Service on Naples Metro Line 2 has still not returned to Pozzuoli after the closure of the Pozzuoli railway tunnel because of anomalously high carbon dioxide concentrations. A new phase of monitoring and testing, carried out directly aboard trains, is intended to assess whether the line can resume service safely.
The test programme is expected to measure CO2 concentrations aboard trains over several days, across different time bands and using different train types and ventilation configurations. The plan also includes simulations of prolonged train stops inside the tunnel.
According to the Campania Region, continuous monitoring and the installation of ventilation turbines had significantly lowered CO2 concentrations in the tunnel. Technical, scientific and health-related assessments were still continuing before any reopening.
The safety evaluations involve RFI, Campania Civil Protection, the fire brigade and other public institutions. The authorities have stated that reopening will occur only after safety conditions for passengers and onboard staff have been demonstrated.
What the tests will check
The central question is what passengers and crew would actually breathe inside the tunnel. Measurements taken aboard moving trains, and during simulated prolonged stops, are meant to test real operating conditions rather than tunnel air alone.
Different days, time bands, train types and ventilation systems are included so results do not depend on a single set of conditions.
Why the Pozzuoli section remains closed
The Pozzuoli section was closed after unusually high CO2 levels were found in the tunnel. Ventilation and monitoring have improved the picture, but officials have not treated that improvement as sufficient on its own for reopening.
Further technical and health assessments are required first.
What is still unknown
No reopening date has been established in the sources available. The published reports also do not give the measured CO2 results from the new train tests.
It is also not yet clear from the available reporting whether the full section or only part of it would reopen first.
For travellers, the practical point is unchanged for now: Line 2 service has not yet been restored to Pozzuoli, and return depends on the outcome of these safety tests.
