Christmas is a good time to rethink bad old habits, like too much time spent driving cars. That's why the lights of the tree integrate into the festive townscape, while also warning people about the alarming air quality.

Almost 10,000 LEDs in 40 acrylic glass tubes illuminate the 20 meter high tree in front of Wiesbaden's main train station. In combination with real-time readings from the Hessian Agency for Nature Conservation, Environment and Geology (HLNUG), the lights display information about the current amount of nitrogen dioxide in the air. If the LEDs light up red, the quantity of NO2 is above the EU limit (40 µg/m3). If they light up green, the city air is "clean" – a rarity for the city.

While the lights are on display, the measured air quality values are displayed and recorded on www.noxmas.de. Each day is displayed via a graphic representation showing the complete day's measurement data, similar to a clock. As a result, even after the live installation ends, the NOxmas project will not diminish in importance and will remain relevant and accessible to the public.

The Hessian Agency for Nature Conservation, Environment and Geology (HLNUG) measures the air quality in real-time and saves it in abstract lists. Thereby the large amount of nitrogen dioxide in the air is a health risk which the population has actually to be made aware of. With the real-time illumination on the huge tree and the visualisation on www.noxmas.de the current state of the air quality could be seen by everyone anytime.

The NOxmas project will remain relevant and accessible to the public. After a lot of positive feedback and requests from numerous cities, the website will soon show the current amount of nitrogen dioxide in the air of 462 municipalities across Germany.