Black mold is the common name for Stachybotrys chartarum, a greenish-black mold that grows on paper-faced drywall, wood and ceiling tile that stay wet for a long time. Many unrelated molds are also dark, and color cannot identify a species. A laboratory can: a surface sample taken with tape or a swab is examined under a microscope, and the report names what is growing. The more important finding is usually the one beside it — why that material has been wet long enough for it to grow.

  • Surface sampling of visible growth for laboratory identification
  • Air sampling to check whether spores have spread
  • Moisture readings and thermal imaging to find the water source
  • Inspection behind and around the affected area
  • Written report naming the molds found and recommending next steps

Does the type of mold matter?

For deciding what to do, usually not. The CDC's position is that it is not necessary to identify the type of mold in a home, because all indoor mold growth should be treated the same way: remove it and fix the moisture. Health effects from mold exposure — congestion, coughing, wheezing, eye and skin irritation, and worse symptoms for people with asthma, allergies or weakened immune systems — are associated with mold in general, not with one species.

Identification is useful for other reasons: documentation for a landlord, insurer or sale; reassurance about what a growth is; and as a clue to conditions, since Stachybotrys indicates prolonged wetness and not a brief spill.

What about mold toxicity?

Search results are full of lists of warning signs of mold toxicity, and they deserve a careful answer. Some molds can produce mycotoxins, and damp, moldy buildings are linked to respiratory symptoms and worsened asthma. Claims that go further — that a home test or a urine test can diagnose a specific mold illness — are not supported by mainstream medical guidance. If you have health concerns, see a physician and describe the conditions in your home. A building inspection can establish whether there is a mold and moisture problem to fix; it cannot diagnose a person.

After a positive result

A small patch on a hard surface can often be cleaned by the occupant. EPA guidance uses about ten square feet as the rough line above which professional remediation is advisable, and any size where mold is in the heating and cooling system or follows sewage or flood water. Remediation should be done by a company separate from the one that tested, and clearance testing afterward confirms the result.

Common black mold testing situations in Santa Clarita

  • Dark spotting on drywall near a leak
  • Black growth on a ceiling below a bathroom or roof leak
  • Dark mold behind furniture on an exterior wall
  • A landlord or seller disputing whether a stain is mold
  • Worry about what a growth is before disturbing it

Keep in mind: Do-it-yourself petri-dish kits are of little use. Mold spores are in all air, so a plate left open will almost always grow something. The result does not tell you whether you have a problem or where it is.

Black Mold Testing FAQs

Can I test for mold myself?

You can buy a kit, but the results are hard to interpret. Settle-plate kits grow whatever lands on them and have no outdoor comparison. A swab of a visible growth sent to a lab will name the mold, which rarely changes what needs doing. A professional inspection adds what a kit cannot: locating the moisture source.

What should I not do with mold I find?

Do not dry-scrape, sand or vacuum it with an ordinary vacuum, which spreads spores. Do not paint over it. Do not mix bleach with ammonia or other cleaners. And do not simply clean it and leave the moisture problem in place, because it will return.

This content is reviewed by the Santa Clarita Mold Testing editorial team and informed by licensed-contractor sourcing, manufacturer documentation, and established industry standards for Mold Testing. Read our editorial standards.