The Influence of Ventilation Measures on the Airborne Risk of Infection in Schools: A Scoping Review

Abstract

Objectives: To review the risk of airborne infections in schools and evaluate the effect of intervention measures reported in field studies. Background: Schools are part of a country’s critical infrastructure. Good infection prevention measures are essential for reducing the risk of infection in schools as much as possible, since these are places where many individuals spend a great deal of time together every weekday in a small area where airborne pathogens can spread quickly. Appropriate ventilation can reduce the indoor concentration of airborne pathogens and reduce the risk of infection. Methods: A systematic search of the literature was conducted in the databases Embase, MEDLINE, and ScienceDirect using keywords such as school, classroom, ventilation, carbon dioxide (CO2) concentration, SARS-CoV-2, and airborne transmission. The primary endpoint of the studies selected was the risk of airborne infection or CO2 concentration as a surrogate parameter. Studies were grouped according to the study type. Results: We identified 30 studies that met the inclusion criteria, six of them intervention studies. When specific ventilation strategies were lacking in schools being investigated, CO2 concentrations were often above the recommended maximum values. Improving ventilation lowered the CO2 concentration, resulting in a lower risk of airborne infections. Conclusions: The ventilation in many schools is not adequate to guarantee good indoor air quality. Ventilation is an important measure for reducing the risk of airborne infections in schools. The most important effect is to reduce the time of residence of pathogens in the classrooms.

Measuring Indoor Air Quality Does Not Prevent COVID-19

“…Peer-reviewed studies conducted in the past 2 years have evaluated the contribution of ventilation in schools to reducing COVID-19 transmission as a component of multilayered strategies. 18,[38][39][40][41] Buonanno et al 38 showed that mechanical ventilation installed in 56 Italian schools reduced infection risk by at least 74% compared to over 10,000 classrooms with only natural ventilation. A recent literature review reinforced this finding, defining a maximum acceptable average value for CO 2 of 1,000 ppm, which should be lowered to 800 ppm during a pandemic, using carbon dioxide as a surrogate for infection risk.…”

“…A recent literature review reinforced this finding, defining a maximum acceptable average value for CO 2 of 1,000 ppm, which should be lowered to 800 ppm during a pandemic, using carbon dioxide as a surrogate for infection risk. 41 The authors concluded that every classroom should have mechanical ventilation, which also prevents temperature extremes and improves students' abilities to concentrate. 41 A literature review by McLeod et al 40 suggested 1,000 ppm of CO 2 should never be exceeded over a teaching hour.…”

“…42 Portable air cleaners can reduce particles in the air, but do not replace mechanical ventilation in providing infection control. 40,41…”

“…42 Portable air cleaners can reduce particles in the air, but do not replace mechanical ventilation in providing infection control. 40,41 Industry standards have changed over the years. A review of 50 years of classroom air quality research concludes that natural ventilation is inadequate to meet schools' needs.…”

“…41 The authors concluded that every classroom should have mechanical ventilation, which also prevents temperature extremes and improves students' abilities to concentrate. 41 A literature review by McLeod et al 40 suggested 1,000 ppm of CO 2 should never be exceeded over a teaching hour. Another study demonstrated the importance of being able to directly observe CO 2 as a component of managing natural ventilation.…”