If there is NO WIND (like lab conditions - probably not your stand), then scent travels more quickly in warm air simply because the molecules that make up air are moving faster on average. Scent in cool air spreads more slowly since the molecules, on average, are moving more slowly.

Cold air is more dense than warm air, but this doesn't have a whole lot to do with why scent spreads at a certain rate.

Of course, any kind of wind will dramatically (and directionally) speed up the dispersal of scent.

Nate