Caring about air quality in our spaces
To improve air quality, we constantly monitor and analyse the air that circulates in our underground rail networks. We focus our efforts on improving air renewal in our spaces (with a programme to create, strengthen and replace ventilation systems) and the optimisation of electric braking for our rolling stock (to reduce particles emitted by mechanical braking).

Our monitoring is geared primarily towards ensuring that we respect sanitation and cleanliness standards in our spaces, those used by passengers as well as those used by our employees.

Using the SQUALES (Surveillance of Air Quality in Underground Environments) network, our laboratory conducts continuous measurements in premises that are representative of RATP’s underground spaces: two metro stations, at Franklin D. Roosevelt (line M1) and Châtelet (line M4), and one RER station, at Auber (RER A). We measure standard climatic parameters (temperature, relative humidity) as well as air renewal (carbon dioxide) and air quality (nitrogen oxide, particulate matter).

Key number

items of raw data concerning sanitation and cleanliness are collected each year

One-off measurement campaigns are also conducted on platforms, connecting hallways and transfer hubs, which allow us to monitor other parameters such as ultrafine particles (UFP), aldehydes and polycyclic aromatic hydrocarbons (PAH).

Our verdict? Thermohygrometric conditions are satisfactory, but there is room for improvement

Our observations reveal a warm and dry underground environment, with good air renewal (4 to 40 air renewal cycles per hour) and a limited presence of nitrogen oxide from outdoor pollution.

Yet we did observe high levels of metallic particles (PM10, particulate matter with a diameter of less than 10 µm), emitted primarily by our rolling stock’s historic mechanical braking systems.

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What about other rail networks?

We exchange information on air quality issues with foreign rail networks (Stockholm, London, etc.) via the International Association of Public Transport (UITP).

A summary of research work conducted on other French rail networks (Lyon, Toulouse, Rennes and Lille) shows that air quality is similar to that measured in Paris. In Toulouse and Lyon, the hourly maximum value of PM10 ranges between 200 and 500 µg/m³. In London, punctual measurements point to values ranging between 500 and 1,120 µg/m³.