By Joseph Allen OCTOBER 3, 2021SHARE (The Atlantic)
Before you read any further, take a long, slow, deep breath. Congratulations! If you’re sitting in a typical American home, office building, or school, about 3 percent of the air you breathed in recently came out of the lungs of the people in the room with you right now.
Breathing in one another’s air is kind of nasty when you think about it. We would never drink from the same cup of water that every one of our co-workers had just sipped out of. But something very similar happens all day long in our offices, schools, homes, buses, and even airplanes. All day, every day, we sit around breathing in what other people expel from their lungs. It’s the respiratory equivalent of drinking everyone else’s backwash.
The gross-out factor notwithstanding, inhaling someone else’s breath is not a big deal if they’re not sick. But if they’re actively infectious, they’re constantly releasing viruses packaged in small respiratory aerosols that form deep in the lungs.
How many pathogens you take in depends on one factor in particular: how much fresh air is coming into the building. Most buildings are poorly ventilated. But in a good building—that is, one designed to bring in significantly more outdoor air than building codes in the United States and elsewhere typically require—the proportion of indoor air that comes from other people’s lungs can be brought down to a level at which infection across the room is unlikely.