If you are breathing in the smell are you breathing in the bacteria or chemical?

Whenever you smell something, you are breathing in molecules called “odorants.” Those odorants come from whatever you are smelling, so you are always breathing in a part of that thing. This in itself is generally harmless. The problem is that odorants aren’t the only part of a thing that can become vaporized and make it into our lungs. That’s why it’s dangerous to mix ammonia and bleach, for example. It’s not the odorants that hurt us, but other parts of the resulting gas.

You mention bacteria and the odor from bacteria is from cellular respiration and odors are comprised of odor compounds that are the blue print for the odors perceived smell. These odor compound bind with receptors in the nasal cavity and this triggers a reaction in the brain that is what we have learned to be a particular odor. Interestingly the nasal cavity is a lot like our tongue that has distinct parts of the tongue dedicated to specific tastes, salty, sweet, sour etc so does our nose. Odor compounds are categorized by molecular composition and will have the specific smells we are familiar with. Esters are familiar to us in the form of sweet smells like banana or a flower. Amines are another familiar odor compound we all know as farts and fish. Then there are thiols that are things like garlic and natural gas. So we are not necessarily smell the “thing” but it’s odor compound(s) that is some form of cellular respiration or chemical reaction such as out gassing of a plastic polymer that we associate with that plastic smell of household items. Hope this helps.

Not exactly peer-reviewed,
but still relevant

Cleaning fluids and cleaning chemicals-
The smell you get is fumes, and they are all toxic in one way or another. I am allergic to them. Some of them make me quite ill.

The smell of rotting food from the bottom of a trashcan is a combination of waste by-products of bacteria, fungus, mold, and spores. Although I am allergic to fungus and mold, I rarely get a reaction as severe as I get from chemical fumes.

I imagine one is.
I’d be careful of breathing in the pest control fumes especially.Of course there are the class action suits against the makers of Round Up.
My brother has Non- Hodgkin’s Lymphoma because of that. The lawn care workers use it a lot in his neighborhood.

I forgot to mention Round Up is used for weed control.

I think my celiac-like symptoms are actually a sensitivity to glyphosate. Since I have no issues eating other types of gluten or wheat from Germany.

Yes.

Is it fumes if it’s days later?

If you can still smell it then yes.

Yes. The odiforus sensors in your nose, have to come in direct contact with the thing, you are smelling. So. Actual particles of the thing, are landing on those sensors. If you smell something, it’s because it literally entered your nose. If you smell shit, it’s because shit particles contacted your olfactory sensors. So. You have shit, in your nose…..