system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If the smell from something can reach your nose, does that mean that you are being exposed to bacteria from that thing?
gpt
Not necessarily, and in fact, not usually. 

Our noses are sensitive and only a small number of airborne molecules  can give it enough information to "smell" something. We can smell forest fires from miles away as an example.

But light molecules like that are very very easy to carry around in the air. Bacteria are composed of billions of those molecules jammed into an organism, and they aren't. And most of them are not designed to be removed from a surface and blown around anyway - they transmit around more by touch or by being carried around on dust or in raindrops or sneeze particles or on the feet of flies or stuff like that.

So the odds that you're breathing bacteria from that dead skunk on the side of the road that you've just driven by are very slim unless you go right up to it and breathe in a big nostril-ful.  (You could try it if you wanted.)