Designed for continuous outdoor deployment across real-world environments.
RECAP
Project Summary
Persium has joined a high-level consortium with Transport for London (TfL), RATP (Paris), and Imperial College London, supported by EIT Urban Mobility, to deploy specialised air quality sensors across subsurface metro environments.
Unlike surface-level pollution, underground air quality is dominated by metallic particulate matter generated from brake wear, wheel friction, and rail abrasion. Persium Pods are engineered with specialised casings and self-cleaning mechanisms to maintain data integrity under the extreme particulate loads found in deep-tube tunnels.
The Challenge
The London Underground, the world's oldest subway, presents an environmental monitoring challenge that standard surface sensors cannot meet. Particulate matter in deep-tube environments is primarily metallic, generated continuously by the friction of brakes, wheels, and rails.
High particulate loads rapidly compromise standard sensor performance, and the enclosed, high-traffic nature of the network means poor air quality directly affects millions of daily commuters and the staff who work underground every day.
Persium
Deployment
Persium Pods deployed across the London Underground and Paris Metro are engineered specifically for subsurface performance, drawing on technology originally refined for steel plant environments, with specialised casings and self-cleaning mechanisms designed to maintain accuracy under sustained heavy metallic dust exposure.
Parameters monitored include:
• Particulate Matter — PM1, PM2.5, and PM10
• CO₂ and Volatile Organic Compounds (VOCs)
• Temperature, pressure, humidity, and noise
Monitoring through Dashboard & MapView
All data streams into Persium MapView, providing TfL with a live, networked view of air quality conditions across stations and tunnel sections.
This enables real-time identification of pollution peaks and troughs, evidence-based targeting of track cleaning and air filtration interventions, trend analysis to assess the impact of maintenance changes, and continuous monitoring of passenger and worker exposure conditions.
What This Enables
Continuous, high-resolution monitoring gives TfL and RATP the intelligence to manage commuter air quality proactively, optimising track cleaning, refining filtration strategies, and demonstrating environmental performance across some of the world's most heavily used public transport infrastructure.
With Imperial College London as a research partner, the deployment also contributes to the academic evidence base on subsurface air quality and commuter exposure.
Managing the air where millions of people move every day.
Talk to our team about deploying Persium across your transport network or infrastructure environment.