During sleep, we release a lot of moisture: on the one hand through our breathing, and on the other through night sweating. Per person, considerable amounts of up to 700 ml of water quickly accumulate in the air, the mattress or the bed linen. But not only the absolute humidity (φ) increases, but also other air values. Of interest here are carbon dioxide (CO₂) or volatile organic compounds (VOC).
Better to open the window at night? The air-Q self-experiment
We asked ourselves: should you sleep with the window open at night or is it enough to ventilate well before sleeping? To answer this question, we conducted two different tests with our air meter: On the first day, we only ventilated before sleeping, while on the second day, the windows remained open the entire night. To make the data comparable, the starting situation for our test always remained the same: an approximately 9m² bedroom in the attic, including sloping ceilings and two windows, as well as two adult test subjects.
Practical test 1: Is airing before sleeping enough?
On the first day of the trial, the room was ventilated for a longer period before going to bed, so that the initial CO₂ levels were relatively low at around 11:30 p.m. at below 500 ppm (parts per million). After the windows were closed, however, the carbon dioxide content in the room air quickly rose sharply, reaching the first peak of just under 2,000 ppm after just one hour. After a brief ventilation period of about 15 minutes, the air-Q air meter indicated that the levels had dropped to about 1,2000 ppm. This is still an elevated CO₂ level.
After closing the windows again, the carbon dioxide content rose sharply once more and reached its second peak of just under 2,500 ppm at around three in the morning. The indoor air was noticeably bad and relaxed sleep was no longer possible. Therefore, the windows were opened from three o'clock and left open for the rest of the night. Due to the two high peaks, the average carbon dioxide load was nevertheless 1082 ppm and thus exceeded the limit value of 1,000 ppm recommended by the Federal Environment Agency.
Field test 2: Is sleeping with an open window healthier?
On the second day of the test, the air was not ventilated via open windows before going to bed, but only the door was left open. Therefore, in contrast to the previous day, the air-Q showed higher initial values of 680 ppm. Shortly before going to bed at about 24 o'clock, both skylights were opened. Since there were now two adults in the room, the CO₂ level initially rose to about 750 ppm. However, this peak is significantly lower than the maximum values of the first experiment with the window closed. After the peak, the air-Q air meter detected a significant drop in carbon dioxide levels in the room air. By shortly before half past two, the values had dropped to around 600 ppm, well below the initial values. Between three and five in the morning, the air-measuring device showed fluctuations in the CO₂ deflections. Further smaller peaks were recorded here, but their values stabilized again and again. From six o'clock on, the CO₂ content normalized and leveled off between 620 and 630 ppm. The average carbon dioxide content was 653 ppm, well below the limit recommended by the German Federal Environment Agency.
Conclusion
Our practical test clearly shows that sleeping with an open window is healthier. This is because the charts of our air-Q app show a constant exceeding of the recommended limit values during the first test. If, on the other hand, the window remains open while sleeping, the CO₂ values also fluctuate, but always remain within the inconspicuous normal range. So anyone who has the opportunity to sleep with the window open (without disturbing street noise, for example) should take advantage of this. In addition to a sufficient supply of fresh air, you can also improve the air quality in your bedroom with suitable green plants. Our practical tests with dragon tree and bow hemp show which species are particularly suitable here.
(Contributed image: KatarzynaBialasiewicz from Getty Images Pro/ Canva)
