Ventilation matters: Prof Bert Blocken about the spreading of COVID

After our first-in-the-Netherlands media report on the risks that COVID seems to spread via aerosols, Radio 4 Brainport had another chance to speak to Prof. Bert Blocken. Time for an update.

Two years after our interview in March 2020, we know much more about how COVID spreads, but it has taken far too long before virologists and even the WHO took aerosols seriously. By now, the aerosol route is generally accepted as a serious risk. We now know that viruses cannot hop from one aerosol to another, but can travel far via directly exhaled aerosols when people cough, sneeze or just sing. There remains discussion about whether delayed infections can occur via air conditioning ducts that keep circulating the same air for prolonged periods. But it is clear that properly controlled air flow and air cleaning can avoid many infections that would occur in poorly ventilated rooms.

Scientific research addressed two stages: the airflow engineering research on the reduction of the risk of circulating infected aerosols and the medical virologists research question of to what extent small amounts of aerosols can still infect people.

Bert Blocken was heavily disappointed by how media, politicians but even scientists from other disciplinesmisinterpreted properly conducted engineering research. In particular, the engineering community has developed theories that are later used as common knowledge and common sense. One would not have to hypothesis-test the fundamental laws of physics. Nonetheless, there seems a lot of unjustified criticism to properly conducted research work. More seriously, he missed the acknowledgements from decision makers and even from scientists that certain things were not known at an early stage of the pandemic. It took the World Health Organization 16 monthsto take the aerosol risks seriously.

Reducing the risk of infection heavily depends on ventilation. A wide-spread misperception is that the best ventilation is natural ventilation. Well-designed buildings have mechanical ventilation that can effectively reduce infection risks. Indeed, controlled airflows are the most efficient, and are a proven technology in residential and other buildings worldwide. In addition, air cleaning is a proven technology as well, used in professional environments such as surgery rooms and clean rooms. In addition, UV disinfection can wipe out viruses in upper air areas in the room. In the interview with Radio 4 Brainport, Prof Blocken dives into details of how these systems can reduce viral load. In fact, at a series of schools in Belgium and the Netherlands, air cleaners are being installed in a new project.

But not all air cleaners are effective. Bert Blocken does not see it as a professor’s role to recommend specific products, but he sees an urgent need for the public to know what systems are effective and which are poorly performing. He recommends and urges governments and the EU to swiftly come with certification of aircleaning products.

These and more insightful stories, .. directly from the real Bert Blocken. Also, we hear about his personal journey of being a subject of debate, and even being impersonated on social media.

The interview was conducted via Teams. Archive Photo from 2019, when we chatted about cycling and wind tunnel research.