After months of fighting the spread of COVID-19, a number of protective measures have made their way into our daily routine: We wash our hands, sneeze into our arm, wear a mask, social-distance and elbow-bump. But another potentially crucial weapon in combatting the virus has gone underreported in many parts of the world: ventilating closed spaces.

Ventilation's biggest fan: Though the science is still divided, ventilation has moved to the center of government recommendations in a country respected for its pragmatism and scientific rigor: Germany.

Doing the heavy Lüften Among the lesser-known stereotypes about Germans is their love of fresh air. True to linguistic form, they even have a name for it: Stosslüften, or the act of airing a room several times a day. Thus her fellow Germans weren't surprised when Chancellor Angela Merkel herself advertised ventilating as "one of the cheapest and most effective ways" of containing the spread of the virus.

Germany's handy acronym against coronavirus, AHA (Abstand, Hygiene und Alltagsmasken: Social distancing, Hygiene and Facemasks) has recently gained two letters: enters AHACL, with C and L standing respectively for Corona-Warn-App, the government's prevention app, and Lüften — airing.

  • The update is based on the belief that "regular ventilation in all private and public rooms can significantly reduce the risk of infection," as Münich-based Merkur daily reports.

  • With winter around the corner, opening windows to fend off the pandemic is becoming less of an option. Germany's federal government is about to invest a half-billion euros in the renovation of ventilation systems in schools and public buildings, as German daily Die Welt reports.
    → The goal: retrofitting old AC systems so that they can use as little circulating air as possible, and as much outside air as possible, therefore avoiding recycling potentially contaminated air while limiting heat loss during cold months.

Open window in a classroom in Stuttgart, Germany — Photo: Christoph Schmidt/DPA/ZUMA

An idea is spreading: For months, evidence has been mounting that the virus can spread by microparticles and aerosols. At the beginning of October, the Centers for Disease Control and Prevention published guidelines on Oct. 5, declaring the novel coronavirus is indeed airborne. But Germany, it turns out, is not alone in pushing the merits of airing:

  • The Spanish government has issued an extensive series of specific guidelines "on the use of air conditioning and ventilation systems to prevent the spread of COVID-19" covering aspects such as airflow rates, humidity levels and the replacement of air filters. Another guide aimed specifically at the country's schools, recommends ventilating classrooms five to six times per hour — never mind lower outside temperatures, the guide going as far as to recommend students "wear warmer clothes", the Madrid daily ABC reports.

  • In the U.S., the craze surrounding high-end air filtration systems is "like toilet paper in April times two," CNBC quotes the CEO of a Texas AC company as saying, with HVAC (Heating, Ventilation and Air Conditioning) systems selling like hotcakes.

  • In France, "airing rooms for 10 minutes, three times a day" is now part of the country's mesures barrières to stop the spread, as shown on government website — a matter of particular importance for the French who have just entered their second nationwide lockdown.

  • Japan too, focused on ventilation, as sociologist Zeynep Tufekci writes in The Atlantic. The government has asked the population to stay away from places that may gather "the three Cs": Crowds, Closed spaces, close Contact.

The takeaway Airborne? Well, it's complicated. Although many questions about the pandemic remain open, according to Dr. Bill Schaffner, an epidemiologist at Vanderbilt University, the spread of coronavirus through aerosols is "rather uncommon." The virus, it seems, spreads mainly through direct contact and via droplets that are significantly bigger and therefore not subject to airborne transmission per se.

At the same time, as Tufekci writes, super-spreading events seem to overwhelmingly occur when three conditions are reunited: 1) many people 2) especially in a poorly ventilated indoor setting 3) and especially not wearing masks.

  • In other words, though COVID-19's airborne risks may be relative, ventilating efforts still make sense — that is, if done in conjunction with other prevention methods. Which means that for now, the best solution may rest not with the Germans, but with their neighbors: the Swiss cheese approach, where each holey slice of cheese serves as an additional barrier against the spread.


See more from Coronavirus here