REMARK: This Q&A was part of the AIVC special COVID-19 newsletter published in July 2021. To subscribe to the newsletter please click here.

Opening windows almost always reduces the risk of contamination with SARS-CoV-2. But it is important to be aware of low outdoor air temperatures that could affect the comfort of occupants and exacerbate related health problems. 

However, the quantity of ventilation needed depends on the amount and nature of the SARS‐CoV‐2 aerosols. If the emission characteristics of SARS‐CoV‐2 and the dose‐ response curve was known, then it would be possible to calculate the ventilation rate needed to prevent occupants’ exposures exceeding a predefined safe dose. At the time of writing there is insufficient scientific knowledge to define this rate. 

It is advisable to open windows in one façade and keep the internal doors closed to minimise the risk of spreading SARS-CoV-2 to connected spaces, such as corridors or hallways. An exception should be made for classrooms where openable windows are located in two opposite facades. Then, windows can be opened in both facades with internal doors closed.


Willem de Gids, VentGuide