Window Opening or Mechanical Ventilation Systems for Italian Schools? Energetic Aspects, CO2 Concentration and Infection Risk Assessment Based on the SARS-CoV-2 Data

During the first COVID outbreak, schools were seen as a substantial issue regarding the spread of the disease, since schools are the most densely occupied indoor environment continuously over time. The infection risk of SARS-CoV-2 could reach large levels, especially in locations with inadequate ventilation rates, according to the current knowledge of airborne transmitted diseases. The first main drive to reduce viral concentration is dilution, provided by infiltration, air change through aeration (window opening), mechanical ventilation; the second drive is filtration. After a brief investigation of the prescriptions and requirements for ventilation in school rooms stipulated by Italian law, the present work compares the energy requirements for ventilation in two main cases—window opening (and infiltration) and mechanical ventilation—the effect of wearing or not wearing a mask is also considered. Afterward, the focus is shifted to the infection risk assessment, comparing the two different ventilation techniques as mentioned above. Not only is it found that window opening is far from an effective technique for controlling the spread of the disease; it is also found that for the same amount of thermal energy needed, mechanical ventilation can reduce the individual infection risk by a factor of 3, thus providing a better IAQ. It is also proved that mechanical ventilation, in terms of infection control, can not only replace but even outperform the effect of masks.

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