ERA presents manual for Covid-safe train ventilation
Keep individual ventilation closed, but turn on ventilation systems and use natural ventilation as much as possible to get harmful aerosols out of the train. These are some of the advice that the European Union Agency for Railways (ERA) collected in a Covid-19 information bulletin with technical advice on ventilation in railway vehicles.
The exact role of aerosols in transmitting SARS-CoV-2 infection and the spread of the Covid-19 pandemic has not yet been fully established. What is certain is that aerosols weaken as the distance to the source increases, but can concentrate in tight, poorly ventilated spaces. Droplet infection is Corona’s main route of transmission to date. However, the World Health Organization (WHO) recently recognized the importance of potential airborne transmission of aerosols containing SARSCoV-2.
Therefore, according to experts, it is better to leave ventilation systems switched on to evacuate potentially harmful aerosols. Turning off ventilation systems can cause them to build up in the passenger compartment. ERA recommends turning on the ventilation well before the passengers arrive, keeping the ventilation on between trips and running as much as possible at the end of the shift.
In addition, the advice from ERA is to ventilate naturally as much as possible. This means: open all doors during stops and open windows if possible. The bulletin also discusses in detail the recirculation of air in the air conditioning, ventilation and heating systems of trains. These systems use both outside air and air extracted from the vehicle. Up to 90 percent of the ventilated air volume can consist of recirculated air. This ratio can be determined automatically by the system or be fixed.
Do not recirculate
Recirculation of air is often chosen to save energy and increase comfort. After all, the air is already heated or cooled, the outside air is not. In order to prevent the virus from spreading, the ratio must now be set to the largest possible percentage of outside air. Depending on the system, this can be set on control panels, but it may also require a software update, the removal of CO2 sensors or the closing of suction openings.
These adjustments can cause travelers to experience less comfort because the systems no longer manage to reach the expected temperature. Especially under extreme weather conditions. Furthermore, slight overpressure in the train can cause delays in closing doors. Overpressure when entering tunnels and passing trains can put pressure on travelers’ ears. ERA advises operators to test beforehand and check how modified systems respond. “Also ask the manufacturer for advice on the best method for adjusting settings.”
Not an effective filter
The bulletin simply states that air ducts and filters should be kept as clean as possible. The fact that filters can get the virus out of the air or keep it out of the train is still an illusion. The filters used in trains are not fine-meshed enough to trap the virus, according to ERA. So-called HEPA filters can do this. However, their application requires such a major adjustment of the current systems in trains that they are not seen as a workable option. Another option could be the use of ultraviolet radiation. This can kill harmful bacteria. An workable application of this has not been found yet for trains.