How much of the air you’re breathing is air someone else exhaled, asks Newshub? And in the midst of a pandemic caused by an airborne virus, where are the riskiest places to be? On a full bus, the equivalent of one in every seven breaths is air other people are breathing out. Covid-19 aerosol particles are breathed, coughed or sneezed out by infected people. These can drift several metres and linger in the air for hours. “You can think of it as spit particles [that] you are breathing in,” says University of Auckland aerosol chemist Dr Joel Rindelaub. “It’s breath backwash that gets people infected.”