AeroSolfd is an EU co-funded innovation action developing retrofit filtration solutions as a fast track to cleaner urban air. A particular focus is on developing, installing, and testing filtration devices for improving air quality at metro stations. Per day more than 100 million people are commuting by metro. Metro networks are the backbone of the economy in bigger cities and contribute to reducing inequality by affordable transport options. However, the semi-closed environment of a metro station, in particular underground, is usually not primarily designed considering air quality and studies confirm it by demonstrating that concentrations of respirable particles in metros and their stations are high, and usually higher than those in the ambient environment (e.g., Martins et al., 2015). Providing good air quality, both inside trains and at the stations, is a key and challenging objective of metro operators. Primary local sources of particle emissions are brakes and rails. But there are many other factors influencing the air quality (e.g., the design of station, ventilation systems, trains’ frequency, etc.). Studies show that each station is different. Nevertheless, a flexible, scalable filtration solution to be installed as ‘retrofit’ at the platform would be a promising option for improving air at existing and new stations.

The 3-year innovation action AeroSolfd started in May 2022. First results can now be reported: The design of the air purifiers has been updated for use at metro stations. Emissions of metro brakes have been analyzed to find a good tracer. Air purifiers have been installed at a metro station in Lisbon. We are going to report on the progress, present and discuss the setup at the metro station in Lisbon as well as results on air quality measurements.