Modern people spend about 90 % of their time indoors, and the U.S. Environmental Protection Agency notes that indoor pollutant concentrations can be two to five times higher than outdoor levels.
This problem is especially acute in hospitals and clinics. According to the World Health Organization, in high-income countries, seven out of one hundred hospitalized patients acquire at least one healthcare-associated infection, while in middle- and low-income countries this figure reaches fifteen out of one hundred.
According to World Health Organization estimates, in 2021 household air pollution caused 2,9 million deaths, more than 309 thousand of which were among children under five years of age.