Are scents made up of tiny bits of the thing you're smelling?

I had a horrible realization the last time I was in a public restroom: What if the smells I’m smelling are made up of tiny bits of poo that are stuck to the air molecules that I’m inhaling. Is that what a scent is? When I smell the shit from the stall next door, are microscopic bits of poo going into my body?

If so, given a stagnant and non-functioning air circulatory system in the bathroom, how much time do I have from splashdown to detection do I have in order to get the hell out of there and avoid ingesting that otherworldly fecal matter?

The smell isn’t bits of crap floating around in the air. The smell is volatile chemicals that have evaporated from the crap. You know how you can smell a hot car engine because the oil? You aren’t smelling bits of car, just the volatile liquid that has evaporated. Same deal with crap. It’s not faeces you’re smelling, just some of the volatile liquids and gases that it contains.

But don’t rest to comfortably. Every time that a liquid splashes it forms an aerosol. An aerosol is literally a fine mist of of the liquid that floats about in the air. So when turd splashes into the water some of it does aerosolise, and you do breathe it in.

How long do you have to make a run for it? That depends on the barriers in place and any air currents, but anything from a few seconds to a few minutes. Because both the odour particles are smaller they diffuse faster than the aerosol, but unless the air is dead still if the smell has reached you then so has aerosol.

But don’t bother trying to run. Aerosols stay suspended for hours. Unless you’re the first person to use the facilities in the last four hours or so you start breathing in someone else’s crap as soon as you open the door.

I’m having trouble distinguishing between “crap” and “volatile chemicals that have evaporated from the crap”, and between “faeces” and “the volatile liquids and gases that it contains.”

Sounds to me like we’re inhaling everything but whatever solids may be there. Not much of a difference, as I see it.

Yes, it doesn’t seem comforting to know that you’re not snorting micro-turds, you’re just snorting volatile micro-turd chemicals…

Well, some of the smell is gases excreted by bacteria eating the poop.

Doesn’t that make you feel better?

As I said, when you smell a hot car engine, do you think that you are inhaling bits of the car? Technically you are because the volatilised oil is part of the car, but you are definitely not inhaling pieces of gearbox and pieces of steering wheel. That seems like a significant difference to me. YMMV, and maybe you do think that you are inhaling the car rather than simply the oil.

More importantly odour molecules are non-living and completely harmless in those concentrations. In contrast entire faecal particulates contain live, pathogenic bacteria. That’s not a trivial distinction.

Yes, the molecules that have entered your nose and excited your sensory apparatus originated inside someone else’s ass. So the fuck what? What possible harm could this do to you?

AFAIK all of the smell is gases and liquids excreted by bacteria eating the poop. If the material had only been digested using gut enzymes it would have very low and rather neutral odour, somewhat akin to wet cloth. The smell is entirely mercaptans and sulfides produced by bacteria.

IOW it’s all bacterial excrement. Fell better now?

It’s even worse: when you flush, the water sprays up an aerosol of tiny germ-filled droplets that you can’t smell.

Of course, it’s been happening your entire life, so you’ve got to figure it’s not really anything all that harmful.

That is why those things come with lids. Close the lid before you flush. Problem solved.

Obligatory Ice Storm reference.

Most public restroom toilets I’ve seen don’t.

This is indeed very clear. I thank you, and I hope no one thinks I’m being sarcastic. Thanks.

What problem? It’s been happening ever since the flush toilet was invented and we’re not overrun by E. Coli infections.

And there are rat droppings in most of the prepared food you eat, too. At low levels, it’s harmless. You’ve been eating it all your life with no ill effects.

Band name, or weapon of choice against our enemies.

A common fallacy.

The fact is that people die of faecal bacterial infections every day, and hundreds of thousands of people get ill. So saying that “it’s harmless” is based on a massive fallacy. It may be acceptable but it is not in any sense harmless.

We could say the same thing about washing your hands or thawing frozen food on the benchtop or a millionother provably unsafe practices. People do those things every day as well, and we aren’t overrun by the diseases they cause. Nonetheless they are all problems and cause significant illness and losses of productivity.

Eating rat droppings, not washing your hands, reheating food and flushing with the lid open are all practices with low risks of producing illness. I’d guess they all have about the same risk. That does not mean they are not problematic.


Say what? Reheating food is a health risk on a par with not washing your hands after using the restroom? Or “eating rat droppings” (which are trace amounts resulting from food storage in transit and have presumably been cooked, if not mostly washed away)?

On a molecular level, it’s all poo.

The same difference there is between smelling a steak and eating it. How much nourishment can you get from smelling the exhaust fan of a restaurant kitchen?

You are smelling the volatile compounds coming off the item you’re sensing.

But you’re also inhaling lots of particles from these items, too. Items small enough to be aerosolized and drift up your nose and into your eyes and mouth, but too large to affect the olfactory bulb in the head. This includes bits of fat, protein, and carbon scoring from steaks as well as flecks of undigested food and bacteria from stool.

Fortunately the number of bacteria tends to be too small to start infections successfully. Usually.