Virus Tool

The Indoor Scenario Simulator for COVID-19 was developed with financial support from the State Secretariat for Economic Affairs SECO ( and in cooperation with Christian Monn, SECO.

This tool calculates the concentration of viruses in a room with perfect mixing for one or more people who emit viruses while breathing normally, speaking softly or loudly. The percentiles of the distribution of viral viral emission levels in the adult population were modelled based on published figures of virus copies (determined by PCR, polymerase chain reaction) and aerosol emissions.

The tool allows the calculation of scenarios where virus carriers enter a room, stay there for a certain time, and what this means for exposure and inhaled dose from other people in the room.

A detailed description of the tool can be found in the blog. The underlying scientific article can be found in the scientific magazine Aerosol and Air Quality Research.

This tool was created with great care and checked in detail, but may contain errors. DO NOT use the tool as the sole element for critical decisions.

Download (English)

Runterladen (Deutsch)

Télécharger (Français)

Scarica (Italiano)

免費下載 (正體中文版)

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ダウンロード (日本語版)

The tool is free of charge and made available under the Creatives Commons Attribution License 4.0 (CC BY 4.0).


Guide towards healthy classrooms

This tool provides guidance on how to assess and define ventilation strategies to reduce the potential spread of the SARS-CoV-2 virus through aerosol transmission in classrooms.

The guide explains how to check if the ventilation is sufficient to reduce the risk of transmission by aerosols. We use CO2 as a tracer gas since this is already emitted by the people in the room. 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 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.

This guide was developed by researchers from Europe’s COST-Action INDAIRPOLLNET (led by Xavier Querol and Maricruz Minguillón from CSICand Michael Riediker from SCOEH).

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


  1. The guide (PDF)
  2. 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.

The guide is free of charge and comes without a specific license. Feel free to copy it into your language. Please attribute the source and the work of INDAIRPOLLNET when using it.