Air Quality in Italian Metro Stations: The Problem We Breathe Every Day

Metro stations are among the most critical urban environments from an air quality perspective. Every day, millions of commuters pass through spaces where fine particulate matter (PM2.5 and PM10) concentrations reach levels the WHO would consider unacceptable even outdoors.

The Data: What We Actually Breathe Underground

A study conducted between 2023 and 2024 across 8 Italian metro lines (Milan, Rome, Naples, Turin) recorded average PM2.5 concentrations between 80 and 210 µg/m³ during peak hours. The WHO daily limit is 15 µg/m³. We are between 5 and 14 times above the safety threshold.

There are three main causes: braking of cast-iron wheels on rails (generating ultrafine metal dust), insufficient ventilation in historic tunnels, and the progressive accumulation of particulate matter in tunnel chambers without active filtration systems.

Why Public Infrastructure Must Act Now

The European air quality directive (2024/2881/EU) extends monitoring obligations to semi-enclosed spaces in public use. Metro stations fall within this category. Operators who do not upgrade their systems by 2027 risk fines and, more importantly, civil liability in the event of health damage to workers.

On the workers' side, station staff spend an average of 6 to 8 hours a day in these environments. Prolonged exposure to metal particulate matter is associated with occupational lung conditions documented by INAIL since 2019.

Available Solutions: Certified Purification and IoT Monitoring

Not all purification systems are effective against the metal particulate typical of metro stations. Standard HEPA filters capture organic PM2.5 but struggle with ultrafine metal dust (< 0.1 µm) generated by rail iron.

E-Bufaga devices use a combination of hybrid filtration (HEPA H14 + impregnated activated carbons) and controlled ionisation, which also acts on the finest fractions of metal particulate. Each unit covers approximately 150 m² and transmits certified data in real time via IoT to the operator's control panel.

Real Case: The Collaboration with ATAC Rome

The collaboration with ATAC enabled the installation of E-Bufaga devices at 3 stations on Rome's Line B. After 90 days of continuous monitoring, PM2.5 concentrations in the monitored areas fell by 67% compared to the pre-installation baseline. The data is certified by an Accredia-accredited third-party laboratory.

How to Calculate the Impact for Your Infrastructure

Every station has different characteristics: passenger area floor space, number of platforms, traffic intensity. The Bufaga calculator estimates in seconds the number of devices required, the PM removed annually, and — for stations with advertising displays — the ADV revenue the network generates.

If you manage a public transport infrastructure, you can also request the PA Dossier: a technical document with sector benchmarks, an updated regulatory framework and a customised simulation. It is free and delivered within 48 hours of request.