Technical Paper TP06: Options for Treating Road Tunnel Emissions

The use of tunnel air filtration systems is not common worldwide and such systems present the challenge of capturing and treating high volumes of tunnel air with very low pollutant concentration levels (compared to industrial applications). This results in high infrastructure, operation and maintenance costs. To date, particulate filtration in tunnels is based solely on the use of electrostatic precipitators. The use of air treatment systems for nitrogen dioxide (NO2) is a rarity and has currently only been implemented in full scale
in the Calle 30 Madrid tunnel projects, as an alternative to stack dispersion.
Any decision making process concerning tunnel air management (portal air management as well as air treatment systems) needs to prioritise health based air quality standards when considering engineering and economic practicabilities, and can only be made at the project level. While an air treatment system for particulates or NO2 may be technically feasible, energy usage is high and it will not lower concentrations of other pollutants. Alternatives such as portal air extraction and stack dispersion may achieve the same outcomes at a reduced cost