[Reading Science] Clean 'Indoor Air' Prevents the Second Pandemic

Belgium, USA, UK Strengthen Indoor Air Regulations
COVID-19 Virus Major Transmission Route is 'Indoor'
Prevent Future Pandemics and Various Diseases like Lung Cancer, High Cost-Effectiveness

Since the COVID-19 pandemic highlighted the importance of indoor air quality, countries around the world have been strengthening regulations. Although funding remains an issue, analyses suggest that installing indoor ventilation systems that simultaneously purify and sterilize the air can yield significant benefits relative to the investment.

According to the international scientific journal Nature, major countries such as Belgium, the United States, and the United Kingdom are tightening indoor air quality regulations to prevent future pandemics. Belgium has mandated that from July, indoor air quality in public places such as pubs and bars must be maintained at a certain level, with real-time display of carbon dioxide concentrations so that anyone can verify it. From 2025, gyms, restaurants, and indoor workplaces will also be required to install indoor air quality measurement and display systems. In the event of another pandemic, the presence of such systems will be a criterion for deciding whether to close facilities. Belgium enacted this law in July last year based on the judgment that improving indoor air quality is essential to prevent and manage highly contagious respiratory diseases like COVID-19 and influenza.

Reference photo. An elementary school classroom equipped with an air purifier.

The U.S. government also launched a program in March last year encouraging building owners and operators to improve indoor air quality and ventilation facilities. In October last year, California passed a bill mandating the installation of indoor air purifiers in all school buildings. Two months later, the White House announced measures to ensure that approximately 1,500 federally owned buildings meet minimum indoor air quality safety standards. In the private sector, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) announced it will establish technical standards to reduce indoor infection risks by June this year, spurring active facility improvement and management enhancement efforts. The recommendations set by this society are required to be followed not only in the U.S. but also in several other countries. The gas stove usage regulation controversy that arose in the U.S. at the end of last year originally stemmed not from a progressive-conservative conflict but from discussions on improving indoor air quality. In the U.K., major engineering institutions released a report in June last year, supported by the government, calling for mandatory measures to ensure air quality safety throughout the lifespan of buildings.

This movement to improve indoor air quality was triggered after the COVID-19 pandemic because the virus spread mainly in indoor spaces, similar to measles, tuberculosis, and seasonal flu. Health authorities worldwide, including the World Health Organization (WHO), were initially unable to make early judgments about airborne transmission. It was only in March 2021 that WHO issued official guidelines.

Recent studies have increasingly shown that improving indoor air quality greatly helps prevent infectious diseases. A study conducted in the Marche region of Italy on about 10,000 school classrooms found that in 316 classrooms equipped with exhaust systems supplying 1.4 to 14 liters of fresh air per person per second, the COVID-19 incidence rate over four months decreased by at least 74% compared to classrooms with only window ventilation. The effect was greater with increased fresh air supply. When ventilation reached at least 10 liters per person per second, infection rates dropped by over 80%.

Air purification technology has also made significant progress recently. One study showed that running two air purifiers equipped with high-efficiency particulate air filters in a 54-square-meter conference room with three mannequins reduced the probability of exposure to aerosols capable of transmitting COVID-19 by up to 65%. This effect was comparable to all three mannequins wearing masks, which reduced exposure by 72%. Additionally, research from the Catholic University of Leuven in Belgium found that combining air purification and ventilation achieved an effect equivalent to six air changes per hour. Aerosol concentrations were reduced to 5-10% of levels observed without any ventilation measures.

However, challenges remain. Retrofitting schools, offices, and public spaces with air purification facilities involves enormous costs. Nevertheless, experts argue that the benefits far outweigh the expenses. For example, in the U.K., the social costs of the COVID-19 pandemic and seasonal flu amount to an average of $27 billion annually, and improving indoor ventilation systems alone could save approximately €174 billion over 60 years, according to expert analyses. Moreover, improving indoor air quality reduces exposure to fine dust generated by fires or cooking, volatile organic compounds emitted from furniture, and allergens such as mold and pollen. This helps prevent various respiratory diseases, including lung cancer, and allergies. However, increased energy costs and carbon dioxide emissions remain challenges to be addressed.