Odor · no source found
A smell with nothing to point at
Whether this Pittsburgh line is the right call depends on where the smell leads. If it leads toward an attic, a crawl space, a garage or a hillside foundation void, a visit is worth it. If it leads toward a sealed interior wall and nothing else, it usually is not.
Working out where it actually is
Where it is strongest
Near an attic hatch, a crawl space access, a garage, or low against a wall on the downhill side of the house points at a reachable space.
Does the heating change it
If it sharpens whenever the furnace runs, the smell is travelling on moving air — through ductwork, or a cavity the warm air pushes past. Worth following that trail.
Insect activity
A cluster of flies at one window, vent or fixture usually sits close to the source.
What you heard before it went quiet
Scratching or movement in a ceiling or wall a week or two back, then silence, then a smell in that same area, narrows the room.
Recent sealing work
A capped foundation vent, a soffit repair, or a chimney cap installed not long ago can shut an animal in without anyone knowing.
When the trail ends at a finished wall
A small animal that dies inside a closed-up interior wall, with no attic or crawl space connection to reach it from, is not retrieved by cutting into the wall for this service. That is a construction job, not a carcass job.
What actually happens in that situation: the smell builds for a period, then fades as the animal dries out, on its own timeline. Nobody can hand you an exact number of days for that, and a page that does is guessing.
Rule out the plumbing first
An unused basement floor drain or a spare bathroom nobody runs water in produces a smell people routinely mistake for a carcass. Pour water down every drain in the place, wait a day, and see whether it lifts before spending money.
How these usually resolve
In a reachable space, which makes it an attic or crawl space recovery. Sometimes outdoors against a foundation or retaining wall, which is a pickup. Occasionally a deer that came down a hollow behind the house and was never seen. Cost covers why a search prices differently from a job where the animal is already found.