Ventilation and masks improve health security on public transport

According to a report commissioned from Technical Research Centre of Finland VTT, the risk of transmission on public transport seems to be very low when complying with the safety instructions issued for public transport. VTT studied the amount of airborne particles that travel more than two meters and their impact on the health security on public transport.

If passengers wear masks on public transport, the risk of transmission is minimal when maintaining a distance of over two meters. Wearing a mask further reduces the amount of droplets and aerosols. The typical way of travelling in silence on public transport is also beneficial: a noisy passenger produces droplets up to four times as much as the usual, quiet passenger.

“In addition to wearing a mask, you should keep your distance from others as much as possible, as it reduces the risk of droplet transmission and short-range aerosol transmission. And good hand hygiene reduces the risk of contact transmission,” says researcher Ilpo Kulmala from VTT.

Ventilation of the vehicle also impacts the amount of particles in the air. On public transport, a particularly efficient and easy way to boost ventilation is to open the doors at a stop. It can reduce air aerosol concentration by up to one third.

“It is an effective way to increase ventilation, although it may cause a draught in winter weather,” Kulmala says.

On urban public transport, ventilation is naturally fairly good. The journeys taken in one vehicle are typically relatively short – the average travel time on HSL’s transport services is 9 minutes on trams, 11 on the metro, 12 on trains and 14 on buses. The vehicles also stop often, which means that the doors are opened frequently even in normal situations.

According to VTT’s report, the ventilation HSL public transport is at a good level when compared internationally. The assessment looked at ventilation on buses, the metro, commuter trains and trams.

Most people are mindful of wearing masks on HSL public transport at the moment. Around 80% of passengers wear masks.

“We would like to thank our passengers for following the safety instructions. We will be working to guarantee safe and reliable public transport in the future, too,” says Tero Anttila, Director of HSL's Public Transport Department.