Intended for healthcare professionals

Letters Covid-19: controlling airborne transmission

Open the windows? It’s not that easy

BMJ 2022; 376 doi: (Published 17 January 2022) Cite this as: BMJ 2022;376:o35
  1. Colin W Brown, research student, former GP
  1. Glasgow, UK
  1. colin.brown{at}

Dancer and colleagues’ editorial is a valuable commentary on implementing controls for the airborne transmission of SARS-CoV-2.1 As they say, adding “ventilation” to policy documents is not enough: procedures are required, customised by each organisation and presented clearly for people who might not understand the aerodynamic behaviours of aerosols now known to be lethally infectious.

Window opening, for example, is generally understood and seems quick to do. But the window and door patterns and timings required for air exchange are specific to each room, 2 including how to use its heating system to restore comfort after repeated five or 10 minute ventilation periods and how to manage occupancy.2345

The role of carbon dioxide monitors in managing shared air, and the use of air filtration when ventilation cannot be improved, also require engineering based procedures at the individual room scale. Such procedures cannot be left to end users’ experiments. Expertise lies with the heating, ventilation, and air conditioning industry, but business forces have failed to implement it so far on the scale required.

Transforming ventilation policy into hundreds of standard procedures fit to implement in millions of rooms requires national direction. This crosses government departments, so new organisations may be needed, as if we were at war. We are.


  • Competing interests: None declared.

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