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Background Several studies indicate that coronavirus disease 2019 (COVID-19) is primarily transmitted within indoor spaces. Therefore, environmental characterization of severe acute respiratory syndrome coronavirus 2 viral load with respect to human activity, building parameters, and environmental mitigation strategies is critical to combat disease transmission. Methods We recruited 11 participants diagnosed with COVID-19 to individually occupy a controlled chamber and conduct specified physical activities under a range of environmental conditions; we collected human and environmental samples over a period of 3 days for each participant. Results Here we show that increased viral load, measured by lower RNA cycle threshold (CT) values, in nasal samples is associated with higher viral loads in environmental aerosols and on surfaces captured in both the near field (1.2 m) and far field (3.5 m). We also found that aerosol viral load in far field is correlated with the number of particles within the range of 1–2.5 µm. Furthermore, we found that increased ventilation and filtration significantly reduced aerosol and surface viral loads, while higher relative humidity resulted in lower aerosol and higher surface viral load, consistent with an increased rate of particle deposition at higher relative humidity. Data from near field aerosol trials with high expiratory activities suggest that respiratory particles of smaller sizes (0.3–1 µm) best characterize the variance of near field aerosol viral load. Conclusions Our findings indicate that building operation practices such as ventilation, filtration, and humidification substantially reduce the environmental aerosol viral load and therefore inhalation dose, and should be prioritized to improve building health and safety. [ABSTRACT FROM AUTHOR]

Synthesis of architecture and nature is highly reputed as a sustainable approach to overcome dominant built environment challenges, such as indoor air pollution, occupant's health burden, mechanical ventilation energy consumption as well as the separation between people and nature in urban life. Plants have numerous benefits for indoor spaces, including bioremediation of air contaminants-which promotes the quality of indoor air, drops mechanical ventilation demand, and consequently reduces energy consumption. In this research, a Double Skin Facade (DSF) system is introduced, incorporating Azolla as a natural air purifier in order to absorb occupants' bio-effluent and also contribute to providing fresh air for indoor spaces. Moreover, the CO 2 reduction capacity of Azolla within the DSF as a natural air purifier and its subsequent effects on mechanical ventilation size and the heating/cooling loads is investigated. The challenge for developing the idea of simulating plants activities' effect through a quantitative method is there are no software or calculating methods that recognize plants as indoor "air purifiers", therefore, phytoremediation effects on HVAC operation and energy sector have been remained concealed so far. The novelty of this research is attributed to integrating Azolla fern-a hydroponic plant, into building's components for indoor air bioremediation and establishing a new assessment protocol for integrating greenery's effect on HVAC loop in which the performance of the DSF incorporating Azolla as a natural air purifier is evaluated through "Indoor Air Quality" and "Ventilation Rate" procedures, which are acknowledged as practical engineering methods for specifying air exchange demand through mechanical equipment. It is observed that within the VR procedure, DSF with Azolla aids in sequestering indoor CO2, while within the IAQ procedure it results in reducing the building's air exchange demand rate and consequentially, decrease the building's overall energy consumption. Furthermore, the cooling effect of employing Azolla as natural shading component within a DSF cavity is assessed through applying its latent heat capacity into façade thermal convection/conduction, versus aluminum blinds with the same size and spacings to computationally evaluate the thermal benefits of plants for mitigating cavity/interior spaces overheating. Results are presented demonstrating this effect on "Indoor Sensible Cooling Rates" in 4 different configurations. • 5 m 2 Azolla per person in a typical office would reduce fresh air ventilation demand by almost 30%. • Green façade system affects indoor air quality by 170 PPM reduction in indoor CO 2 concentration. • Green façade reduces amount of air exchange per hour demand from 9.8 to 8.2 (ach). • Greenery decreased 2647.272 W of cooling equipment energy demand. • Plant acted as blind which resulted in 600 KWH annual reduction in energy consumption in warm seasons. [ABSTRACT FROM AUTHOR]

The indoor environment is the primary location for the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), largely driven by respiratory particle accumulation in the air and increased connectivity between the individuals occupying indoor spaces. In this study, we aimed to track a cohort of subjects as they occupied a COVID-19 isolation dormitory to better understand the impact of subject and environmental viral load over time, symptoms, and room ventilation on the detectable viral load within a single room. We find that subject samples demonstrate a decrease in overall viral load over time, symptoms significantly impact environmental viral load, and we provide the first real-world evidence for decreased aerosol SARS-CoV-2 load with increasing ventilation, both from mechanical and window sources. These results may guide environmental viral surveillance strategies and be used to better control the spread of SARS-CoV-2 within built environments and better protect those caring for individuals with COVID-19. [ABSTRACT FROM AUTHOR]