What it is
Stachybotrys chartarum is the species most people mean when they say 'black mold.' It's dark green to black, has a slimy or wet appearance when fresh, and almost always indicates that a building material has been wet for an extended period - weeks, not days.
Where it grows
On cellulose-rich materials kept consistently wet: paper-faced drywall, wood, cardboard, ceiling tile, and the back side of wallpaper. It's the species we most often find behind kitchen and bathroom drywall where a slow leak ran undetected.
Health impact
Produces mycotoxins linked to respiratory irritation, sinus inflammation, headaches, fatigue, and stronger reactions in sensitive individuals - asthma sufferers, infants, elderly, immunocompromised. Health effects from short-term exposure to mild colonies are usually irritation; chronic exposure to active colonies is the bigger concern.
This species produces mycotoxins. That matters because mycotoxins can affect indoor air quality even after visible mold is gone - they ride on dust particles and require thorough removal, not just surface cleaning.
Property risk
Stachybotrys digests cellulose, which means it's actively breaking down structural drywall, framing, or substrate while it grows. A confirmed colony often means the affected material needs to come out, not just be treated.
When to test
If you see what looks like stachybotrys (black mold) in your home - or if a lab report flagged it in your air samples - testing the affected area against an outdoor baseline is the most useful next step. The decision about remediation depends on:
- How much is present (spore count per cubic meter, or visible square footage)
- What's beneath it (porous materials like drywall and insulation usually need removal; hard surfaces can often be cleaned)
- Whether the moisture source is identifiable and fixable
Our approach
For confirmed indoor stachybotrys (black mold) colonies, our process is the same as for any mold species: identify and stop the moisture source, contain the work area, remove what's compromised, HEPA-filter and HEPA-vacuum the surrounding area, dry everything, and verify with a post-remediation clearance test against the outdoor baseline.