As colder months set in, respiratory infections begin to climb: everything from the common cold and flu to COVID. It’s a time when healthy lungs matter more than ever. Yet the very tissue that lets oxygen pass from air to blood is remarkably delicate, and habits such as vaping can weaken it just when protection is most needed. The lungs are often pictured as two simple balloons, but their work is far more intricate. They act as a finely tuned exchange system, moving oxygen from inhaled air into the bloodstream while releasing carbon dioxide produced by the body’s cells...