What is the black residue in the ceilings of old houses?

Question

The last one I opened up was a 2 story 75+ years old. This reside was in the cavity between the floor and ceiling. The residue is very black and dirty.

Answer 1

sounds like mold. I would call some kind of mold-detecting company in your area and explain it to them.

Answer 2

unfortunatly, it is the fallout of explosive directional diareaha. i would advise the use of gloves while cleaning it up.