Reducing dust on London Underground

Project objectives

Our monitoring shows that airborne particulate matter (PM) levels on the Tube are below occupational limits set by the Health and Safety Executive (HSE), but we're not complacent.

We're looking for information on new ways to improve air quality in London Underground stations, passenger carriages and driver cabs.

The goals of this exercise is to:

  • Understand what additional solutions are available to supplement the work already taking place
  • Understand what technologies exist in other industries that could be applied to this problem area
  • Gauge suppliers' interest, capabilities and capacity to engage in a trial

Why take part

We are working towards a greener, safer, more inclusive future for London. To get there, we know we need to tap into the skills and expertise of market innovators. We also value learning from other countries and analogous industries.

Your response to the market sounding questionnaire will help us to build a greater understanding of what types of solutions are available to us and shape of possible funded trials later on.

The problem of dust

The accumulation of dust is a common feature of all underground networks across the world, and London's Tube network is no exception. Trains moving over rails, engineering works and customer use all contribute to dust levels. We are working to reduce dust on the Tube to ensure the air quality there stays safe for our staff and customers.

Besides the HSE legal limits, we also measure London Undergroun against lower limits recommended by the Institute of Occupational Medicine (IOM) and in most cases levels are also below those lower limits.

Dust on the Tube is made up of a mix of:

  • Metal particles - most of which are iron oxide
  • Organic matter like skin and hair
  • Mineral dust

These materials originate from several different sources. It mostly comes from the wheels and rails, through general use and maintenance. It can also come from braking.

We use different types of braking, but friction braking is what most commonly creates metallic swarf (small pieces of metal). Higher train frequencies also contribute to PM concentrations because increased acceleration and faster braking is required. Modern trains use friction brakes less.

Solutions we're looking for


We're interested in filters which catch inhalable (<100µm) and respirable dust (<4µm) fractions.

  • Static dust filters. We would need them to have a good air flow rate (m3/h), not be too big, or too noisy.
  • Vent filters. We would need them to fit out rolling stock grilles, be affordable, and not increase the frequency of how often they need changing
  • Electrostatic filters. We would need them to not be cumbersome to clean or maintain.

Learn more about our strategy and ambitious goals for cleaner air on the Improving air quality on the Tube page.


We would need the cleaning equipment to be easy to get down onto the tracks and to be relatively unobtrusive, so as not to cause damage, for example to the signalling system. Equipment could only be used during engineering hours (01:00-04:30) and couldn't compromise service the next morning.

Rolling Stock

The parts listed below would need to suit our rolling stock specifications, and not compromise on safety or performance.

  • Brake blocks
  • Stick lube
  • Current collector shoes and wheels materials


  • Permanent monitoring devices. We would need sensors to be easily and affordably retrofitted into our trains, stations, equipment and tunnels. We would also need them to be easy to connect, calibrate and maintain.
  • Data management platform. We would need the data platform and associated software to be open source, easy to access and conduct analysis, and possible to integrate into our existing systems.

Open Call

We are also open to ideas that we have perhaps not yet considered
For example:

  • Friction brake conditioning
  • Ventilation/fans
  • Localised dust capture

Supporting information

Contact us

If you need any other information, email us at