Ventilation regimes of school classrooms against airborne transmission of infectious respiratory droplets: A review

Abstract

Airborne transmission of small respiratory droplets (i.e., aerosols) is one of the dominant transmission routes of pathogens of several contagious respiratory diseases, which mainly takes place between occupants when sharing indoor spaces. The important role of ventilation in airborne infection control has been extensively discussed in previous studies, yet little attention was paid to the situation in school classrooms, where children spend long hours every day. A literature study was conducted to identify the existing ventilation strategies of school classrooms, to assess their adequacy of minimizing infectious aerosols, and to seek further improvement. It is concluded that school classrooms are usually equipped with natural ventilation or mixing mechanical ventilation, which are not fully capable to deal with both long-range and short-range airborne transmissions. In general, the required ventilation designs, including both ventilation rates and air distribution patterns, are still unclear. Current standards and guidelines of ventilation in school classrooms mainly focus on perceived air quality, while the available ventilation in many schools already fail to meet those criteria, leading to poor indoor air quality (IAQ). New ways of ventilation are needed in school classrooms, where the design should be shifted from comfort-based to health-based. Personalized ventilation systems have shown the potential in protecting occupants from aerosols generated within short-range contact and improving local IAQ, which can be used to compensate the existing ventilation regimes. However, more studies are still needed before such new ventilation methods can be applied to children in school classrooms.

Adaptive school grounds design in response to COVID-19: Findings from six primary schools in South East England

“…Because the majority of studies on architecture/design and COVID-19 in schools have focused on within buildings [ [41] , [42] , [43] ], our research, which focuses on a very original topic, is difficult to compare with the current peer-review literature, which unfortunately does not address the resilient design of school playgrounds. However, at the time of writing this article, our findings are consistent with Waite's article published in an architectural magazine [ 44 ].…”

Alternative Covid-19 mitigation measures in school classrooms: analysis using an agent-based model of SARS-CoV-2 transmission

“…This concept has gained currency as evidence emerges for transmission in settings which require long distance transport of fine aerosols, away from an infected source, as recently summarized in [1]. The specific principles and issues related to airborne transmission in classrooms and factors related to ventilation in schools have been reviewed by Ding et al (2022) [38]. Transmission and risk models have been developed [e.g., 37, 39, 40] which frame transmission risk in terms of long-range dispersal of aerosols within closed and open spaces.…”

“…Long-range and short-range exposure models to airborne aerosols are not mutually exclusive. Indeed, both kinds of process will occur concurrently in many settings [12, 38]. The question then is in what circumstances does one or the other become dominant?…”

“…However, the concentration will be very much less if there is ventilation. According to [38] a classroom of 30 children should have a room ventilation rate of at least 120 litres per minute, meaning that it would take only 20 minutes to replace the air in a classroom. Here the background concentration of infected aerosol would be approximately 10 −3 X.…”

Why don’t we just open the windows?

“…While keeping your distance, wearing a mask, and getting vaccinated have provided much protection, one intervention that would have a significant impact is adequate indoor ventilation. Healthcare, homes, schools, and workplaces should have been encouraged to improve ventilation at the very beginning of the pandemic, but tardy recognition of the airborne route by leading authorities in 2020 stalled any progress that could have been made at that stage 91011. This was compounded by controversies over the terms “droplet” and “aerosol,” as the definition of these dictates different infection prevention strategies, including type of mask 6…”