How much bad air are we breathing in?
That is an issue artist Martin Nothhelfer hopes to raise in his cycling tour around Munich which started on Tuesday and ends tomorrow.
Dressed up as a cloud, Nothhelfer wants his mobile art installation to visually show just how much good or bad air is in the German city.
If the limits for air pollution are respected on a stretch of road, he presses a button on his bicycle that emits soap bubbles and cheerful music. If the quality of air is bad, another button releases smoke and plays a sombre tune.
According to Munich environmental organisation Green City, the statutory limit for air pollution is exceeded on about 120km of the city's main road network.