Aju Business Daily

SEOUL -- Citizens in South Korea's southern port city of Busan feel safe without worrying much about droplet infection caused by coughing and sneezing when they use transit buses. Wearing masks is compulsory aboard intra-city buses installed with high-efficiency particulate air (HEPA) filters.

Busan with a population of 3.4 million is the first South Korean city to introduce HEPA-class filers for city buses. Masks also prevent droplet infection but HEPA filters are critical in preventing the spread of airborne bacterial and viral organisms from COVID-19 patients.

Common standards require that a HEPA air filter must remove more than 99.9 percent of particles whose diameter is equal to 0.3 μm. Modern airliners use HEPA filters to reduce the spread of airborne pathogens in recirculated air.