Delayed Smells

Have you ever noticed that when you drive by a dead skunk it never seems to smell when you are right next to it? Or maybe a more pleasant smell would be burning leaves. It seems you can never smell them as you are passing through the cloud of smoke. Only after you drive down the road a bit can you smell them. Why is that? I’m sure there is a scientific explanation for it, but gosh darn it – I just don’t feel like looking it up.