Why I built an e-paper room air monitor for my flat and how the first MVP works: monitor unit with e-paper display, sensor and LED panel -> storage and forwarding to a FastAPI backend with SQLite -> visualisation in an interactive dashboard. 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.