Why Proper Ventilation Has Never Been So Important

Corona Schutz Lüften

It is always good to open a window from time to time. But now there is ample evidence that it can greatly reduce the chance of contracting diseases, including COVID-19.

Who knew that letting in a bit of fresh air could possibly save your life?

What happens when you don’t open the window

Proper ventilation has the ability to keep out bacteria and other microorganisms that may be harmful to our health, as well as reduce the amount of moisture in the air. Indoor spaces with high amounts of air humidity can provide the perfect environment for bacteria to grow. If you can limit the amount of moisture in the air, you help curb the growth of bacteria and mold as well.

Research shows that air movement within a room can affect how a disease spreads. Stale, old air can help viruses duplicate, especially when given a humid environment. Breathing in these viruses and bacteria can help spread coughs, colds, tuberculosis and other illnesses -- including COVID-19.

Even worse, others can be infected by airborne viruses even though the infected person has already left the room. Aerosol can also linger in the air for quite some time, because the particles are so light, they essentially stay afloat in the room. This can lead to indirect infections -- the person carrying the virus has already left the room, but his or her aerosol has not, infecting those that enter the environment.

Thankfully, smart home can warn you when your indoor air quality is getting compromised. A quick notification on your phone can remind you when you need to let in some fresh air.

Aerosol in air

Why is this important?

When someone coughs, sneezes, or even speaks, they breathe out aerosole, tiny water droplets that float through the air. These droplets, which can carry infectious diseases, can spread quickly throughout a room, especially indoors or in enclosed spaces.

In enclosed spaces, the number of pathogens in the room air can increase over time. Regular ventilation reduces the number of fine droplets containing pathogens in the air and thus lowers the risk of infection in rooms where infectious people are present.

According to the German Federal Environmental Agency, opening multiple windows, especially those across from each other to promote a draft, can greatly reduce the risk of getting infected with COVID-19. You have read that correctly -- opening a window can significantly reduce the chance of contracting COVID-19.

Diluting a glass of poison with more and more water

Supplying an indoor space with as much fresh air as possible, and especially completely exchanging the air in a room, can remove possible harmful airborne particles within a room.

Opening the window and allowing for proper ventilation can exchange used air with fresh air, therefore greatly reducing the aerosol concentration. The more fresh air is supplied, the more aerosoles are diluted within the indoor air.

Fresh air also ensures good air quality within the room. It can lower the indoor CO2 concentration to lower than 1000 ppm (0.1 vol-%) within a room, which indicates an adequate exchange of air under normal condition.

Studies have shown that fresh air with a low concentration of CO2 can greatly increase quality of sleep and next-day performance. And who doesn’t want that?

Open Window

What’s the best method?

You should aim to ventilate on a regular basis, especially if there is more than one person in the room. This should be done by opening the windows completely, what is called “shock ventilation”. If possible, open windows that are on opposite sides of the room in order to increase cross-ventilation, where fresh air can easily pass in and out of the space.

If you have a ventilation system in your bathroom or above your stove, you can turn these on as well to promote air exchange. However, only do this if the exhaust is led outside or if you have an open window or door to the room.

As a general rule of thumb, the German Federal Environmental Agency recommends shock ventilation for at least 10 to 15 minutes, and up to 20 to 30 minutes in the summer. However, during the depth of winter, even 5 minutes of proper ventilation has shown to be helpful.

But how often should you ventilate? The World Health Organization has recommended up to six changes of air per hour, and although that might be difficult to accomplish, the takeaway is clear: you should ventilate, especially if there are many people in the space, as often as possible.

Smart home products can help here too. Sometimes we all forget to open the window, even though it is necessary - we are too busy at work, bustling about at home, or leading our lives. A short reminder on your phone can help you keep your indoor air quality in excellent condition and promote a healthy lifestyle.

Just tilting the window, even for a short period of time, has not been shown to be particularly useful, as it doesn’t move air with enough force to exchange out potentially harmful particles. It could also increase your energy bill, because doing so can lower the temperature of your walls, making your heater work harder to produce the desired room temperature.

Old-fashioned methods still prove effective

Even within a hospital, preventing the spread of disease - including tuberculosis - can be greatly reduced by just opening a window.

Ironically, old-fashioned hospitals with tall ceilings and large windows are more effective in this job than modern “negative pressure” rooms, with modern ventilation machines pumping out infected air. Opening a window obviously requires little low-term maintenance and costs next to nothing.

Florence Nightingale, the British pioneer of modern nursing, actively advocated for fresh air and open windows to reduce infections in her Notes on Nursing from 1859. Little did she know that the reason why this was effective could be due to good microbes actively competing for resources with pathogens.

Last but not least, even the German Chancellor Angela Merkel champions ventilation and fresh air, noting it might be one of the cheapest ways of combating COVID-19. The German government has now included ventilation in their basic guidelines for preventing the spread of the virus.


Opening a window and letting in fresh air has been shown time and time again to greatly contribute to our overall health and well-being. Now we know it helps against the spread of COVID-19 and other infectious diseases.

On top of that, it is extremely cheap, requires minimal effort, and the results could protect you and your family.

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