air cleaning device capture more than half of the particles in the environment, while the remaining particles are captured by other room surfaces. [ABSTRACT FROM AUTHOR]

The investigation of the cleaning effectiveness of air cleaners under realistic conditions is challenging. Mathematical models are needed to extract characteristic properties of the air cleaning system from experimental data. An incremental evaluation model based on a source term and a total first-order loss coefficient in each segment was developed to analyze indoor particle measurements. The application of the model is demonstrated using two scenarios, one in a well-mixed testing room and another in a fully equipped aircraft cabin at 750 hPa with a typical aircraft ventilation system. In the first scenario, a normalized version of the model is used to eliminate the source's influence. For the investigation in the aircraft cabin, the model served to extract temporal and spatial resolved source terms and first-order loss coefficients. The incremental evaluation model is applicable to enhance the certification of air cleaners. The application of the model is not only limited to particles; measurements of gaseous compounds like ozone, carbon dioxide, or volatile organic compounds can be evaluated analogously. The model's utility for the data analysis of experiments with complex flow conditions should be studied in further investigations. [ABSTRACT FROM AUTHOR]

It is important to control airborne particles in residential houses for protecting human health. Indoor particulate matter of <2.5 μm (PM2.5) can be effectively monitored and managed using an air purifier. In this study, the actual clean air delivery rates in residential houses (CADRActual) were acquired by comparing decay rates of fine particles with and without operations of the air purifier under actual conditions, following the standard CADR of an air purifier obtained in a closed test chamber. The measurements of CADRActual at different outdoor PM2.5 concentrations over a month in two residential houses revealed different airtightness levels, compared to the standardized clean air delivery rate of the air purifier (CADRAP). Air changes per hour at 50 Pa (ACH50) was 4.8 h−1 for "house A" (built in 2007) and 2.1 h−1 for "house B" (built in 2018). The CADR of the air purifier used in this study was 10.6 m3/min, while the averaged CADRActual at the "house A" was 7.2 m3/min (approximately 66% of the CADR of the air purifier) and 9.5 m3/min at "house B" (approximately 90% of the CADR of the air purifier). Under the outdoor PM2.5 concentrations of <35 μg/m3, the averaged CADRActual of house A and house B were 7.8 ± 0.3 and 9.7 ± 0.4 m3/min, respectively. However, under the outdoor PM2.5 concentrations of >35 μg/m3, the analogous averaged concentrations were 6.8 ± 0.6 and 9.6 ± 0.3 m3/min for houses A and B, respectively. The measured CADRActual agreed well with the theoretical estimates of CADRActual acquired by the mass balance equation using the infiltration rate of ACH50/20. We also estimated CADRActual/CADRAP for house C built in 2017, where the ACH50 was 1.8 h−1. Overall, this study demonstrated how CADRActual/CADRAP of an air purifier at residential houses can be predicted according to outdoor PM2.5 concentration and airtightness of the house. As shown, it can be closer to 1 at lower ACH50 houses and at lower outdoor PM2.5 concentrations. [ABSTRACT FROM AUTHOR]

Indoor PM2.5 must be effectively controlled to minimize adverse impacts on public health. Cooking is one of the main sources of PM2.5 in residential areas, and indoor air quality (IAQ) management methods such as natural and mechanical ventilation, range hood, and air purifier are typically used to reduce cooking-generated PM2.5 concentrations. However, studies on the combined effects of various IAQ management methods on indoor PM2.5 reduction and energy consumption are limited. In this study, a theoretical model was established to estimate the performance of various IAQ management methods for controlling indoor PM2.5 concentrations and energy consumption. The model was verified by comparative experiments in which, various IAQ management methods were operated individually or combined. Seasonal energy consumption was calculated through the verified model, and energy consumption saving scenarios were derived for maintaining indoor PM2.5 concentrations less than 10 μg/m3, a World Health Organization annual guideline, under fair and poor outdoor PM2.5 concentrations of 15 and 50 μg/m3, respectively. Based on our results, we found that energy consumption could be reduced significantly by applying natural ventilation in spring, autumn, and summer and mechanical ventilation in winter. Our study identified efficient energy saving PM2.5 management scenarios using various IAQ management methods by predicting indoor PM2.5 concentration and energy consumption according to the annual life patterns of typical residents in South Korea. [ABSTRACT FROM AUTHOR]