Safe CO2 levels often exceeded on crowded buses, trams and metros

Safe CO2 levels often exceeded on crowded buses, trams and metros
Credit: Belga

The permitted C02 concentration limit is often exceeded on crowded public transport, specifically on trams, buses and metros, a sampling has shown.

Belgium's recommended CO2 concentration of 900 ppm (parts per million) is often surpassed in crowded vehicles, a sampling conducted by VRT News found. However, this is not scientific research, but rather a sampling that aims to draw a wider picture of CO2 values on public transport.

At the end of November/beginning of December, 46 samples were taken with CO2 meters on the train, tram, metro or bus during rush hour in Brussels, Antwerp, Hasselt and Diest. Unlike at the start of the pandemic, there are currently no set limits for the maximum number of passengers on public transport.

Bigger cities, bigger problem

Half of the journeys on metros and trams in Brussels and Antwerp far exceeded the permitted CO2 concentrations. This was particularly the case in Brussels, where the threshold was exceeded ten times out of 14, including twice above 1,200 ppm.

"It doesn't surprise me that the value rises above 900 ppm," Marianne Stranger of Flemish Institute for Technological Research VITO told VRT News, as a lot of people sitting on public transport means that CO2 concentration will naturally rise.

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Stranger explained that these high levels are only a risk if there is an infected person present and that the risk also depends on how long someone remains in the vehicle.

By contrast, where samples were taken on trains the CO2 levels remained below 900 ppm.

Ventilation and taking responsibility

In response to the findings, Brussels public transport operators De Lijn and STIB both rejected the need to halve capacity on vehicles but reaffirmed the need for ventilation. They put the onus on passengers to check the occupancy of vehicles and adjust their routes accordingly.

Even at a low CO2 concentration of 500 ppm indoors, there is still a risk of contamination, according to the Flemish Care and Health Agency. When the value is above the 900 ppm threshold measures should be taken, such as opening the windows or leaving the room.

The use of CO₂ meters to monitor air quality became compulsory in gyms, bars and restaurants as well as schools in Belgium to lower the chances of virus particles accumulating and to draw attention to the importance of ventilation in indoor spaces.

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