4 questions about ventilation
Alvin Bartels, policy advisor on prevention of infectious diseases, RIVM:
Ventilation means constantly refreshing indoor air by bringing in air from outdoors. It makes it less likely that coronavirus particles will float in the air for extended periods.
Question: What was researched?
Bartels: We looked at different ventilation rates and calculated how much they reduce aerogenic transmission of the coronavirus. Aerogenic transmission means infection from inhaling virus particles[AB1] carried in tiny droplets, also known as aerosols, which can remain suspended in the air for a long time and float across longer distances. A person could potentially be infected from several metres away. Aerogenic transmission is not the same as direct infections from being close to someone who is contagious and
should stay 1.5 metres from others. In our research, we looked at the extent to which ventilation reduces the number of people getting sick. That means people
with COVID-19 who are showing symptoms. We ran these numbers for various scenarios, including a nightclub, a concert venue, a classroom and an office space.
Question: What are the results?
Bartels: Our calculations show that the main difference is between no ventilation at all, and ventilation according to the minimum requirements defined by the Building Decree. That has the biggest impact. This outcome was especially apparent in the nightclub and at the concert venues. We saw a significant drop in the projected number of symptomatic cases there. If you increase ventilation even more, it does reduce the risk of aerogenic transmission, but has a less significant impact on the number of symptomatic cases of COVID-19.
Question: Why is this research important?
Bartels: We know that ventilation is important in creating a comfortable and healthy indoor climate. Ventilation also helps to limit transmission of respiratory infections, such as COVID-19. However, it is unclear how much ventilation helps to prevent aerogenic transmission. The Ministry of Health, Welfare and Sport (VWS) therefore asked us to calculate that impact. Our results provide a bit more insight into this complex issue, and give the Ministry and the Cabinet additional resources for making policy choices.
Question: Can ventilation completely prevent coronavirus infections?
Bartels: No, that is not possible, not even with maximum ventilation. That is partly because ventilation primarily prevents aerogenic transmission. That is why ventilation is only one of the measures. It is still important to follow other measures, such as testing, staying home if you have symptoms, and washing hands.
TEXT: More information? www.rivm.nl/en/coronavirus-covid-19/ventilation