Tempo-spatial infection risk assessment of airborne virus via CO2 concentration field monitoring in built environment.

The aerosol transmission was academically recognized as a possible transmission route of Coronavirus disease 2019 (COVID-19). We established an approach to assess the indoor tempo-spatial airborne-disease infection risks through aerosol transmission via real-time CO2 field measurement and occupancy monitoring. Compared to former studies, the proposed method can evaluate real-time airborne disease infection risks through aerosol transmission routes. The approach was utilized in a university office. The accumulated infection risk was calculated for three occupants with practical working schedules (from occupancy recording) and one hypothesis occupant with a typical working schedule. COVID-19 was used as an example. Results demonstrated that the individual infection risks diversified with different dwell times and working places in the office. For the three occupants with a practical working schedule, their 3-day accumulated infection risks were respectively 0.050%, 0.035%, 0.027% and 0.041% due to 11.6, 9.0 and 13.8 h exposure with an initial infector percentage of 1%. The results demonstrate that location and dwell time are both important factors influencing the infection risk of certain occupant in built environment, whereas existing literature seldom took these two points into consideration simultaneously. On the contrary, our proposed approach treated the infection risks as place-by-place, time-by-time and person-by-person diversified in the built environment. The risk assessment results can provide early warning for building occupants and contribute to the transmission control of air-borne disease.

An agent-based study on the airborne transmission risk of infectious disease in a fever clinic during COVID-19 pandemic.

Prevention of nosocomial infections is particularly important for the control of COVID-19 pandemic. We conducted a field study and performed extensive numerical simulations of infection transmission in a fever clinic during pandemic through an agent-based model with pedestrian dynamic and an infection transmission model. Furthermore, we evaluated the cross-infection risk of the patients influenced by the patient inject flow, medical service capability and plane layout. The service capability of fever clinic is determined by the least efficient medical session. When patient inject flow exceeded the service capability, the average dwell time, contact time, exposure dose, and risk of infection of patients all increased dramatically. With the patient inject flow exceeding the service capability, the growth rate of the contact time between patients and the cross-infection risk increased by 11.5-fold and 29.5-fold, respectively. The plane layout of the fever clinic affected the exposure dose and risk of infection. The waiting areas in the fever clinic had the highest risk, where the cumulative exposure dose of virus occupied up to 66.5% of the total. Our research will help to evaluate the biosafety of hospital buildings used for the diagnosis and treatment of infectious diseases.

Correlations between the urban built environmental factors and the spatial distribution at the community level in the reported COVID-19 samples: A case study of Wuhan.

COVID-19 has dramatically changed the lifestyle of people, especially in urban environments. This paper investigated the variations of built environments that were measurably associated with the spread of COVID-19 in 150 Wuhan communities. The incidence rate in each community before and after the lockdown (January 23, 2020), as respective dependent variables, represented the situation under normal circumstances and non-pharmaceutical interventions (NPI). After controlling the population density, floor area ratio (FAR), property age and sociodemographic factors, the built environmental factors in two spatial dimensions, the 15-minute walking life circle and the 10-minute cycling life circle, were brought into the Hierarchical Linear Regression Model and the Ridge Regression Model. The results indicated that before lockdown, the number of markets and schools were positively associated with the incidence rate, while community population density and FAR were negatively associated with COVID-19 transmission. After lockdown, FAR, GDP, the number of hospitals (in the 15-minute walking life circle) and the bus stations (in the 10-minute cycling life circle) became negatively correlated with the incidence rate, while markets remained positive. This study effectively extends the discussions on the association between the urban built environment and the spread of COVID-19. Meanwhile, given the limitations of sociodemographic data sources, the conclusions of this study should be interpreted and applied with caution.

Field study to characterize customer flow and ventilation rates in retail buildings in Shenzhen, China.

Reduction of the customers' exposure risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the retail buildings, i.e., supermarkets and small shops where residents purchase daily necessities is of prime importance during pandemic. In this study, the main influencing factors of the exposure risk of SARS-CoV-2, namely the occupant density, dwell time, and fresh air volume per person, were on-sited measured in 5 supermarkets and 21 small shops in Shenzhen, China. The small shops with an occupant area per person of 4.7 m2/per presented a more crowded environment than the supermarkets with an occupant area per person of 18.8 m2/per. The average dwell time of customers in the supermarkets linearly increased with the floor area and its probability distribution was fitted well by the Gamma distribution with a shape parameter of 3.0. The average dwell time of customers in the supermarkets was relatively longer than the combination of five types of small shops. In addition, the measured average outdoor air change rate of the small shops by natural ventilation was 10.7 h-1, while that of the supermarkets by mechanical ventilation was only 0.7 h-1. Correspondingly, the CO2 concentration in the small shops was 100-150 ppm lower than the supermarkets. The small shops provided an average fresh air volume per person of 216 m3/(h·per), far exceeding the supermarkets with a value of 95 m3/(h·per).

A field study on indoor environment quality of Chinese inpatient buildings in a hot and humid region.

In this research, objective physical measurements and subjective questionnaire surveys are used to investigate the indoor environment quality of Chinese inpatient buildings. The relative humidity in the inpatient buildings reaches 65%-75% during summer, resulting in the regular appearance of microbial growth on indoor surfaces. The average outdoor air change rate measured through the CO2 concentration decay method in the sampled inpatient rooms is 1.1 h-1, which is 45% below the standard threshold. The CO2 concentration in over 99% of the functional spaces is below the threshold of 1000 ppm. However, the dissatisfaction rate of the air freshness is higher than 25%, owing to the characteristics of healthcare activities. Insufficient fresh air volume and high supply air humidity ratio of the outdoor air system result in the inadequate dehumidification capacity and the over-humid environment in the inpatient buildings. From the perspective of indoor TVOC and PM2.5 concentration, a hospitable IAQ is achieved in the inpatient buildings. In the nurse unit, the illumination levels in public areas, such as patient corridors and nurse stations, are inadequate. The average noise levels (A) in the inpatient rooms and nurse stations are 50.7 and 61.6 dB, respectively, which exceeds the Chinese standard. According to the subjective survey, the dissatisfaction rates of overall IEQ in the summer for patients and visitors are 7.9% and 10.4%, respectively, while for staff it is 34.8%. Statistical analysis reveals that the satisfaction levels of the patient with the IEQ are higher than that of the visitor and staff.

Energy performance of an innovative bifacial photovoltaic sunshade (BiPVS) under hot summer and warm winter climate.

The bi-facial photovoltaic sunshade (BiPVS) is an innovative solution that utilizes vertically mounted bi-facial photovoltaic modules to provide shading. The BiPVS is capable of converting incident solar radiation into electricity on both the front and rear sides of the module, resulting in higher electrical efficiency compared to traditional mono-facial PV sunshades. The BiPVS has great potential as a sustainable solution for building shading and energy generation, which allows for improved indoor light/thermal environment and building energy efficiency. In this study, the bi-facial photovoltaic sunshade (BiPVS) was implemented in an office under typical hot summer and warm winter climate of Shenzhen, China. The energy performance of the BiPVS was analyzed using Energyplus. The comprehensive building energy saving was evaluated by comparing the energy consumption of the office with and without the BiPVS. Results showed that the total annual photovoltaic power generation was 133.19 kWh, while the comprehensive building energy savings were 159.65 kWh. Additionally, carbon dioxide emissions were reduced by 83.29 kgCO2 per year. The proposed method can help optimize the design parameters of BiPVS according to specific climate conditions, building types, and orientation, and contribute to the development of high-efficiency BIPV technology and support efforts towards carbon neutrality.

Comparison of COVID-19 infection risks through aerosol transmission in supermarkets and small shops.

Aerosol transmission is academically recognized as possible transmission route of Coronavirus disease 2019 (COVID-19). We established an approach to assess the airborne-disease infection risks through aerosol transmission based on the dose-response model and aerosol transport model. The accuracy of evaluation was guaranteed with on-site surveyed ventilation rate and occupant behavior. With the proposed approach, COVID-19 infection risks in 5 typical supermarkets and 21 small shops were evaluated. With one original infected early-shift staff, the average aerosols concentrations at steady-state are 1.06 × 10-3 RNA copies/m3 in the supermarkets and 4.73 × 10-2 RNA copies/m3 in the small shops. With the assumption of 5% original infected staff in the retail buildings, the infection probability of one customer is 1.40 × 10-6 for visiting one small shop and 6.22 × 10-6 for visiting one supermarket. The averaged infection risk in the supermarkets is higher than the small shops (p-value<0.001). On the other hand, the infection risks are higher for the staff working with the infected staff compared with the customers. The proposed approach can be applied to other occupied buildings and assist the pandemic control policy making for sustainable cities and society.