Stachybotrys

Definition

Stachybotrys chartarum is a greenish-black mold, often called "black mold" or "toxic black mold." It grows on materials with high cellulose content, such as the paper facing on drywall, ceiling tile and wood, and it needs those materials to stay wet over time, typically after a leak or water damage that was never dried. Many other common molds, including Cladosporium, Aspergillus niger and Alternaria, also look dark, so color and texture can't confirm that a patch is Stachybotrys.

Why It Matters

The name worries people, and the CDC's guidance is calmer than much of what's online. CDC says no test exists that proves an association between Stachybotrys chartarum and particular health symptoms, and that all molds should be treated the same with respect to potential health risks and removal. Some molds, Stachybotrys among them, can produce mycotoxins, and CDC's NIOSH says molds that produce mycotoxins should be considered the same as other molds that grow indoors. For some people, any mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or a skin rash, and people with asthma or a mold allergy may have more severe reactions. What Stachybotrys does tell you is something about the water: it points to material that has stayed wet, and finding and fixing that moisture is the job.

How It's Used in Mold Work

You usually don't need the species name to act. Routine spore-trap or microscopy analysis generally identifies a genus or broad fungal group rather than a species, and under ANSI/IICRC S520-2024, actual mold growth of any species is Condition 3 (Section B), so the remediation response is set by the material, the extent of the growth, the moisture, and how much disturbance the work takes, not by the species. Growth on chronically wet drywall or ceiling tile generally can't be cleaned back and has to come out, and cutting into that material without containment can spread it. Where a state licenses mold work, the license applies whatever the species.