Effect of indoor air changes on COVID-19 transmission

Editor's Note

In this JAMA Insights article, researchers from the Harvard School of Public Health, Boston, and University of Michigan, Ann Arbor, conclude that increasing air changes per hour and air filtration are simple concepts that could be used to help reduce within-room, far-field (ie, within-room but beyond 6 feet) airborne transmission of COVID-19.

Buildings have been linked to the spread of infectious diseases, such as measles, influenza, and Legionella, and the majority of COVID-19 outbreaks involving three or more people have been associated with time spent indoors. 

Most buildings, except for hospitals, operate at bare minimum standards for ventilation and filtration and are not designed for infection control. To reduce COVID-19 transmission in indoor spaces, such as classrooms, retail shops, and homes if guests are visiting, the target should be four to six air changes per hours.

This could be accomplished through a combination of:

• outdoor air ventilation
• recirculated air that passes through a filter with a minimum efficiency rating value (MERV) of at least 13
• passage of air through portable air cleaners with HEPA filters.

Despite the dose-response for COVID-19 being unknown, and continued scientific debate about the dominant mode of transmission, evidence supports these suggestions, the authors say.