TL;DR – In the cold season we tend to keep the windows closed. The air gets "stale": humidity often rises above 60 %, which can harm our wellbeing and promote mould. At the same time the CO₂ level in the air increases, which impacts our ability to concentrate. So I built a room air monitor that stays unobtrusive as long as everything is in the green zone, but becomes deliberately noticeable once thresholds are exceeded. For my personal love of statistics I also visualise the measurements in a clear dashboard.
Note: This English version was created with the help of automated translation and I am not a native English speaker. If you notice any unclear or incorrect wording, feel free to point it out in the comments or reach out via e-mail so I can improve the text.
Why this project?
When windows stay closed for longer periods, the air indoors quickly becomes “stale”. Both humidity and the CO₂ level rise. CO₂ is measured in parts per million (ppm) – essentially “CO₂ molecules per one million air molecules”. This makes it easy to compare how much more CO₂ is present indoors compared to fresh outdoor air. At elevated levels, the following issues can occur:
CO₂ level Meaning / possible effects around 400-450 ppm (typical outdoor air) Baseline for fresh air. up to ~1 000 ppm Often used as an upper limit for good ventilation. Values above ~1 000 ppm indicate insufficient ventilation. about 1 000-1 500 ppm Concentration rises – reduced performance, concentration problems and tiredness become more likely. > 1 500 ppm or more Very poorly ventilated room. Health and comfort issues become more frequent. Extreme values (e.g. > 5 000 ppm) Severe symptoms possible, e.g. shortness of breath or loss of consciousness. Very rare in normal indoor environments.
Source: ASHRAE (2022). ASHRAE Position Document on Indoor Carbon Dioxide – PDF
Humidity that is too high or too low is also unhealthy. If it is too low, this leads to dry mucous membranes, irritated skin and a higher susceptibility to infections. If it is too high, it promotes mould growth, dust mites and other bio-organisms that can contribute to respiratory illnesses, allergies and asthma.
Relative humidity (RH) Meaning / possible effects < 30 % Very dry: irritated mucous membranes, dry skin, eyes, possibly nosebleeds, increased susceptibility to respiratory infections. ~30–40 % Often quoted as the lower bound of the “healthy” range. ~40–60 % Frequently recommended ideal range for indoor spaces in terms of health and comfort. > 60 % (up to 75 %) Risk: increased mould and mite growth, damp rooms, uncomfortable indoor climate. Very high (> 75 %) High humidity + poor ventilation = substantial health and building risks (mould, respiratory diseases).
Source: Wang, W., Zhang, X., & Li, W. (2023). Effects of indoor humidity on human health and comfort: A systematic review. Building and Environment – article
All of this shows how important regular airing is. The e-paper room air monitor helps my flatmates and me to keep these values in check and maintain a healthy indoor climate.
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