“Black mold” usually means Stachybotrys, a greenish-black mold that grows on chronically damp, porous surfaces. You can’t confirm the species by eye, but a few signs reliably point to a problem worth investigating.
What to look for
- A persistent musty, earthy smell — often the first sign, before you see anything.
- Dark green-to-black patches that look slimy or fuzzy, especially on drywall, ceilings, or around plumbing.
- Water history — a past leak, flood, or condensation problem in the same spot.
- Symptoms that ease when you leave — congestion, cough, or irritation that improves away from home.
Don’t disturb it
Scrubbing suspected black mold sends spores airborne. For anything beyond a small surface patch, contain it and call a pro.
Is it actually mold?
Surface stains are sometimes just mildew, which is cheaper and easier to handle — see mold vs mildew to tell them apart.
What removal costs
Black mold costs more to remove than common mold because of containment and disposal. Get a ballpark with the black mold removal cost calculator before you call anyone.