Simulation Study on Airflow Organization and Environment in Reconstructed Fangcang Shelter Hospital Based on CFD

With frequent outbreaks of COVID-19, the rapid and effective construction of large-space buildings into Fangcang shelter hospitals has gradually become one of the effective means to control the epidemic. Reasonable design of the ventilation system of the Fangcang shelter hospital can optimize the indoor airflow organization, so that the internal environment can meet the comfort of patients and at the same time can effectively discharge pollutants, which is particularly important for the establishment of the Fangcang shelter hospital. In this paper, through the reconstruction of a large-space gymnasium, CFD software is used to simulate the living environment and pollutant emission efficiency of the reconstructed Fangcang shelter hospital in summer under different air supply temperatures, air supply heights and exhaust air volume parameters. The results show that when the air supply parameters are set to an air supply height of 4.5 m, an air supply temperature of 18 °C, and an exhaust air volume of a single bed of 150 m3/h, the thermal comfort can reach level I, and the ventilation efficiency for pollutants can reach 69.6%. In addition, the ventilation efficiency is 70.1% and 70.3% when the exhaust air volume of a single bed is continuously increased to 200 and 250 m3/h, which can no longer effectively improve the pollutant emission and will cause an uncomfortable blowing feeling to patients. © 2023 by the authors.

The effect of ventilation performance on risk of indoor airborne transmission of SARS-CoV-2

Ventilation performance plays a significant role in distributing contaminants and airborne infections indoors. Thus, poorly ventilated public spaces may be at high risk due to the presence of both infectious and susceptible people. Adapting HVAC ventilation systems to mitigate virus transmission requires considering ventilation rate, airflow patterns, air balancing, occupancy, and feature placement. The study aims to identify poorly ventilated spaces where airborne transmission of pathogens such as SARS-CoV-2 could be critical. This study is focused on evaluating the ventilation performance of the building stock and the safety of using the facilities based on measured indoor CO2. The results revealed the spaces with the potential risk of indoor airborne transmission of COVID-19. The study proposes recommendations for utilising air ventilation systems in different use cases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Investigation into workplace ventilation at COVID-19 outbreak sites

Site visits were made to ten (non-healthcare) workplace COVID-19 outbreaks to assess ventilation. Measurements of carbon dioxide (CO2), temperature and humidity were made. Room activity and occupancy was observed, and ventilation management assessed. CO2 readings were used to identify areas of poor air quality, and where possible, airflow measurements were made at ventilation openings and CO2 decay rates were used to estimate ventilation rates. Poorly ventilated, regularly occupied spaces were frequently identified by this work. Measures to reduce transmission risk and improve ventilation included opening windows and reducing room capacities. Attempts at reconfiguration of mechanical ventilation systems were not common. Thermal comfort and heating costs were factors cited that influenced decision making. Overall understanding of ventilation was low and identified a need for simple tools to allow stakeholders to assess their workspaces. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Assessment of diffuse ceiling ventilation performance on transmission of airborne infectious diseases

Ventilation systems have been widely used to satisfy the occupants' indoor air quality and thermally comfort conditions. Various air distribution systems have been developed to supply clean air, including mixing, displacement, and diffuse ceiling ventilation systems. Diffuse ceiling systems are recent air distribution systems that supply cold air to the occupant area using perforated diffuse panels. These systems distribute air with a low velocity, minimizing the draft risk and dissatisfaction in highly dense spaces. The transmission risk of airborne infectious diseases like Covid-19 from the infected patient is high in waiting rooms. Thus, there is a demand to assure a secure environment for medical staff and patients in the waiting rooms. This study aims to numerically investigate the impact of the relative distance of the contamination source and exhaust on the transmission of airborne infectious diseases in the waiting room equipped with the diffuse ceiling ventilation system. In this regard, the release of Covid-19 from 4 different patients was investigated separately using the computational fluid dynamics technique. The distribution of the airborne infectious diseases is simulated by releasing SF6 tracer gas. The simulation result revealed that the contaminated patient located adjacent to the room's outlet had no contamination risk for other patients and staff in the waiting room. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Aerodynamic performance of a ventilation system for droplet control by coughing in a hospital isolation ward.

Over 766 million people have been infected by coronavirus disease 2019 (COVID-19) in the past 3 years, resulting in 7 million deaths. The virus is primarily transmitted through droplets or aerosols produced by coughing, sneezing, and talking. A full-scale isolation ward in Wuhan Pulmonary Hospital is modeled in this work, and water droplet diffusion is simulated using computational fluid dynamics (CFD). In an isolation ward, a local exhaust ventilation system is intended to avoid cross-infection. The existence of a local exhaust system increases turbulent movement, leading to a complete breakup of the droplet cluster and improved droplet dispersion inside the ward. When the outlet negative pressure is 4.5 Pa, the number of moving droplets in the ward decreases by approximately 30% compared to the original ward. The local exhaust system could minimize the number of droplets evaporated in the ward; however, the formation of aerosols cannot be avoided. Furthermore, 60.83%, 62.04%, 61.03%, 60.22%, 62.97%, and 61.52% of droplets produced through coughing reached patients in six different scenarios. However, the local exhaust ventilation system has no apparent influence on the control of surface contamination. In this study, several suggestions with regards to the optimization of ventilation in wards and scientific evidence are provided to ensure the air quality of hospital isolation wards.

Effect of energy renovation on indoor air quality and thermal environment in winter of a primary school in a highly polluted French alpine valley

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

Experimental study on the control effects of different strategies on particle transportation in a conference room: Mechanical ventilation, baffle, portable air cleaner, and desk air cleaner.

To control the spread and transmission of airborne particles (especially SARS-CoV-2 coronavirus, recently) in the indoor environment, many control strategies have been employed. Comparisons of these strategies enable a reasonable choice for indoor environment control and cost-effectiveness. In this study, a series of experiments were conducted in a full-scale chamber to simulate a conference room. The control effects of four different strategies (a ventilation system (320 m3/h) with and without a baffle, a specific type of portable air cleaner (400 m3/h) and a specific type of desk air cleaner (DAC, 160 m3/h)) on the transportation of particles of different sizes were studied. In addition, the effects of coupling the ventilation strategies with five forms of indoor airflow organization (side supply and side or ceiling return, ceiling supply and ceiling or side return, floor supply and ceiling return) were evaluated. The cumulative exposure level (CEL) and infection probability were selected as evaluation indexes. The experimental results showed that among the four strategies, the best particle control effect was achieved by the PAC. The reduction in CEL for particles in the overall size range was 22.1% under the ventilation system without a baffle, 34.3% under the ventilation system with a baffle, 46.4% with the PAC, and 10.1% with the DAC. The average infection probabilities under the four control strategies were 11.3-11.8%, 11.1-11.8%, 9.1-9.5%, and 18.2-19.7%, respectively. Among the five different forms of airflow organization, the floor supply and ceiling return mode exhibited the best potential ability to remove particles.

A numerical study of COVID-19-laden droplets dispersion in aircraft cabin ventilation system.

Ventilation systems for aircraft cabins are mainly used to maintain a comfortable environment in the cabin and ensure the health of passengers. This study evaluates the decontamination performance of two cabin ventilation systems, the displacement ventilation (DV) system and the mixing ventilation (MV) system, in preventing contamination by virus (COVID-19)-laden droplets. The Euler-Lagrange method was used to computationally model droplet dispersion of different diameters and their behavior in the two systems was contrastively analyzed. Statistics on droplet suspension ratios and duration as well as the infection probability of each passenger were also computed. It was found that11.07% fewer droplet remained suspended in the DV system were than those in the MV system 10s from droplet release. In addition, the number of droplets extracted from the exhausts in the DV system was 13.15% more than the MV system at the 400s mark. In the DV system, higher ambient wind velocities were also found to locally increase infection probability for passengers in certain locations.

Air curtain as a SARS-CoV-2 spreading mitigation method in a small aircraft cabin

This paper discusses an application of air curtain for reduction of virus-laden droplets transmission from an infected host to other passengers in a small aircraft cabin. The study is restricted to respiratory droplets emitted during coughing. Discrete Particle Method introduced for violent respiratory events (VRE) captured in detail the movement of coughing puff inside the cabin and allowed to study the interaction of droplets with the air curtain's stream and the surrounding air. The results show that the application of the air curtain inhibits the transmission process of small droplets (diameters ranging from 10 to 40 mu m). The air curtain supplied with a limited air mass flow cannot alter the multiphase puff dynamics, but it can be utilized to deflect the virus droplets with lower momentum away from the neighboring passenger. Improved removal efficiency of virus-laden droplets has been achieved owing to the application of the air curtain together with supplementary suction surfaces introduced on the front seat backrest. The virus (SARS-CoV-2) transmission process was also analyzed by means of mass concentration of CO2 exhaled by the infected host, used as a contamination tracker. This part of the work aims at assessment of an applicability of CO2 tracer gas in analysis of virus transmission. Results show that CO2 tracer gas can only be employed for the study of small size droplets dispersion (diameter less or equal to 40 mu m).

Experimental studies of the effectiveness of UV irradiation for supply ventilation systems of ship premises

The air environment is favorable for the reproduction of microorganisms and viruses. The problem has become particularly urgent in connection with the Cov19 coronavirus pandemic, which undoubtedly affected the operation of all types of fleet. The need for a concealed installation of an air disinfection device is due to safety requirements during the operation of the vessel. The recirculators currently in use are not elements of shipboard ventilation systems. The article proposes the modernization of this system using an integrated air disinfection unit. A schematic diagram of such an installation is proposed. An experimental stand has been developed to determine the effectiveness of air disinfection by studying microbial contamination. The planning and processing of the experiment results were carried out using a software product. A mathematical model has been developed for the operation of the supply air disinfection unit in the ship's ventilation system, which provides the necessary efficiency with minimal energy and heat costs for air treatment.

Airborne migration behaviour of SARS-CoV-2 coupled with varied air distribution systems in a ventilated space

Air distribution system could critically affect SARS-CoV-2 transmission in indoor space;therefore, this study aims at demonstrating numerical characteristics of SARS-CoV-2 migration with varied air distribution system configurations. Seven cases were investigated regarding three major aspects: how fast suspended particles can be removed from the ventilated space or changed into deposited particles;how much particles are attached to various object surfaces which leads to an infection by touching fomite. All cases were analyzed through computational fluid dynamics (CFD). Both different shapes (round or linear diffusers) and installation locations (ceiling or floor) of inlet and outlet diffusers were investigated. Results showed that different air distribution system would lead to different dispersion profiles of infectious particles and different deposition pattern of particles on interior surfaces. With the same air flow rate, linear-diffuser would perform better for CO2 extraction while requiring less time to remove or collide the same magnitude of suspended droplets compared to round-diffuser. However, how quickly removed or suspended droplets collide is not proportional to how less the number of total particles are remained. Two additional cases with double sized space possessing best ventilation configuration were also examined to explore potential application of the best-ventilated configuration to various spatial expansion cases.

Impact of human'human virus transmission in an air-conditioned room with proper ventilation system

As we are probably aware of certain infectious diseases that transmit from body to body because of perspiration or respiration of air from a human being containing strains of the infection, the goal of this investigation is to see how the infection is getting spread from a human residing in a closed area provided with air conditioner and with an appropriate ventilation framework that need to be involved to diminish infection dissemination in this enclosed area. Considering the present COVID-19 situation, it is important to discover the effect of infection spread to an individual contagion source. An appropriate CFD-model giving analysis of infection transmission from individual to individual in an air-conditioned room would give results to understand such situations. Likewise, this examination would help in determining the velocity, temperature, and particle contours in a characterized walled area. Besides, we have displayed various nooks utilizing different ventilation frameworks to discover which framework would give better outcomes to decrease infection transmission. Our investigation would provide how varying flow rates in a room at an outlet could be effective in reducing virus dissemination, as this model could be applied to cafes, cinemas, inns, and above all emergency clinics where individuals remain in an enclosed air-conditioned room. © C. Manas et al., Published by EDP Sciences, 2022.

Estimation of Occupancy Using IoT Sensors and a Carbon Dioxide-Based Machine Learning Model with Ventilation System and Differential Pressure Data.

Infectious diseases such as the COVID-19 pandemic have necessitated preventive measures against the spread of indoor infections. There has been increasing interest in indoor air quality (IAQ) management. Air quality can be managed simply by alleviating the source of infection or pollution, but the person within a space can be the source of infection or pollution, thus necessitating an estimation of the exact number of people occupying the space. Generally, management plans for mitigating the spread of infections and maintaining the IAQ, such as ventilation, are based on the number of people occupying the space. In this study, carbon dioxide (CO2)-based machine learning was used to estimate the number of people occupying a space. For machine learning, the CO2 concentration, ventilation system operation status, and indoor-outdoor and indoor-corridor differential pressure data were used. In the random forest (RF) and artificial neural network (ANN) models, where the CO2 concentration and ventilation system operation modes were input, the accuracy was highest at 0.9102 and 0.9180, respectively. When the CO2 concentration and differential pressure data were included, the accuracy was lowest at 0.8916 and 0.8936, respectively. Future differential pressure data will be associated with the change in the CO2 concentration to increase the accuracy of occupancy estimation.

Non-contact Screening Center of Infectious Diseases for Cross Infection Prevention-Focusing on the Viral Aerosol Removal Efficiency by a Ventilation System

In this study, to fundamentally solve the risk of cross-infection in screening centers responding to infectious diseases, a new non-contact screening center was developed that supplemented the problems of existing screening centers. Numerical analysis was performed on the effectiveness of a ventilation system to remove viral aerosols and prevent cross-infection. Moreover, full-scale field measurements and SF6 tracer gas simulating viral aerosol was used under the same conditions as it was for the numerical analysis, comparison, and verification when CFD simulations were performed. Currently, COVID-19 screening centers operating in Korea can be divided into five types;the risk of cross-infection is very high due to its structure where the movement of medical staff and suspected patients cannot be separated. As a result of the CFD simulation on the ventilation system of a non-contact screening center, among the 3,000 particles generated from a patient, not a single particle was transmitted from the specimen collection booth to the adjacent examination room. More than 99% of the particles were removed by the ventilation system after 559 seconds. As a result of the in-situ measurement, the concentration of SF6 gas generated in the specimen collection booth was effectively reduced by the ventilation system. Additionally, the SF6 gas was not detected in the examination room due to the maintenance of an appropriate differential pressure. © 2022, Architectural Institute of Korea. All rights reserved.

Stratum Ventilation: Enabling Simultaneous Energy Conservation and Air Purification in Subway Cars.

The supply of fresh air for underground rail transit systems is not as simple as opening windows, which is a conventional ventilation (CV) measure adopted in aboveground vehicles. This study aims to improve contaminant dilution and air purification in subway car ventilation systems and the safety of rail transit post-coronavirus disease pandemic era. We designed an air conditioning (AC) terminal system combined with stratum ventilation (SV) to enable energy consumption reduction for subway cars. We experimentally tested the effectiveness of a turbulence model to investigate ventilation in subway cars. Further, we compared the velocity fields of CV and SV in subway cars to understand the differences in their airflow organizations and contaminant removal efficiencies, along with the energy savings of four ventilation scenarios, based on the calculations carried out using computational fluid dynamics. At a ventilation flow rate of 7200 m3/h, the CO2 concentration and temperature in the breathing areas of seated passengers were better in the SV than in the CV at a rate of 8500 m3/h. Additionally, the energy-saving rate of SV with AC cooling was 14.05%. The study provides new ideas for reducing the energy consumption of rail transit and broadens indoor application scenarios of SV technology.

Natural Ventilation and Air Purification for Effective Removal of Airborne Virus in Classrooms with Heater Operation.

Mass COVID-19 infection cases in indoor spaces have been continuously reported since its global outbreak, generating increasing public interest in reducing the spread of the virus. This study considered a situation in which an infected individual continuously releases the virus into the air in a classroom, simulated by continuous injection of NaCl particles ≤ 5 µm, with heater operation during winter. The effects of applying natural ventilation and operating one or two air purifiers on the removal of virus-containing aerosols were experimentally compared and analyzed based on the spatiotemporal changes in NaCl concentration within the classroom. When a heater was operated with all windows shut, operating one and two air purifiers reduced the amount of the aerosol in indoor air by approximately 50 and 60%, respectively, compared to the case with no air purifier. Additionally, when the heater was operated with one or two air purifiers under natural ventilation, the amount of virus-containing aerosol in the air was reduced by 86-88% compared to the case with neither natural ventilation nor air purifier. Because natural ventilation significantly varies with weather conditions and particulate matter concentrations, combining natural ventilation with air purifiers in classrooms during winter needs to be adjusted appropriately.

Exploration of the Emergency Renovation of Sports Venues Resilience Space Based on Green Building Technology Under the Normal Epidemic Situation

The sudden outbreak of COVID-19 has caused a surge in medical demand. It has inspired people to continuously explore how to transform public buildings such as gymnasiums in a fast, low-cost and green way during emergencies. The article studies the feasibility of applying gymnasium to sudden public events, discusses the design methods for the renovation of gymnasium space, water supply and drainage system, ventilation system and intelligent system in emergency situations. The focus is on preventing cross-contamination, preventing backflow contamination, pressure shaving, airflow organization, and system control. Through these design methods, the gymnasium has the characteristics of efficient, adaptable and inclusive epidemic prevention. The application prospect of green building technology in emergency reconstruction was explored, and a reference is put forward for the design and reconstruction of gymnasiums in the post-epidemic era with “combination of epidemic control” and improving the resilience space of gymnasiums. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Controller Design For Respiratory Systems Used During The Covid-19 Pandemic

During pandemics, Intensive care units (ICUs) play a major role in providing necessary medical treatment to the patients and stabilizing dire situations. Mechanical ventilation systems are an integral part of ICUs in every medical facility. A Mechanical Ventilation system must provide accurate and fast tracking of a pre-set pressure profile. Therefore various controller designs are tested and analyzed in the presented paper for a blower-hose-patient mechanical ventilation system. The basic framework for the control problem, and necessary mathematical and simulation background is presented along with a comparative analysis of the designed control schemes. An attempt is also made to find an optimal controller design providing the desired system output with minimal trade-offs. © 2022 IEEE.

Explosive COVID-19 outbreak in a German nursing home and the possible role of the air ventilation system.

BACKGROUND: Most COVID-19 outbreaks in nursing homes are explained by transmission of SARS-CoV-2 from nurses or visitors. METHODS AND RESULTS: We describe an outbreak with 64 of the 67 residents identified as COVID-19 cases within two weeks (34 in nursing block 1, 30 in nursing block 2), at least 32 of them had relevant symptoms of COVID-19. Thirteen of the residents' deaths were associated with COVID-19. In addition, 27 of approximately 60 staff members were identified as COVID-19 cases, 23 of them had relevant symptoms. In none of the samples from residents or staff was a mutation of SARS-CoV-2 detected. Quarantine of the residents was already in force at the beginning of the outbreak. A common source among the staff was considered to be unlikely because the two nursing home blocks had no staff rotation and the staff had to wear FFP2 masks during contact with residents. Three months after the outbreak the RNA of SARS-CoV-2 was detected on 14 of 39 sampled indoor surfaces of the air ventilation system with Ct values between 34.9 and 41.9, but only at the air supply in the corridor (11 of 24 samples) and the air overflow in the door between the corridor and the residents' rooms (three of 11 samples) but not at the air exhaust in the residents' bathrooms. CONCLUSIONS: The air ventilation system and an inversion weather situation three days before the first confirmed case may have enhanced viral spread inside the nursing home assuming that a common source with a high viral load had existed at the time of outbreak.

Measurement and Control of Surgical Smoke to Enhance Surgical Team Safety.

Amid the coronavirus disease 2019 era, concern about the safety of surgical teams related to surgical smoke (SS) is rising. As simple ventilation improvement methods (SVIMs), we replaced 4 of the 8 supply diffusers with a direction-adjustable louver-type, closed 2 of the 4 exhaust grills, and strengthened the sealing of the doorway. Dynamic changes in the concentration of particulate matter (PM) with sizes of < 1.0 µm (PM1.0) were measured using low-cost PM meters (LCPMs) at eight locations in the operating room (OR). SS concentration up to 4 minutes at the location of the surgeon, first assistant, and scrub nurse before and after SVIMs application decreased from 65.4, 38.2, 35.7 µg/m3 to 9.5, 0.1 and 0.7 µg/m3 respectively. A similar decrease was observed in the other 5 locations. SVIMs could effectively control SS and the LCPM was also effective in measuring SS in the OR or other spaces of the hospital.