Too dry, too warm, too stuffy – the air in schools, offices, and homes is not always healthy. Stuffy indoor air has actually been a hotly debated topic for years. Since this year, however, the question of the CO2 concentration in the air has become more alarming, because the proportion of CO2 indoors should also be a good indicator of the risk of corona infection or the virus concentration in the air.
What Factors Contribute to Good Air Quality Indoors
Three parameters in particular help to measure the air quality indoors: the humidity, the CO2 concentration, and the proportion of pollutants.
How does humidity affect air quality indoors?
According to the Federal Environment Agency, the ideal value for indoor humidity is between 40 and 60 percent. Dry air below 20 to 30 percent can lead to health problems. The airways can dry out because the concentration of airborne particles such as dust, pollutants, and bacteria is significantly increased as they are inhaled. In addition, the mucous membranes will dry out when the humidity is too low, which reduces the protective function of the mucous membranes in the mouth and nose.
Air that is too humid can, in turn, promote the growth of mold indoors in the medium and long term. In winter this would be at a value above 50 to 55 percent, and in summer at 60 percent. These values apply equally to offices as they do to apartments and schools. Humidity is also influenced by the people in the room, among other things. A person exhales around half a liter of water a day, and around one liter is released through evaporation through the skin, even if you don’t sweat. When showering and cooking, drying clothes and indoor plants, additional moisture escapes into the air.
The humidity is regulated via the fresh air supply. In rooms with windows, intermittent and cross ventilation is recommended. But air conditioning systems can also use sensors to measure the humidity and ensure the necessary air exchange.
How does the CO2 concentration affect air quality indoors?
The concentration of CO2 is another important indicator of indoor air quality. The outside air in Germany has about 400 ppm CO2. It is higher indoors, but should not exceed 1,000 ppm. The more people there are in a closed room, the higher the aerosol and CO2 concentration, since everyone continuously exhales CO2 and also aerosols.
Excessive levels of CO2 in the air cause drowsiness, and drowsiness can even lead to unconsciousness. People react to a CO2 content of between 1,000 and 2,000 ppm with malaise and reduced mental performance.
Certain studies have shown that the CO2 concentration in closed bedrooms can even rise to as much as 4,300 ppm during a night’s rest. Even if people are not consciously aware of the carbon dioxide in the air, it regulates the intensity of breathing. In order to get a good night’s sleep, doctors recommend ventilating bedrooms well. Here, too, ventilation systems with the appropriate CO2 sensors can ensure that the air is exchanged as required and that the CO2 concentration is kept lower.
How do volatile pollutants affect air quality indoors?
Numerous sources can adversely affect indoor air quality through pollutant emissions. Common indoor pollutants include volatile organic compounds. They are produced by building products, furniture, and other furnishings, which can usually continuously release chemical substances. When ventilating, the outside air can also contribute to the pollution of the indoor air.