“However, the Vindriktning shows you a green light until 35 μg/m³ which is SEVEN TIMES the WHO air quality guideline.”
The sensor costs Ikea a few dollars and uses an LED instead of a laser. Ikea sells it as a PM2.5 monitor, but the spec counts particles up to 10 microns. Green means seven times the WHO limit. Yellow, which the manual calls OK, is already unhealthy by US standards. A ten euro gadget that tells you bad air is fine is worse than no gadget.