Abstract:Controlling airborne transmission of contaminants including respired viruses such as SARS-CoV-2 is necessary to protect occupants living in the same house with a contagious person. The effectiveness of interventions requiring minor efforts that create a negative pressure isolation zone (IZ) for a contagious person has yet to be systematically tested for residential homes. In this study, ASHRAE Standard 170, which offers guidance for negative pressure isolation space control in healthcare facilities, was used i… Show more
“…Note that the remaining fresh air (30 m 3 /h) is reserved for the living room as shown in Figure 4(b). In system III, since the exhaust valves (E1, E2, E3 and E4) of the four bedrooms are open in turn, the mechanical exhaust system forms a negative pressure 42 in the bedroom with the exhaust valves open, while the other bedrooms are under normal pressure. For example, Figures 3(c) and (d) show the ventilation mode of system III in stage A and stage B as shown in Figure 4(c), respectively.Figure 3.Working conditions of different ventilation units under different ventilation modes: (a) system I with simultaneous replacement mode; (b) system II with simultaneous replacement mode; (c) system III in stage A and (d) system III in stage B.Figure 4.Operation mode of fresh air system under different ventilation systems: (a) system I with simultaneous replacement mode; (b) system II with simultaneous replacement mode and (c) system III with sequential replacement mode (t1 represents the time of each period).…”
Section: Methodsmentioning
confidence: 99%
“…Note that the remaining fresh air (30 m 3 /h) is reserved for the living room as shown in Figure 4(b). In system III, since the exhaust valves (E1, E2, E3 and E4) of the four bedrooms are open in turn, the mechanical exhaust system forms a negative pressure 42 in the bedroom with the exhaust valves open, while the other bedrooms are under normal pressure. For example, Figures 3(c) and (d) show the ventilation mode of system III in stage A and stage B as shown in Figure 4(c), respectively.…”
Section: Novel Type Of Indoor Fresh Air Ventilation Systemmentioning
Poor indoor air quality in residential buildings always threatens human health, such as sick building syndrome (SBS), respiratory diseases and low sleep quality. Although fresh air can dilute the concentration of air pollution, the widely used natural ventilation is uncontrolled and its ventilation rate is usually insufficient. Even in the indoor environments of residential buildings where the mechanical ventilation system is installed, different forms of ventilation systems have their unique problems. To create a healthy indoor environment, this investigation proposed a novel push-relay-pull mechanical ventilation system (fresh air supplying system) achieved by combining the mechanical air supply system (push), intermediate relay system (relay) and mechanical exhaust system (pull). This investigation further quantitatively evaluated the performance of the proposed system by comparing it with the traditional mechanical fresh air ventilation system using the age of air, infection risk and carbon dioxide (CO2) concentration indexes. The proposed system only needs to install one set of ducts as the traditional mechanical ventilation systems. It can ensure that all rooms would maintain good air quality, and also prevent the spread of pollutants, reduce the average infection risk of people inside a residential building and are conducive to epidemic prevention and control.
“…Note that the remaining fresh air (30 m 3 /h) is reserved for the living room as shown in Figure 4(b). In system III, since the exhaust valves (E1, E2, E3 and E4) of the four bedrooms are open in turn, the mechanical exhaust system forms a negative pressure 42 in the bedroom with the exhaust valves open, while the other bedrooms are under normal pressure. For example, Figures 3(c) and (d) show the ventilation mode of system III in stage A and stage B as shown in Figure 4(c), respectively.Figure 3.Working conditions of different ventilation units under different ventilation modes: (a) system I with simultaneous replacement mode; (b) system II with simultaneous replacement mode; (c) system III in stage A and (d) system III in stage B.Figure 4.Operation mode of fresh air system under different ventilation systems: (a) system I with simultaneous replacement mode; (b) system II with simultaneous replacement mode and (c) system III with sequential replacement mode (t1 represents the time of each period).…”
Section: Methodsmentioning
confidence: 99%
“…Note that the remaining fresh air (30 m 3 /h) is reserved for the living room as shown in Figure 4(b). In system III, since the exhaust valves (E1, E2, E3 and E4) of the four bedrooms are open in turn, the mechanical exhaust system forms a negative pressure 42 in the bedroom with the exhaust valves open, while the other bedrooms are under normal pressure. For example, Figures 3(c) and (d) show the ventilation mode of system III in stage A and stage B as shown in Figure 4(c), respectively.…”
Section: Novel Type Of Indoor Fresh Air Ventilation Systemmentioning
Poor indoor air quality in residential buildings always threatens human health, such as sick building syndrome (SBS), respiratory diseases and low sleep quality. Although fresh air can dilute the concentration of air pollution, the widely used natural ventilation is uncontrolled and its ventilation rate is usually insufficient. Even in the indoor environments of residential buildings where the mechanical ventilation system is installed, different forms of ventilation systems have their unique problems. To create a healthy indoor environment, this investigation proposed a novel push-relay-pull mechanical ventilation system (fresh air supplying system) achieved by combining the mechanical air supply system (push), intermediate relay system (relay) and mechanical exhaust system (pull). This investigation further quantitatively evaluated the performance of the proposed system by comparing it with the traditional mechanical fresh air ventilation system using the age of air, infection risk and carbon dioxide (CO2) concentration indexes. The proposed system only needs to install one set of ducts as the traditional mechanical ventilation systems. It can ensure that all rooms would maintain good air quality, and also prevent the spread of pollutants, reduce the average infection risk of people inside a residential building and are conducive to epidemic prevention and control.
“…Inhalation of aerosol particles suspended in the air or contact with contaminated surfaces could increase the risk of cross-infection. [2][3][4][5] As the 1 School of Electric Power, South China University of Technology, Guangzhou, China 2 demand for treating such patients has increased dramatically, some hospitals are facing greater pressure on their operations and medical resource allocation. If patients are kept in a general ward, the virus-carrying bioaerosols they inhale might leak outside via gaps in doors and other openings, infecting others outside the ward.…”
The high concentration of viral bioaerosols within the negative pressure isolation wards could pose a challenge to preventing potential cross-infection amongst healthcare workers (HCWs) and patients. Using the Euler–Lagrange methodology, this study numerically simulated the spatial and temporal distribution characteristics of bioaerosols in a typical negative pressure isolation ward as well as determined the interaction of ventilation mode and patient posture on ward ventilation performance. The removal effect of particle groups produced by two respiratory behaviours (breathing and coughing) was quantitatively analyzed, and the effect of exhaust air ratio and air exchange rate on particle distribution was discussed. The results showed that the migration characteristics of bioaerosol particles were sensitive to both the ventilation pattern and patient posture, which showed significant interactions. On this basis, the ventilation pattern with the best ventilation performance was evaluated, showing a particle removal effect of 70–85%. Due to the initial momentum difference, the diffusion behaviour of cough and breath particles was not consistent, but optimizing the airflow distribution near the exhaust outlet could improve their removal efficiency in the meantime. Further studies found that equal exhaust air velocity ratio facilitated the removal of aerosol particles, and an appropriate increase in the air exchange rate could also reduce the particle content.
“…The fate of airborne bacteria and viruses in negatively pressurized indoor spaces was investigated, 19 , 20 the larger number of air change rates in negatively pressurized indoor spaces was reported could lower the concentration of bacteria and viruses.…”
Ceiling fans are the ubiquitously used electrical appliance in indoor spaces that affect the local airflow pattern and, consequently, transmission of airborne pathogens and respiratory droplets. This study numerically investigated the effect of airflow induced by the ceiling fan and ventilation rate on aerosol distribution to mitigate exposure to airborne pathogens and COVID-19. A full-scale room with a ceiling fan, natural ventilation and an occupant was modelled through transient computational fluid-particle dynamics (CFPD). To analyze the relationship between the ceiling fan rotation speed and the aerosol distribution, a ceiling fan was operated with 160, 265 and 365 revolutions per minute (RPM). The effect of the ceiling fan on particles was analyzed for particles of different sizes. The increasing ceiling fan rotation speed, the percentage deposition of the aerosol particles with diameters >40 μm was increased. The effect of different ventilation rates on aerosol distribution was evaluated. The increased ventilation rate, the percentage of the total aerosol particles flushed out was increased. The effectiveness of the mask in mitigating the exposure risk of airborne pathogens was also investigated. In combination with the natural ventilation and mask, the ceiling fan was demonstrated to have the potential to reduce airborne pathogen transmission in indoor spaces.
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