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Fresh air barometer
In it, the experts propose, among other things, the installation of CO2 meters or carbon dioxide traffic lights in classrooms. Since humans do not have a reliable physical sensor for air quality, “the CO2 content in the air is a good indicator of the amount of fresh air entering the room,” says Martin Kriegel, company director of indoor heating, ventilation and air conditioning. Hermann Rietschel Institute. Microbiologist Michael Wagner sees it similarly: “CO2 meters can provide valuable clues, as the concentration of the gas increases rapidly in poorly ventilated rooms.”
Green means that a solid fresh air supply is guaranteed. Yellow means you need to ventilate more, red indicates a hygienically questionable concentration, which generally occurs in conjunction with other air pollutants, particularly odorous substances (eg from sweat or cosmetics) and microorganisms. If a CO2 value of 1,000 ppm (parts per million, literally translated as “parts per million”) is exceeded indoors, ventilation must be provided.
However, a CO2 concentration of less than 1000 ppm does not automatically provide complete protection against infection. On the contrary, a higher concentration can increase the risk.
Learn to ventilate
In any case, the expert Kriegel is convinced that effective ventilation behavior can be learned with the help of CO2 traffic lights. In general, the need for ventilation is underestimated. In schools, but also in many offices, windows are often used for ventilation. “So, as a user of the room, you are responsible for the quality of the air.”
There will be no way around dedicated ventilation in the coming months. But how do you do it efficiently? “It’s important to ventilate high-traffic rooms frequently to reduce the concentration of viruses,” says Wagner. No specific general rule can be established, “since the frequency depends on the number of people and the volume of the room.” Continuous ventilation with the slanted window is comparatively unsuccessful.
The Ministry of the Environment advises schools to “ventilate intensively” every 20 minutes. Built-in fresh air systems are also an advantage in times of pandemic. Caution is applied to air conditioning systems with a high proportion of circulating air (in this case, little or no supply air enters the building from outside). They can contribute to the concentration of aerosols that contain viruses and represent a source of danger. If possible, air conditioning units should be switched 100 percent to outside air, and when buying new or older products, make sure that high-quality filters are installed.
