Correct Ventilation - How CO2 Traffic Lights Can Help

Correct ventilation improves performance and reduces the risk of viral or bacterial infection in indoor environments. But what does correct ventilation mean? How often and to what extent should windows be opened and how can you be sure that ventilation is actually sufficient and correct? CO2 traffic lights measure the CO2 content of the indoor air and indicate when it is time to ventilate.

Aerosols: Why Correct Ventilation in Offices and Classrooms Is Important Right Now

Aerosols are microscopically small particles invisible to the eye which are exhaled with the air we breathe. Depending on their size, they can remain in the air for several hours, or even days, and can contain viruses. Since the volume of air indoors is limited, aerosols quickly spread throughout the room. This also increases the risk of contracting a pathogen if several people are in the same room. Correct ventilation is an important and effective measure to reduce the risk of infection. 

Correct Ventilation – How to Do It:

  • How do I ventilate correctly? 
    The quickest and most effective way to exchange air is to open opposite windows at the same time. However, cross-ventilation is not always feasible in practice. Even airing the room by opening several windows wide is effective, provided the windows remain open for a few minutes. Tilting windows is not useful – even over a longer period of time. 
  • How often should I air the room?
    Basically, the more people there are in a room, the more often it should be ventilated. The CO2 concentration rises rapidly in rooms with a high density of people. The higher the CO2 content, the lower the proportion of fresh air in the room. This also increases the probability of infection due to aerosols. For this reason, meeting rooms/offices and school classrooms should be ventilated at regular intervals and, above all, correctly. When and how long ventilation should be provided depends on the respective room situation and occupancy. A CO2 traffic light helps to individually assess the need for ventilation.

A CO2 Traffic Light Indicates When You Really Need to Air the Room

CO2 traffic lights indicate whether ventilation was correct or incorrect and, above all, when it is time for the next air exchange. According to the Indoor Air Hygiene Commission (IRK) of the German Environment Agency, ventilation behaviour can be monitored and correctly controlled by measuring the CO2 content of the air¹.   

At a CO2 value of over 1,000 ppm, the indoor air in offices, for example, is perceived as unpleasant. This not only causes headaches and lack of concentration, but also a greater exposure to viruses. 
If the CO2 traffic light shows a value of less than 1,000 ppm (0.1% by vol.), this is a sign that the air has been changed in a "hygienically adequate way"² . 


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