I came across this today in a house with a solid amount of rodent activity in the crawl. I figured it may be a clue for some other inspectors.
I have not ever seen his, but the seller had several had several cabinets with bare charcoal (burnt wood chunks) in the cabinets. Apparently, this is some sort of a prevention of mice and or rats as they do not like the smell according to the good ole’ interweb! So (Lesson learned), if you see random charcoal chunks by the range hood and in lower cabinets, the seller is trying an old school method of preventing them from further access. I see lots of rodents in my area, but this was a new one for me. No guarantee of function as rodents were present in the crawls and active, so it does not seem to work for long if at all!
Probably for moisture control. I guess!
Uncle Ernie’s femur. 
Never trust a seller…just saying…
Good one Jordan & true.
They could have forgone the mess & used mothballs.
If they’re hungry enough they’ll get used to it.
Mothballs work. The way to keep them separate from food is to place the mothballs in baggies with small holes. The odor escapes but the mothball cannot make contact with the food containers, Important locations are under the sink stove and cabinets.
That green chew poison inside a little plastic box works best (forget the brand) Mice eat the poison and it dehydrates them so they go outside looking for water (last thing I want is dead mice in the house).
Bob that green stuff is a paraffinized bait block, it helps it from getting moldy/rotted so there’s a better chance of acceptance.
The active ingredient is usually Diphacinone that inhibits vitamin K.
It will take 5-7days of continuous feeding for it to finally kill Willard.
Poor little guy then hemorrhages to death.
The reason it is popular is in case of an accidental feeding (child, dog) one hit is not enough to cause a problem 
The running outside to search for water is a myth.
Doctor Marc! I didn’t know, how come they never croak i the house? The water thing the rodent guy told my daughter when that farmhouse of hers was overrun. She finally got a cat. Best mouse control possible.
Hey Marc,
Mothballs may not be a good idea.
Don’t know why.
Most indoor rodent control is with live or snap traps.
The poison gets 'em outside.
Willie died when trying to seal one of my cards.
Why not?
Naphthalene is good stuff.
Got a good beat, easy to dance to, I’d give it an eight… … …
I just killed a rat in my crawl space with a snap trap. A few days before, his brother caught his leg in it but got away….without his front foot.
I’ve used poison before but with pex piping I usually end up having to crawl under to fix leaks made by the thirsty buggers,
Hard to argue with that! 
The permissible exposure limit for naphthalene used to be 10 ppm.
At 250 you have a problem. I think you can still buy them here but not some other countries.
You can buy them in the drugstore here, but they werent much use in trying to keep the moles out of my egress window well…
Try Frank’s Hot Sauce or tar
Hot sauce will deter them ???
since it is a basement egress window I rarely go past it, about every 4 to 6 weeks I usually find a few corpses to remove, always moles or frogs, can’t imagine what makes them want to jump in there ,but once in they never seem to find a way out…
Sure - for a while… … …
After they get used to it they will just avoid the area - for a while… … …
Behavioral resistance - I have it for my ex-wire!
didn’t work on either of my exe’s…perhaps a different kind of rodent…
For moles you can set a mouse or rat trap.
You’re gonna have to bait it with worms though.