Byens Luft is a free Android application designed for individuals particularly vulnerable to air pollution, such as children with chronic illnesses, pregnant women, and those suffering from respiratory or heart conditions. This app provides air quality forecasts for 103 locations across Copenhagen, extending up to four days ahead. Users can subscribe to alerts that notify them when pollution levels are predicted to be extremely high in various areas of the city. The forecasts are based on a quality index developed by the DCE – National Center for Energy and Environment at Aarhus University.

In addition to forecasts, Byens Luft offers detailed information regarding expected levels of fine particles (PM2.5), coarse particles (PM10), nitrogen dioxide (NO2), and ozone (O3). Users can also access historical measurement data from the past day from six monitoring stations throughout Copenhagen. This comprehensive approach helps residents make informed decisions about their outdoor activities based on real-time air quality data.