ABSTRACT
Amid concerns over airflow-induced transmission of the COVID-19 virus in buildings frequented by large numbers of people, such as offices, the necessity for radiant ceiling heating panels has increased. This is due to the concern that the airflows emitted from the convection heating systems installed near the ceiling or windows for winter heating may be a major cause of COVID-19 transmission. In this study, we aim to evaluate thermal comfort under various indoor and outdoor environmental conditions of a building and present the thermal output conditions of the radiant ceiling heating panel that can replace the convection heating system while ensuring comfort in the perimeter zone and handling the heating load. As a result, we were able to present, in a chart format, the thermal output conditions that can secure thermal comfort by analyzing the indoor airflow distribution depending on the surface temperature of the radiant ceiling heating panel, the interior surface temperature of the window, and the influence of internal heat generation. Moreover, through derived empirical formulas, we were able to determine the heating conditions of the panel that can secure the necessary heat dissipation while minimizing discomfort, such as downdrafts, even for indoor and outdoor conditions that were not evaluated in this study.
ABSTRACT
Dental services are yet to return to a semblance of normality owing to the fear and uncertainty associated with the possible airborne transmission of diseases. The present study aims to investigate the impacts of environmental conditions [changes in ventilation location, ventilation rate, and relative humidity (RH)] and variations in dental patient's breathing rate on droplet transmission during dental service. Computational fluid dynamics simulation was performed based on our previous experimental study during ultrasonic scaling. The impacts of different factors were numerically analyzed by the final fate and proportion of emitted droplets in the dental surgery environment. The results revealed that about 85% of droplets deposited near the dental treatment region, where the patient's torso, face, and floor (dental chair) accounted for around 63%, 11%, and 8.5%, respectively. The change in the ventilation location had a small impact on the deposition of larger droplets (> 60 mu m), and a spatial region with high droplet mass concentration would be presented near the dental professional. The change in the ventilation rate from 5 to 8 ACH led to a 1.5% increment in the fraction of escaped droplets. 50% RH in dental environments was recommended to prevent droplets' fast evaporation and potential mold. Variations in the patient's breathing rate had little effect on the final fate and proportion of emitted droplets. Overall, environmental factors are suggested to maintain 50% RH and larger ACH in dental surgery environments. The findings can give policymakers insights into the role of environmental factors on infection control.
ABSTRACT
To find out the circumstances under which airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) would happen, we conducted mechanistic and systematic modelling of two Coronavirus disease 2019 (COVID-19) outbreaks, i.e., Hunan 2-bus outbreak and Luk Chuen House outbreak (the horizontal cluster). Computational fluid dynamics (CFD) simulations, multi-zone airflow modelling, multi-route mechanistic modelling, and dose-response estimation were carried out selectively according to the transmission characteristics in each outbreak. Our results revealed that poorly ventilated bus indoor environments bred the Hunan 2-bus outbreak in which airborne transmission predominates;prevailing easterly background wind and probable door opening behaviour led to the secondary infections across the corridor in Luk Chuen House outbreak. Measures to facilitate sufficient ventilation indoors and positive pressure in the housing building corridor may help minimise infection risk. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
This post-occupancy study aims to assess the indoor air quality (IAQ) and ventilation performance in workshops and laboratories of a UK university during the COVID-19 pandemic. Supply airflow rates and CO2 were monitored as a proxy for evaluating ventilation performance. Additionally, particulate matter (PM10) was monitored to address the occupant's concerns about dust. Monitoring showed that maximum CO2 values recorded are mostly below 1000 ppm, with weekly averages below 520 ppm. This was expected as the supply airflow rates were significantly larger than recommended 10 l/s per occupant. Despite the large flow rates, PM10 levels in some laboratories were above the threshold value of 50 [μg/m3] supporting the poor IAQ claims of the occupants. The study indicated the room air re-circulation and indoor activities as the likely reasons for the elevated PM10 levels and some practical operational solutions were suggested for IAQ concerns. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The coronavirus disease may spread by airborne aerosols, especially in a poorly ventilated enclosure. Natural ventilation can reduce the transmission of infection. The WHO suggested the minimum ventilation rate of 10 L/s/person in non-residential settings. The objective was to evaluate risk of airborne infection with different settings in natural ventilated classroom. The risk was evaluated by using the modified Wells-Riley equation associated with the variation of contaminant concentration simulated by a multi-zone airflow model. The results provide the guidance of natural ventilation strategy in the classroom to reduce the transmission of airborne infection disease. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The COVID-19 pandemic has created a new type of waste (surgical mask waste "WMs") that presents a major challenge now and in the future, given the strong possibilities of similar epidemics to reoccur. In order to find an effective industrial solution to the millions of WMs produced daily, this research aims to develop a new eco-friendly strategy to convert WMs into H-2-CH4-rich syngas, carbon nanoparticles (CNPs), and benzene-rich tar using an updraft gasifier system. The experiments started with the preparation of WM granules using shredding followed by granulation processes. Subsequently, the granules were processed in a lab-scale reactor with a capacity of 0.9-1 kg/h and consisted of a continuous WM feed system, a gasifier, a sampling system for syngas and tar, a ceramic filtration unit for separating the CNPs against the synthesis gas, and a burner. The gasification experiments were performed in ambient air with different air-fuel equivalence ratios (ER: 0.21, 0.25, and 0.29) and temperatures (700 degrees C, 800 degrees C, and 900 degrees C) to determine the optimal conditions that yield the maximum amount of H-2-CH4-rich syngas and CNPs with less impurities. The chemical composition and morphology of the obtained gasification products (syngas, tar, and CNPs) were observed using GC-FID, FTIR, and SEM. The results showed that the maximum production of syngas (4.29 +/- 0.16 kg/h with HHV of 3804 kJ/kg) and CNPs (0.14 +/- 0.011 kg/h) accompanied by a moderate tar rate (0.123 +/- 0.009 kg/h with HHV of 41,139.88 kJ/kg) could be obtained at 900 degrees C and ER = 0.29, while the highest H-2 (16.93 +/- 1.7 vol.%) and CH4 (10.44 +/- 0.85 vol.%) contents in syngas product were synthesized at 900 degrees C and ER = 0.19. Benzene and toluene were the major GC-FID compounds in the formulated tar product with abundance up to 25.6% and 11%, respectively. Meanwhile, gasification conditions of 900 degrees C and ER = 0.24 allowed the best morphology to be formulated for spherical-shaped CNPs with a diameter of less than 200 nm.
ABSTRACT
The sustainability and progress of humanity depend on a clean, pollution-free environment, which is essential for good health and hygiene. Huge indoor auditorium does not have proper ventilation for air flow so when the auditorium is crowded the carbon di-oxide is emitted and it stays there for many days this may be a chance to spreading of COVID-19 and other infectious diseases. Without proper ventilation virus may present in the indoor auditorium. In the proposed system, emissions are detected by air, noise, and dust sensors. If the signal limit is exceeded, a warning is given to the authorities via an Android application and WiFi, and data is stored in cloud networks. In this active system, CO2 sensor, noise sensor, dust sensor, Microcontroller and an exhaust fan are used. This ESP-32 based system is developed in Arduino Integrated Development Environment (Aurdino IDE) to monitor air, dust and noise pollution in an indoor auditorium to prevent unwanted health problems related to noise and dust. More importantly, using IoT Android Application is developed in Embedded C, which continuously records the variation in levels of 3 parameters mentioned above in cloud and display in Android screen. Also, it sends an alert message to the users if the level of parameters exceeds the minimum and maximum threshold values with more accuracy and sensitivity. Accuracy and sensitivity of this products are noted which is very high for various input values. © 2022 IEEE.
ABSTRACT
Infection containment in the post-pandemic scenario became a top priority for healthcare engineering control staffers, especially in pneumology sectors, where the treatment of airborne infectious diseases is frequent. In Brazil, where COVID-19 left a long record of casualties, there is a lack of information on the influence of filtration systems on the maintenance of regulated operational conditions for indoor comfort in hospital environments. This paper has the following objectives: to study arrangements of filtering systems in hospital acclimatization ducts;to verify how filtering characteristics could compromise safety regulations for airflow in hospital environments;and to identify airflow stagnation points that might favor suspended viral concentrations and increase contamination risks. We used the computational fluid dynamics STAR-CCM+© software to perform numerical simulations of different cases of indoor airflow in a model corresponding to a sector of the Lauro Wanderley University Hospital (João Pessoa city, Brazil). We concluded that standards for maximum velocity are reachable despite thinner or thicker filters affecting the spread of the air. In this way, acclimatization systems are limited by a tradeoff between regulation and protection. Our findings are relevant to future technological development, interventions, safety strategies amidst contamination scenarios, and new filtration arrangements in hospital environments.
ABSTRACT
Since the beginning of the COVID19 pandemic, there has been a lack of data to quantify the role played by breathing-out of pathogens in the spread of SARS-Cov-2 despite sufficient indication of its culpability. This work aims to establish the role of aerosol dispersion of SARS-Cov-2 virus and similar airborne pathogens on the spread of the disease in enclosed spaces. A steady-state fluid solver is used to simulate the air flow field, which is then used to compute the dispersion of SARS-Cov-2 and spatial probability distribution of infection inside two representative classrooms. In particular, the dependence of the turbulent diffusivity of the passive scalar on the air changes per hour and the number of inlet ducts has been given due consideration. By mimicking the presence of several humans in an enclosed space with a time-periodic inhalation-exhalation cycle, this study firmly establishes breathing as a major contributor in the spread of the pathogen, especially by superspreaders. Second, a spatial gradient of pathogen concentration is established inside the domain, which strongly refutes the well-mixed theory. Furthermore, higher ventilation rates and proximity of the infected person to the inlet and exhaust vents play an important role in determining the spread of the pathogen. In the case of classrooms, a ventilation rate equivalent to 9 air changes or more is recommended. The simulations show that the "one-meter distance rule"between the occupants can significantly reduce the risk of spreading infection by a high-emitter. © 2023 Author(s).
ABSTRACT
This study aims to present a smart ventilation control framework to reduce the infection risk of COVID-19 in indoor spaces of public buildings. To achieve this goal, an artificial neural network (ANN) was trained based on the results from a parametric computational fluid dynamics (CFD) simulation to predict the COVID-19 infection risk according to the zone carbon dioxide (CO2) concentration and other information (e.g., zone dimension). Four sample cases were analyzed to reveal how the CO2 concentration setpoint was varied for a given risk level under different scenarios. A framework of smart ventilation control was briefly discussed based on the ANN model. This framework could automatically adjust the system outdoor airflow rate and variable air volume (VAV) terminal box supply airflow rate to meet the needs of reducing infection risk and achieving a good energy performance. © International Building Performance Simulation Association, 2022
ABSTRACT
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
With increasing the COVID-19 pandemic and the time spent indoor, there is a growing research interest in the issue of Indoor Environmental Quality in building including thermal environment and indoor air quality (IAQ). Research and intervention in schools are a particular focus, as children are especially vulnerable to air pollution. The aim of this study is to assess the impact of energy renovation, including the installation of a balanced ventilation system with a filter (F7 type), on the IAQ of a school building located in a polluted outdoor environment. The study is based on measurements of some parameters of thermal environment and IAQ. To this end, two classrooms were chosen for two measurement campaigns. Each campaign covered 2 months in winter in 2018 and 2020 before and after renovation, respectively. The measurements included ventilation airflow rates, temperature, relative humidity, carbon dioxide, and particle concentration (PM2.5). The main result of installing the balanced ventilation was an increase in the air change rate from 0.1 h−1 and 0.05 h−1 before the renovation to 1.5 h−1 and 1.7 h−1 after the renovation, for classroom 1 and classroom 2, respectively. This increase changed the ICONE air stuffiness level from average air stuffiness to fresh air (no air stuffiness). However, this increase resulted in a significant entry of outdoor particles. As consequence, the highest indoor/outdoor concentration ratio (57%) was observed after the renovation. All these results highlights that ventilation performance should be extended to parameters as filtration efficiencies in order to increase IAQ. © 2023 Elsevier Ltd
ABSTRACT
Airborne transmission via aerosol particles without close human contact is a possible source of infection with airborne viruses such as SARS-CoV-2 or influenza. Reducing this indirect infection risk, which is mostly present indoors, requires wearing adequate respiratory masks, the inactivation of the viruses with radiation or electric charges, filtering of the room air, or supplying ambient air by means of ventilation systems or open windows. For rooms without heating, ventilation, and air conditioning (HVAC) systems, mobile air cleaners are a possibility for filtering out aerosol particles and therefore lowering the probability of indirect infections. The main questions are as follows: (1) How effectively do mobile air cleaners filter the air in a room? (2) What are the parameters that influence this efficiency? (3) Are there room situations that completely prevent the air cleaner from filtering the air? (4) Does the air cleaner flow make the stay in the room uncomfortable? To answer these questions, particle imaging methods were employed. Particle image velocimetry (PIV) was used to determine the flow field in the proximity of the air cleaner inlet and outlet to assess regions of unpleasant air movements. The filtering efficiency was quantified by means of particle image counting as a measure for the particle concentration at multiple locations in the room simultaneously. Moreover, different room occupancies and room geometries were investigated. Our results confirm that mobile air cleaners are suitable devices for reducing the viral load indoors. Elongated room geometries, e.g., hallways, lead to a reduced filtering efficiency, which needs to be compensated by increasing the volume flow rate of the device or by deploying multiple smaller devices. As compared to an empty room, a room occupied with desks, desk separation walls, and people does not change the filtering efficiency significantly, i.e., the change was less than 10%. Finally, the flow induced by the investigated mobile air cleaner does not reach uncomfortable levels, as by defined room comfort standards under these conditions, while at the same time reaching air exchange rates above 6, a value which is recommended for potentially infectious environments.
ABSTRACT
A dimensionless number Nr for the effective design of facial masks was derived and compared with other dimensionless numbers of fluid mechanics. Nr is found to closely resemble Euler's number (Eu). Nr is equal to the logarithmic function of the ratio of inertial force (Fi) of the air to the pressure force (Fp) of the air through the porous membrane of the mask. Nr is then introduced as a novel dimensionless number (Habib number) Ha in which the air flow through a facial mask is derived with parameters for an effective barrier from the COVID-19 virus (SARS COV 2). The introduction of Ha was not only for a comparison reason with other dimensionless numbers of fluid mechanics but also the number Ha is an essential extension of an early work on "Fluid mechanics of facial masks as personal protection equipment (PPE) of COVID-19 virus"[Rev. Sci. Instrum. 92, 074101 (2021)], in which the air flow through the mask is in its optimum design conditions to shield against the COVID-19 virus. As a result, an optimum Nr of expressing the flow of the O2 and N2 gases through the porous membrane was determined (Nr = NO2 = NN2 = Ha = -4.4). This was obtained when the N95 mask with specifications of a = 20 nm, l = 30 μm, and ϵ = 30% was used, with respect to the pressure gradient of the human lungs during exhaled and inhaled conditions, PAverage = 20 mm Hg (g cm-1 S-2), and to the size of the COVID-19 virus of about 125 nm (0.125 μm). In addition, a range of values of Nr was analyzed with respect to the optimum (Ha) value of Nr. On the one hand, when the range value of Nr falls between 0 ≥ Nr ≥ Ha, the mask has less resistance than Nr < -4.4, but not necessarily its optimum design conditions. On the other hand, when Nr = 0, the flow through the mask has no resistance at all, as if the mask does not exist. © 2023 Author(s).
ABSTRACT
OBJECTIVE: To explore the air environment control in ship negative pressure ward and conduct the risk assessment. METHODS: STARCCM+ simulation software was employed to simulate the air environment in the negative pressure ward of ships, and the impact of ventilation volume, non-equilibrium pressure difference and open/close door disturbance on the flow of polluted gas in the ward and the pressure control between compartments was observed. RESULTS: It was found that the pressure gradient and airflow direction of adjacent cabins were basically the same under different ventilation conditions;the pressure fluctuation of the medical corridor had the greatest impact on the buffer room, and when the negative pressure fluctuated higher than the design value, the pressure difference between the buffer room and the negative pressure ward was lower than the design requirement of 5 Pa;when the cabin door was opened from the buffer room to the corridor, that was, when the cabin door was opened to an area with low negative pressure, a low pressure area appears in the buffer room, and the polluted air flowed from the corridor to the buffer room. Finally, the risk of airborne infection was assessed by using the Wells-Riley model, doubling the amount of ventilation reduced the probability of transmission of SARS-CoV-2 infection by about 100%. The results showed that the ventilation volume had little effect on the pressure control, but it wound affect the probability of transmission of viral infection;the pressure fluctuation in a certain compartment would affect the pressure in other areas, so that the pressure control between the compartments did not meet the design requirements, opening the hatch door to the area with low negative pressure could reduce the risk of virus transmission. CONCLUSION: The research provides guidance for the air environment control in the ship's negative pressure isolation ward so as to prevent the spread of infectious diseases in the ship.
ABSTRACT
Current research on airborne transmission of African swine fever virus (ASFV), porcine epidemic diarrhoea virus (PEDV), avian influenza (AIV), porcine reproductive and respiratory syndrome virus (PRRSV), and foot and mouth disease virus (FMDV) was reviewed to evaluate commonalities, knowledge gaps, and methodologies of studying airborne transmission of animal diseases. The reviewed studies were categorised as short-range transmission (within a single facility) and long-range transmission (beyond a single site). Short-range airborne transmission was demonstrated for at least one strain of the above-mentioned pathogens in experimental settings. Most studies reported in the literature concern FMDV, with limited information for ASFV and PEDV, particularly for short-range airborne transmission. Air sampling upwind, downwind, and within infected facilities has been commonly used to demonstrate long-range airborne transmission. The amount of evidence from air sampling for each of the reviewed viruses varies from no evidence on ASFV to evidence from multiple settings for AIV. Computer modelling has been used to study past outbreaks of infectious diseases to assess the contribution of airborne transmission with a multitude of computer models reported in the literature for simulating long-range airborne transmission of FMDV based on past outbreaks. This has resulted in predictive tools for assessing future risk of airborne transmission. Some important computer models are based on epidemiology analysis, weather analysis, and air dispersion. Few models are reported for ASFV, PEDV, and PRRSV. Studies in the literature indicate that airborne transmission is generally affected by virus strain, aerosol type, shedding duration and concentration, environmental conditions, and infectious dose.
ABSTRACT
The wind environment in residential areas can exert a direct or indirect influence on the spread of epidemics, with some scholars paying particular attention to the epidemic prevention and control of residential areas from the perspective of wind environments. As a result, it is urgent to re-examine the epidemic prevention response of residential spaces. Taking high-rise residential areas in Xi'an as an example, the article defines the air flow field area based on on-site wind environment measurements, crowd behavior annotation, and CFD simulation. Using the double-effect superposition of crowd behavior and risk space, the paper undertook a multiple identification strategy of epidemic prevention space. The identification methods and management and control strategies of epidemic prevention in high-rise residential areas are proposed. Additionally, the living environment of residential areas is optimized, and a healthy residential space is created. The transformation from concept and calls for action to space implementation is made to provide a reference for improving the space management and control capabilities in high-rise residential areas in China. The results of this study can be used as a guideline for future residential planning and design from the perspective of preventing airborne diseases.
ABSTRACT
Indoor air quality is a crucial factor when evaluating habitability, especially in developed countries, where people spend most of their time indoors. This paper presents a novel double skin façade (DSF) system that combines physical and photocatalytic filtering strategies. The air purification system is made up of fixed slats that are both solar protection and air purification system. The objective of this work is to determine the thermal behaviour of the proposed system, so that its suitability for use in various environments may be assessed. This was carried out using a physical 1:1 scale model and a computational fluid dynamics (CFD) model. The maximum temperature inside the scale model cavity was 17–20 °C higher than outdoor air. Additionally, it was discovered that the airflow through the DSF would require forced ventilation. To determine the emissivity values of the photocatalytic coating, additional experimental measurements were made. The CFD model was tested for summer and winter conditions in Barcelona, Chicago, and Vancouver. The average increase in the intake air temperature was around 14.5 °C in winter and 12 °C in summer, finding that the system has its main use potential in temperate or cold areas with many hours of solar radiation.
ABSTRACT
This work presents the development of an individual protection device, a smart and active ventilated face shield that can also incorporate an air filtering system. The device can work with the front shield or just with the ventilation structure. The system was produced by additive manufacturing technology, based on a chassis that incorporates an electronic control unit, a rechargeable battery, a fan, and a humidity/temperature sensor. The performed system tests showed that the forced ventilation system prevents fogging even in the most adverse situations and increases user comfort when it is used simultaneously with an individual protective face mask, due to the air flow generated by the integrated fan. The filtered ventilated air guarantees the user's safety. Results also show that, with or without the front visor, the equipment prevents fogging, both on the face shield and glasses for users who wear them. The forced air flow promotes isolation of the breathing zone, decreasing the contact with potentially contaminated aerosols, thus reducing the risk of contagion. © 2022 IEEE.
ABSTRACT
This work presents the development of an individual protection device, a smart and active ventilated face shield that can also incorporate an air filtering system. The device can work with the front shield or just with the ventilation structure. The system was produced by additive manufacturing technology, based on a chassis that incorporates an electronic control unit, a rechargeable battery, a fan, and a humidity/temperature sensor. The performed system tests showed that the forced ventilation system prevents fogging even in the most adverse situations and increases user comfort when it is used simultaneously with an individual protective face mask, due to the air flow generated by the integrated fan. The filtered ventilated air guarantees the user's safety. Results also show that, with or without the front visor, the equipment prevents fogging, both on the face shield and glasses for users who wear them. The forced air flow promotes isolation of the breathing zone, decreasing the contact with potentially contaminated aerosols, thus reducing the risk of contagion. © 2022 IEEE.