Is opening windows in winter really the answer? Countering Covid’s Airborne Spread

Are you working in hat, gloves and scarf today – windows flung open to increase ventilation and counter the spread of Covid? It’s a nonsensical image, but seemingly one that governments across Europe are comfortable with.

In Germany, the government has introduced a ventilation drive to reduce the spread of the virus. Funds have been made available for air ventilation systems, but advice is also to open windows wide. Indeed, in recent guidance directed at the education sector, the German Environment Agency (UDA) stated that: “Our core recommendation is to air classrooms regularly every 20 minutes for about five minutes with windows wide open.”

Statements relating to ventilation here in the UK have been less overt, but the recommendation to open windows is still there. Again, in reference to the re-opening of schools, the website states: “…in cooler weather windows should be opened just enough to provide constant background ventilation, and opened more fully during breaks to purge the air in the space. Opening internal doors can also assist with creating a throughput of air.”

Is opening windows in winter really a sensible response? Of course not, particularly when proven alternatives are out there.

The virus is spread in three main ways: small droplets from speaking or coughing; via contaminated surfaces; and transmission by aerosols – the inhalation of invisible particles exhaled by an infected person.

Without ventilation, aerosols remain suspended in the air and become increasingly dense as time passes. It doesn’t take much for these particles to be released – simply breathing can be enough and they can escape from an improperly worn face mask. Scientists have shown that aerosols can infect people who spend more than a few minutes within a five-meter radius of an infected person, depending on the length of time and the nature of the interaction. 

Air ventilation units will move air around and refresh the room. But it is air sterilisation units that are really solving the aerosol problem. Put simply, these sterilisation units suck air in and expose the air to UV-C light which disinfects it before it is pushed out as clean air. The real benefit of these Covid-busting devices is that they can be used at the same time as rooms are occupied (high-powered UV-C lamps require people to vacate before they can be safely used).

Already, air sterilisation units are being used in staff-rooms, in veterinary practices and in spaces such as gyms and recording studios. These are relatively inexpensive devices, and there is typically a quick financial pay-back simply because installation can enable a business to re-open and operate safely with some semblance of normality again. Many users have invested as a direct result of Covid, but all will benefit from long-term use of these units because they will be equally effective in sterilising air from more regular winter cold and flu bugs. And should any new Covid strains develop (as has already happened in Denmark), having an air sterilisation unit installed will help to keep subsequent disruption to a minimum.

When advice from the top is to keep windows open throughout winter it is little wonder that businesses have turned to other solutions. Steering our way through these challenging times is hard enough – we shouldn’t have to be shivering as we do it. Air sterilisation is enabling forward-thinking business to keep windows shut, to keep warm, and – most importantly of all – to keep safe.


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