It is not only in schools and workplaces that it is necessary to keep an eye on air quality and to take countermeasures when limit values are reached. In our private lives, in our homes or while meeting friends indoors, we should also monitor air components. And not only during a pandemic. Now relaxations are on the horizon and we can slowly return to our old lives. But even in normal everyday life, we need to make sure we ventilate regularly and check the air quality. Our experiment shows why this is necessary even without an aerosol load.
Carbon dioxide: The measured value for "bad indoor air
Besides viruses, other air components also influence the quality of indoor air and thus our health and performance. Special attention should be paid to the carbon dioxide content (CO₂), which is spread by the exhaled air, among other things. When we breathe in, we take in oxygen from the air. When we exhale, on the other hand, we release carbon dioxide into the air. While the inhaled air contains 21 vol. % oxygen and 0.035 vol. % carbon dioxide, the values of the exhaled air change to a 16 vol. % share of oxygen and a significantly increased share of carbon dioxide of already 4 vol. %. Carbon dioxide is an odourless and tasteless gas. Although it is neither visually nor olfactorily detectable, its negative properties are noticeable to humans and animals. A high CO₂ concentration is reflected in malaise, poor concentration and a drop in performance. Although it is only toxic at a concentration of 2.5 % by volume, performance, concentration and well-being are already reduced at a concentration of 0.1 % by volume. This corresponds to a valence of 1,000 ppm - i.e. a mass fraction of one milligram per kilogram.
Especially in closed rooms where many people are present, the CO₂ rises sharply after just a few minutes and reaches values of 5,000 to 6,000 ppm.
The air-Q test: How does the indoor air change when several people are in a room?
We wanted to know how much the CO₂ levels change in a room when several people come together. For this purpose, we set up the air-Q air measuring device at a private party of 10 people in a kitchen in Leipzig on 8 January 2022 and documented the change in the measured values. Our test took place in a room of about 12 sqm with an air volume of about 33.6 m3. Before the party, the room was well ventilated and showed a CO₂ value of about 600 ppm. The air measuring device indicates when limit values have been reached by means of illuminated LEDs. If the CO₂ level reached the limit values, the air-Q indicates this by means of a red flash of the LEDs. In these cases, the windows were opened and ventilated for about 5 minutes.
Around 8:30 pm, all the guests had arrived. The CO₂ level quickly rose to over 2,200 ppm. After a short ventilation interval, during which the load could be reduced to 1,600 ppm, the value rose again and reached the maximum value of about 2,300 ppm. Further ventilation intervals at around 10 pm, one o'clock and two o'clock minimised the CO₂ load. However, the initial value was clearly exceeded each time. Thus, by ventilating at half past one, only a CO₂ value of 1,200 ppm could be reached.
During the party, some people did not stay in the kitchen, our experimental environment, the whole time. Thus, the balcony was also used for smoking. This is particularly evident in the increase around two o'clock. Cigarette smoke influences the CO₂ level, even if it is not smoked in the room, but the smoke "only" enters the room through breathing and attaching to clothing.
The average CO₂ level during the period studied was 1,645 ppm - well above the recommended limit of 1,000 ppm. Again and again, the carbon dioxide in the room increased within a time interval of 30 minutes and reached maximum values around 2,300 ppm.
Our test results show that even short ventilation intervals of about 5 min. noticeably reduce the CO2 concentration. In the course of the evening, however, the CO2 level rose faster and faster and could not be reduced to the initial value even despite ventilation breaks. For a constant reduction of the CO2 value, either the ventilation frequencies or the ventilation duration would have to be significantly increased.
Alcohol & crowding affect the VOC level in a room
Not only does oxygen "disappear" from a room when many people come together, but also dangerous substances suddenly increase in the air composition. For example, volatile organic compounds (VOC), whose increased concentration enormously reduces well-being. An increased VOC concentration in the room air makes people tired and is manifested by the combination with odorous substances in the typical perception of "stale air".
However, high VOC levels are not only unpleasant for the nose, but also have consequences for health. VOC pollution is manifested by the following symptoms: altered smell and taste perception, irritation of the eyes and mucous membranes, lack of concentration, exhaustion, dry skin and a tendency to eczema and headaches. The vapours of alcohol influence the VOC value in indoor spaces. Our test also shows this. In the course of our party, there were more and more open bottles on the kitchen table.
Our test shows a constant increase in the VOC load, interrupted by the short ventilation intervals. But here, too, it becomes clear that the low initial value of about 100 ppb could no longer be reached shortly after eight o'clock. Thus, after ventilation at shortly before two o'clock, the 2,200 VOC value even exceeded the limit of 2,000 ppb. Maximum values of 5,000 to almost 8,000 ppb were measured at five time intervals between ventilation breaks.
How high is the noise level at a small party?
In addition to the CO2 and VOC values, the air-Q also analysed the noise (Lp). Here, the evaluation shows that the noise exposure was 75.29 dB on average. An increased noise level also impairs well-being and performance. When whispering, the noise level is around 40 decibels. If you live on a main road or work in a noisy open-plan office, you are quickly exposed to a sound level of 80 dB. As a rule, noises of up to 65 decibels are considered "normally" loud. On the other hand, permanent exposure to sound at a level of 80 to 85 dB can cause permanent damage to hearing.
As a remnant of our ancestors, noise puts our entire organism on alert: we are ready to flee at any time. This tension means stress for the body. At noise levels of 60 decibels or higher, the amount of the stress hormones cortisol and adrenaline in the body increases. The heart rate and blood pressure also increase. Noise therefore changes the hormone balance. But it also affects metabolism and brain wave activity. Those who are permanently exposed to noise risk permanent hearing damage and can promote depression. We have summarised more information about noise and its physical and psychological effects in a separate article.
With the air-Q you can keep an eye on the air quality in real time: at a party, in everyday life or in the office. The intelligent air measuring device can detect sources of air pollutants and you can take appropriate countermeasures thanks to the warnings.
(Contributed image: Canva edit/ LightFieldStudios from Getty Images)
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