The benefits of ventilation are greatest in rooms where people spend more time together (>30 min).

In many buildings the air distribution in rooms is poor, and stagnant spaces may create zones of higher risk.

There is evidence from several studies that air movement happens between rooms, and this can result in transmission between rooms Visualising SARS-CoV-2 transmission routes and mitigations | The BMJ.

You should consider ventilation in all spaces in a building, not just a small number of rooms. The use of air cleaners may help to reduce both transmission within the same room and between rooms. 

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