Natural ventilation strategy and related issues to prevent coronavirus disease 2019 (COVID-19) airborne transmission in a school building

Abstract

The World Health Organization (WHO) announced that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may spread through aerosols, so-called airborne transmission, especially in a poorly ventilated indoor environment. Ventilation protects the occupants against airborne transmission. Various studies have been performed on the importance of sufficient ventilation for diluting the concentration of virus and lowering any subsequent dose inhaled by the occupants. However, the ventilation situation can be problematic in public buildings and other shared spaces, such as shops, offices, schools, and restaurants. If ventilation is provided by opening windows, the outdoor airflow rate depends strongly on the specific local conditions (opening sizes, relative positions, climatic and weather conditions). This study uses field measurements to analyze the natural ventilation performance in a school building according to the window opening rates, positions, and weather conditions. The ventilation rates were calculated by the tracer gas decay method, and the infection risk was assessed using the Wells-Riley equation. Under cross-ventilation conditions, the average ventilation rates were measured at 6.51 h -1 for 15% window opening, and 11.20 h -1 for 30% window opening. For single-sided ventilation, the ventilation rates were reduced to about 30% of the values from the cross-ventilation cases. The infection probability is less than 1% in all cases when a mask is worn and more than 15% of the windows are open with cross-ventilation. With single-sided ventilation, if the exposure time is less than one hour, the infection probability can be kept less than 1% with a mask. However, the infection probability exceeds 1% in all cases where exposure time is greater than two hours, regardless of whether or not a mask is worn. Also, when the air conditioner was operated with a window opening ratio of 15%, power consumption increased by 10.2%.

Evaluation of airborne particle exposure for riding elevators

“…The aerosols released by infected individuals through sneezing, coughing, talking, and breathing could accumulate in the air over time, increasing in concentration, if the elevator is not well ventilated. Smaller virus-containing particles can remain suspended in the air over long distances and time periods [ [ 19 ]]. Nishiura et al, 2020 [ [ 20 ]] found that transmission of COVID-19 in a confined space was 18.7 times greater compared to an open-air environment.…”

Dental Education during the COVID-19 Pandemic in a German Dental Hospital

“…Large dental treatment rooms have shown certain effects in terms of bioaerosol distribution [ 28 ]. As proposed by several authors, cross ventilation using the opening of windows and air purification devices were shown to be highly effective methods to reduce the risk of airborne transmission of COVID virus containing particles [ 29 , 30 , 31 , 32 ]. The course room (326.2 sqm) in contrast is equipped with 20 windows in total, each measuring 4 sqm and thanks to the fact that they can be opened this allows a rapid ventilation of the complete course room.…”

Airflow deflectors of external windowsto induce ventilation: Towards COVID-19 prevention and control

“…On the other hand, mechanical ventilation systems may consume large amount of energy consumption (X. D. Cao, Dai, & Liu, 2016 ; Li, Shen, & Yu, 2017 ), which is not beneficial for the sustainable development of society. Thus, it is necessary to do research on the design of natural ventilation systems under the situation of epidemic prevention and control ( Corticos & Duarte, 2021 ; Park, Choi, Song, & Kim, 2021 ). Natural ventilation is a kind of passive green building technology using thermal pressure caused by the density difference of air inside and outside the building or the wind pressure caused by outdoor atmospheric movement to induce outdoor fresh air ( Gautam, Rong, Zhang, & Abkar, 2019 ; Moey, Chan, Tai, Go, & Chong, 2021 ).…”