How dangerous is the air around us? | COVID-19 Special

Scientists are still assessing how dangerous these doses of airborne virus can be - and what we can do to avoid them. Opening a window is one way to keep the air fresh. That's a bit more complicated in the winter, doesn't work in all rooms, and certainly doesn't work on airplanes. The aviation industry says cabin-air is sufficiently filtered and circulated. Some experts say questions remain. But by keeping the air moving with systems like air conditioning, are we decreasing the risk, or merely spreading it?