The velocity of an average air molecule at normal atmospheric pressure is about 1000 mph, so yes - brisk indeed. Of course the mean free path is only a few doze

The velocity of an average air molecule at normal atmospheric pressure is about 1000 mph, so yes - brisk indeed. Of course the mean free path is only a few dozen nanometers, so it'll take about 10^10 collisions before a molecule reaches that far - but they started with "a drop", or something like 10^21 molecules, so statistically there's plenty of opportunity for a few "lucky" molecules to make it - and it's so stinky that we can detect it even in those absurdly low concentrations.