Buildings

14 pages, 5526 KiB

Open AccessArticle

Application of Portable Air Purifiers for Mitigating COVID-19 in Large Public Spaces

by Zhiqiang (John) Zhai, He Li, Robert Bahl and Keith Trace

Buildings 2021, 11(8), 329; https://doi.org/10.3390/buildings11080329 - 29 Jul 2021

Cited by 20 | Viewed by 9096

This study investigated, using validated computational fluid dynamics techniques, the actual performance of portable air purifiers for reducing the infection risks of airborne respiratory diseases such as COVID-19, by properly installing air purifiers in complicated large public spaces of primary concern, such as [...] Read more.

This study investigated, using validated computational fluid dynamics techniques, the actual performance of portable air purifiers for reducing the infection risks of airborne respiratory diseases such as COVID-19, by properly installing air purifiers in complicated large public spaces of primary concern, such as restaurants and ballrooms. The research results reveal that portable air purifiers with HEPA filtration provide an effective solution to help mitigate virus-carrying particles/droplets in large spaces where the central air conditioning system with HEPA filtration may not provide adequate dilution and/or effective ventilation. Deploying portable air purifier changes the local flow directions, and thus, reduces the cross-table airflows that may enhance the possibility of cross-infection. A field experiment was further conducted in a restaurant and a ballroom to verify the on-site performance. This study indicates that each space is unique in furniture, occupant and system layouts and capacities, and thus, requires individualized investigation of appropriate purifier number, capacities, and locations. Flexible solutions such as portable air purifiers are important and low-cost supplements to more elaborate solutions installed in central air systems. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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19 pages, 8473 KiB

Open AccessArticle

Numerical Investigation of Bioaerosol Transport in a Compact Lavatory

by Jingyuan Wan, Jianjian Wei, Yingtien Lin and Tengfei (Tim) Zhang

Buildings 2021, 11(11), 526; https://doi.org/10.3390/buildings11110526 - 08 Nov 2021

Cited by 13 | Viewed by 2305

Abstract

The lavatory is a fertile area for the transmission of infectious disease through bioaerosols between its users. In this study, we built a generic compact lavatory model with a vacuum toilet, and computational fluid dynamics (CFD) is used to evaluate the effects of [...] Read more.

The lavatory is a fertile area for the transmission of infectious disease through bioaerosols between its users. In this study, we built a generic compact lavatory model with a vacuum toilet, and computational fluid dynamics (CFD) is used to evaluate the effects of ventilation and user behaviors on the airflow patterns, and the resulting fates of bioaerosols. Fecal aerosols are readily released into the lavatory during toilet flush. Their concentration rapidly decays in the first 20 s after flushing by deposition or dilution. It takes about 315 s to 348 s for fine bioaerosols (<10 µm in diameter) to decrease to 5% of the initial concentration, while it takes 50 and 100 µm bioaerosols approximately 11 and <1 s, respectively, to completely deposit. The most contaminated surfaces by aerosol deposition include the toilet seat, the bowl, and the nearby walls. The 10 µm aerosols tend to deposit on horizontal surfaces, while the 50 and 100 µm bioaerosols almost always deposit on the bowl. In the presence of a standing thermal manikin, the rising thermal plume alters the flow field and more bioaerosols are carried out from the toilet; a large fraction of aerosols deposit on the manikin’s legs. The respiratory droplets generated by a seated coughing manikin tend to deposit on the floor, legs, and feet of the manikin. In summary, this study reveals the bioaerosol dilution time and the easily contaminated surfaces in a compact lavatory, which will aid the development of control measures against infectious diseases. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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17 pages, 4875 KiB

Open AccessFeature PaperArticle

Ventilation Strategies for Mitigation of Infection Disease Transmission in an Indoor Environment: A Case Study in Office

by Chen Ren, Hao-Cheng Zhu and Shi-Jie Cao

Buildings 2022, 12(2), 180; https://doi.org/10.3390/buildings12020180 - 04 Feb 2022

Cited by 24 | Viewed by 4888

Abstract

During the normalization phase of the COVID-19 epidemic, society has gradually reverted to using building space, especially for public buildings, e.g., offices. Prevention of airborne pollutants has emerged as a major challenge. Ventilation strategies can contribute to mitigating the spread of airborne disease [...] Read more.

During the normalization phase of the COVID-19 epidemic, society has gradually reverted to using building space, especially for public buildings, e.g., offices. Prevention of airborne pollutants has emerged as a major challenge. Ventilation strategies can contribute to mitigating the spread of airborne disease in an indoor environment, including increasing supply air rate, modifying ventilation mode, etc. The larger ventilation rate can inevitably lead to high energy consumption, which may be also ineffective in reducing infection risk. As a critical factor affecting the spread of viral contaminant, the potential of ventilation modes for control of COVID-19 should be explored. This study compared several ventilation strategies in the office, including mixing ventilation (MV), zone ventilation (ZV), stratum ventilation (SV) and displacement ventilation (DV), through analyzing ventilation performance and infection risk for the optimal one. By using ANSYS Fluent, the distributions of airflow and pollutant were simulated under various ventilation modes and infected occupants. The SV showed greater performance in mitigating infection disease spread than MV, ZV and DV, with an air distribution performance index (ADPI) of 90.5% and minimum infection risk of 13%. This work can provide a reference for development of ventilation strategies in public space oriented the prevention of COVID-19. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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24 pages, 12240 KiB

Open AccessArticle

Exposure Risk to Medical Staff in a Nasopharyngeal Swab Sampling Cabin under Four Different Ventilation Strategies

by Jianchao Ma, Hua Qian, Fan Liu, Guodong Sui and Xiaohong Zheng

Buildings 2022, 12(3), 353; https://doi.org/10.3390/buildings12030353 - 15 Mar 2022

Cited by 3 | Viewed by 1740

Abstract

Medical staff working in a nasopharyngeal swab sampling cabin are exposed to a higher exposure risk of COVID-19. In this study, computational fluid dynamics (CFD) are used to evaluate the exposure risk to medical staff in a nasopharyngeal swab sampling cabin of Chinese [...] Read more.

Medical staff working in a nasopharyngeal swab sampling cabin are exposed to a higher exposure risk of COVID-19. In this study, computational fluid dynamics (CFD) are used to evaluate the exposure risk to medical staff in a nasopharyngeal swab sampling cabin of Chinese customs under four different ventilation strategies, i.e., multiple supply fans ventilation (MSFV), multiple exhaust fans ventilation (MEFV), single exhaust fan and outer windows closed ventilation (SEFV), and single exhaust fan and outer windows opened ventilation (SEFV-W). The impact of physical partitions on exposure risk is also discussed. The results show that MSFV performed best in reducing exposure risk. No significant difference was found between MEFV and SEFV. SEFV-W performed better than SEFV with a ventilation rate of 10–50 L/(s∙Person), while it performed worse with a ventilation rate of 50–90 L/(s∙Person). The exposure risk to medical staff did not decrease linearly with the increase in the ventilation flow rate under the four ventilation strategies. For MSFV, the installation of partitions is conducive to the reduction in the exposure risk. This study is expected to provide some guidance for ventilation designs in sampling cabins. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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18 pages, 4428 KiB

Open AccessArticle

Human Close Contact Behavior-Based Interventions for COVID-19 Transmission

by Doudou Miao and Nan Zhang

Buildings 2022, 12(3), 365; https://doi.org/10.3390/buildings12030365 - 16 Mar 2022

Cited by 6 | Viewed by 2817

Abstract

COVID-19 has threatened human lives. Countries have implemented various interventions such as vaccination, mask-wearing, body temperature screening, and isolation. However, the effectiveness of single and combined interventions has not yet been accurately analyzed. In this study, an improved SEIR model considering both real [...] Read more.

COVID-19 has threatened human lives. Countries have implemented various interventions such as vaccination, mask-wearing, body temperature screening, and isolation. However, the effectiveness of single and combined interventions has not yet been accurately analyzed. In this study, an improved SEIR model considering both real human indoor close contact behaviors and susceptibility to COVID-19 was established. Taking Hong Kong as an example, a quantitative assessment of the relationship between the efficiency of single and combined interventions and implementation time and intensity was carried out. The results showed that the infection risk (one-hour close contact with an infected person) of COVID-19 of students, workers, and non-workers/non-students was 3.1%, 8.7%, and 13.6%, respectively. Workplace closures were more effective among built environment interventions. If mask-wearing was mandatorily required in schools, workplaces, supermarkets, shopping centers, and public transport, COVID-19 could not be totally restricted. Workers should be prioritized for vaccination, followed by non-workers/non-students and students. Among all interventions, reducing close contact rate and increasing vaccination rate were better interventions. There was no COVID-19 outbreak (basic reproduction number R₀ = 1) if the close contact reduction rate was 59.9% or the vaccination rate reached 89.5%. The results may provide scientific support for COVID-19 prevention and control. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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14 pages, 5883 KiB

Open AccessArticle

Sneezing Aerosol Transport in an Indoor Farmers’ Market

by Jiawei Deng and Feng Yao

Buildings 2022, 12(3), 355; https://doi.org/10.3390/buildings12030355 - 15 Mar 2022

Cited by 1 | Viewed by 1834

Abstract

The transportation and surface deposition of aerosols from sneezing in a small indoor farmers’ market are studied numerically. The effects of numbers and locations of the entrances and exits of the market are discussed under the condition of natural convection. The results indicate [...] Read more.

The transportation and surface deposition of aerosols from sneezing in a small indoor farmers’ market are studied numerically. The effects of numbers and locations of the entrances and exits of the market are discussed under the condition of natural convection. The results indicate that aerosols leave the indoor environment more quickly when two doors are designed face to face on the walls perpendicular to the natural wind direction compared to other natural ventilation strategies. The concentrations of aerosols accumulated on the surfaces of the stalls and human bodies inside the market are also lower. In this case, the risk of contacting the virus is relatively low among susceptible individuals in the indoor farmers’ markets. Moreover, opening more doors on the walls parallel to the natural wind direction is not beneficial for the fast exhaust of aerosols. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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14 pages, 3053 KiB

Open AccessArticle

A Modified Surgical Face Mask to Improve Protection and Wearing Comfort

by Tengfei (Tim) Zhang, Tinglu Zhang and Sumei Liu

Buildings 2022, 12(5), 663; https://doi.org/10.3390/buildings12050663 - 17 May 2022

Cited by 5 | Viewed by 2166

Abstract

Wearing face masks is essential for reducing infection during the COVID-19 pandemic. However, ordinary surgical face masks can provide only moderate protection. The N95 face masks should provide sufficient protection but may impose complaints about breathing difficulty or even impair respiratory health. This [...] Read more.

Wearing face masks is essential for reducing infection during the COVID-19 pandemic. However, ordinary surgical face masks can provide only moderate protection. The N95 face masks should provide sufficient protection but may impose complaints about breathing difficulty or even impair respiratory health. This investigation proposed a novel face mask modified from the surgical face mask to improve both protection and comfort. The filter material of the surgical face mask was covered and sealed on a cardboard support frame but with openings for air permeating through. The modified face masks were worn by a test subject for measuring the air contents inside the face masks. The protection performance was evaluated by the overall PM₁ filtration efficiency. The concentrations of CO₂, O₂, N₂, and water vapor were adopted to evaluate the breathing comfort. The performance of the proposed face mask was compared with the market-available surgical and N95 face masks. In addition, CFD modeling was adopted to investigate the dynamic air exchange of the face mask with respiration and the surrounding air. Impacts of the air sampling tube positions on the measurement results were also examined. The results revealed that the overall PM₁ filtration efficiency of the modified face mask could reach 96.2%, which was much higher than that of the surgical face mask and only slightly lower than the N95 face mask. As compared with the N95 face mask, the modified mask reduced the respiratory flow resistance and the concentrations of CO₂ and water vapor and thus increased the O₂ content and breathing comfort. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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45 pages, 6810 KiB

Open AccessArticle

Improving the Effectiveness of Anti-COVID Measures in Buildings: Learning from Users’ Perception

by Elisa Zatta, Massimiliano Condotta, Valeria Tatano, Alice Bettelli, Elena Zanella, Nicola La Magna and Luciano Gamberini

Buildings 2022, 12(8), 1161; https://doi.org/10.3390/buildings12081161 - 03 Aug 2022

Cited by 1 | Viewed by 1233

Abstract

The COVID-19 spread abruptly changed the fruition of indoor environments, where necessary adaptive measures have since been implemented. Buildings open to the public were suddenly equipped with physical devices aiming to encourage users’ appropriate behaviors, such as hand sanitizing, social distancing, and temperature [...] Read more.

The COVID-19 spread abruptly changed the fruition of indoor environments, where necessary adaptive measures have since been implemented. Buildings open to the public were suddenly equipped with physical devices aiming to encourage users’ appropriate behaviors, such as hand sanitizing, social distancing, and temperature monitoring. Through a twofold architectural-psychological perspective, the paper presents a research aiming to understand how users perceive these devices in the Italian context and to identify the design features that could improve their effectiveness in enhancing individuals’ awareness. With an interdisciplinary approach, four methods were adopted: observational field surveys, background and normative framework analysis, survey research through an online questionnaire, and case studies survey research. The results confirm the overall effectiveness of the implemented anti-COVID strategies, their suitability in encouraging individuals’ appropriate behaviors, and the importance of regulating the users’ flow indoors. The research allowed defining the devices (hand-sanitizing devices and temperature-measurement instruments) and wayfinding systems more suited to be included in the prevention strategy and identified their more appropriate design features in relation to the users’ feedback. Operational suggestions are presented as well. The adopted experimental approach can be useful in supporting decision making in managing of the built environment in both the current and future contexts. Full article

(This article belongs to the Special Issue Toward Immune Buildings: Lessons Learned from the COVID-19 Pandemic and Its Aftermath)

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