An exemple of particle concentration reduction in Parisian subway stations by electrostatic precipitation

The air quality in Parisian subway stations is a great concern to users and the public authorities. Particle concentration is one of the major problems; indeed concentrations observed in stations are generally superior to those collected in the street. The subway generates its own particles from wheels / rail contact, braking, the ground... One of the ways explored to lower this level of particles is a removal treatment: the principle is to treat the ambient air using a suitable system placed in stations. Following literature, the process chosen by Paris Transport Authority is the electrostatic precipitator. An electrostatic precipitator prototype from the Recycl'Air company is installed in May 2001 in a closed station on the 5th line (Italy Place -Bobigny). Results show that, by the end of approximately one year, the efficiency has fallen by 15% and it is therefore necessary to clean the precipitation cartridges. A consideration has also been made on the possibility to equip an entire subway station. According to the results obtained, about twenty filters placed in the top of a non mechanically ventilated station would permit to half an initial concentration in particles of 230 microg m(-3).