The pupils at Hampstead Hill Pre-Preparatory and Nursery School will be able to breathe cleaner and fresher air during their break from now on. The independent school has installed two innovative air filters on the playground that use real, living moss to clean fine dust particles from the air and enrich it with oxygen. The CityTree is really cool because it cleans the air so we can breathe and play in the clean air These innovative and award-winning biotech filters from German company Green City Solutions combine natural moss with innovative technology. One of these filters, dubbed CityTree, can purify up to 3,500 cubic metres of air per hour — roughly equivalent to the hourly breathing volume of 7,000 people. In addition, a CityTree removes up to 82% of especially harmful fine dust from the air. The students are enthusiastic about CityTree – Sarah Brown (age 7), explains: “The CityTree is really cool because it cleans the air so we can breathe and play in the clean air. It has a door and inside there are lots of pipes. They help the moss to water itself! Our city tree is so special because our plants and animals are very important to us and pollution could kill all these species. We don’t want that because they are so important to our planet.” The positive effects go beyond air purification. Due to its large surface area, the moss in a CityTree can absorb about ten times more CO2 than an average 10-year-old tree. Plus, the filtered air is noticeably cooler — a refreshing effect that students and teachers will surely appreciate, especially in the warm summer months. “Our mission is to find a solution for particularly polluted inner-city spaces, so that as many people as possible can breathe clean air,” explains Peter Sänger, co-founder and CEO of Green City Solutions. “And we are pleased that in this case, children in particular will benefit from the improved air quality”.