How can we reduce the potential spread of the SARS-CoV-2 virus through aerosol transmission in  classrooms? Researchers from Europe’s COST-Action INDAIRPOLLNET (led by Xavier Querol and Maricruz Minguillón from CSIC and Michael Riediker from SCOEH) developed a guide that provides strategies and possible solutions.

The guide focuses on ventilation in classrooms, alongside tools to evaluate the implemented ventilation strategies. The use of masks, maintaining physical distance, and upholding hygiene measures, must be adhered to in conjunction with the strategies described in the guide.

The guide explains how to check if the ventilation is sufficient to reduce the risk of transmission by aerosols. For this we use CO2 as a tracer. The guide also describes the risk of infection under different scenarios in a classroom. 

The guide can be applied to other types of indoor spaces, such as offices or other public buildings, though some adjustments may be needed for physical characteristics (e.g. area and volume). 

The measures described aim to reduce the risk of contagion, but they do not eliminate the risk entirely.


  1. The guide (PDF)
  2. A Spreadsheet File (Excel) to calculate how well a room is ventilated (requires CO2-measurements)
  3. The Indoor Scenario Simulator

The guide is also available at CSIC.

P.S. This guide is useful also for classrooms with small kids. While small kids do not seem to be good spreaders of the disease (and thus may not need to wear masks), they still need to be protected from older virus emitters, and they still should follow fundamental hygiene rules.

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