Los Angeles County · Black mold testing
Black Mold Testing in Los Angeles
You can’t identify black mold by color. Most dark spots in LA homes are common molds like Cladosporium, not Stachybotrys. A tape lift or swab sent to an accredited lab tells you the species within a few days. Typical Los Angeles cost: $75–$150 per sample, or $400–$800 with an inspection and air samples.
- Emergency24/7 response
- CoverageAll of Los Angeles County
- LabAIHA-LAP accredited analysis
- StandardANSI/IICRC S520
- Call(213) 659-0672
The basics
Is it black mold, or just dark mold?
“Black mold” usually means Stachybotrys chartarum, a greenish-black mold that grows on materials that have stayed wet for a long time. But many molds look black. Color, smell and texture can raise or lower suspicion. Only a lab can confirm the species.
Black mold is worth taking seriously, but the fix is the same for any mold growing indoors: find the moisture source, remove what’s damaged, and verify the result. The CDC and EPA say you usually don’t need to know the species to clean it up.
| Mold | What it often looks like | Where it shows up in LA homes |
|---|---|---|
| Stachybotrys chartarum | Greenish-black, slimy when wet, sooty when dry | Drywall paper, ceiling tiles and wood that stayed wet for weeks: slow leaks, roof leaks, flooded walls |
| Cladosporium | Black, olive or dark green speckles | Shower caulk, window frames, bathroom ceilings; very common near the coast with the marine layer |
| Alternaria | Dark gray to black, fuzzy | Window sills, damp carpet, areas near sinks |
| Aspergillus niger and other Aspergillus | Black, green or yellow, powdery | Dust, HVAC parts, damp building materials |
| Chaetomium | Starts white, turns gray to olive-black | Water-damaged drywall and wood, often alongside Stachybotrys |
Appearance is a clue, not an answer. Several of these can grow side by side on the same wall.
Sampling methods
How do you test for black mold?
Black mold is tested with surface samples taken from the growth itself, usually a tape lift or swab, sometimes a small bulk piece of material. Air sampling adds context about what’s in the air you breathe, but it can miss Stachybotrys, so surface samples are the main tool when you can see the growth.
Tape lift
Clear tape pressed on the growth, then sealed on a slide. Fast, cheap and good for identifying the mold on a flat, dry surface like drywall or a cabinet back.
Swab
A sterile swab rubbed across the area. Better for wet, slimy, rough or curved surfaces where tape won’t stick, such as framing, pipes or corners.
Air sample
A pump pulls air through a spore trap cassette, indoors and outdoors. Helps find hidden growth behind walls or in a crawl space.
For hidden mold, we find wet areas with a moisture meter and thermal imaging first. Learn more about mold air quality testing.
Lab confirmation
How does a lab confirm Stachybotrys?
A lab analyst looks at the sample under a microscope and identifies mold by the shape of its spores and structures. Results usually come back in 24 to 72 hours. Use a lab accredited through AIHA-LAP’s EMLAP program, and make sure every sample travels with a chain of custody form.
- What the report shows: the mold types found on each sample and how heavy the growth is (often rated as rare, low, moderate or heavy).
- For air samples: spore counts per cubic meter for each type, side by side with the outdoor control.
- Chain of custody: a signed record of who took each sample, where and when. It’s what makes a report hold up with a landlord, insurer or buyer.
Should you test?
When is black mold testing worth paying for?
Testing is worth it when the result changes what you do: proving a problem to a landlord or insurer, checking a home in escrow, finding hidden growth, or protecting someone with asthma or a weak immune system. It’s usually not worth it for a small patch you can see and clean.
| Your situation | Test? | Why |
|---|---|---|
| Small patch (under about 10 sq ft) on a hard surface, cause is obvious | Usually no | Clean it and fix the moisture. The species doesn’t change the cleanup. |
| Dark growth on drywall after a leak or storm | Often yes | Confirms what’s there and helps set the scope of removal. |
| Musty smell, no visible mold | Yes | Moisture mapping plus air samples can locate hidden growth. |
| Renter whose landlord won’t act | Maybe | A free city or county code inspection comes first. Lab testing adds documentation for a dispute. |
| Buying or selling a home | Yes | An independent report helps both sides negotiate within the contingency period. |
| Someone in the home has asthma, allergies or a weak immune system | Often yes | Gives you and your doctor facts instead of guesses. |
Renters: you don’t need our test to file a complaint. In the City of Los Angeles, call LAHD at (866) 557-7368. In unincorporated areas and most County cities, call LA County Public Health Environmental Health at (888) 700-9995. See who to call about mold in your city and our guide to black mold in an apartment.
Pricing
How much does black mold testing cost in Los Angeles?
A single lab-analyzed surface sample typically costs $75–$150 in Los Angeles. A visit with an inspection, moisture mapping, two or three air samples and an outdoor control usually runs $400–$800. The final price depends mostly on how many samples the home needs.
| Service | Typical LA range |
|---|---|
| Visual inspection with moisture mapping | $250–$500 |
| Inspection with 2–3 air samples plus outdoor control | $400–$800 |
| Each additional tape lift, swab or air sample | $75–$150 |
| Post-remediation clearance test | $300–$600 |
Typical industry ranges for the Los Angeles area. Your written quote depends on the size, access and number of samples involved.
Crawl space or attic access, rush lab turnaround and a third-party report can add to the cost. See our mold inspection cost guide for Los Angeles. You get the price before we take a sample.
Next steps
What should you do with black mold test results?
Whatever the species, the plan is the same: stop the water, remove or clean the growth at the right containment level, then confirm it’s gone. A positive Stachybotrys result mostly changes how carefully the work is done and how well it’s documented, not whether the work is needed.
- Don’t disturb it. Scraping or sanding releases spores.
- Find the moisture source. A slow plumbing leak, roof leak, AC condensate line or slab leak. Mold returns if the water does.
- Get a written scope and quote. Small surface growth may be a cleaning job. Growth in drywall or insulation usually means removal under containment, following IICRC S520. Read more on how black mold removal works.
- Keep the paperwork. The lab report, photos and dates support a landlord notice, insurance claim or disclosure.
- Verify the work. After removal, an independent post-remediation clearance test confirms the area is clean and dry before walls are closed.
We recommend that the company testing your home is not the one selling the removal. Our guide to hiring an independent mold inspector explains why. If symptoms are a concern, talk to your doctor and share the lab report.
FAQ
Black mold testing questions
How can I tell if it’s black mold?
You can’t tell for sure by looking. Stachybotrys is greenish-black and slimy when wet, but Cladosporium, Alternaria and Aspergillus can look just as dark. A tape lift or swab analyzed by an accredited lab is the only way to confirm the species.
Is black mold more dangerous than other mold?
Stachybotrys can produce mycotoxins, and any mold can trigger allergies or asthma in sensitive people. The CDC says all indoor mold should be removed the same way, whatever the type. If you have symptoms, talk to your doctor.
Do I need to test mold I can already see?
Not always. For a small patch with an obvious cause, cleaning and fixing the moisture is enough. Testing helps when you need documentation, when the growth is large or inside walls, or when someone in the home is at higher health risk.
Are home black mold test kits accurate?
Not very. Petri dish kits grow whatever spores land on them, and every home has some, so they nearly always show mold. They can’t measure how much mold there is, where it is, or how indoor air compares with outdoor air.
Can my landlord test for black mold instead of me?
Yes, but a test arranged by the landlord may not be independent. In the City of Los Angeles, LAHD inspects for free, and visible mold can be a substandard housing condition under California law. This isn’t legal advice; contact Bet Tzedek or a tenant lawyer.
What happens if the test confirms Stachybotrys?
Fix the moisture source, then have the damaged material removed under containment following IICRC S520. Afterward, a clearance test by someone independent of the remover confirms the area is clean before rebuilding.
Sources
- U.S. Environmental Protection Agency (EPA), mold resources: epa.gov/mold
- Centers for Disease Control and Prevention (CDC), mold: cdc.gov/mold
- LA County Department of Public Health, Environmental Health: publichealth.lacounty.gov
- Los Angeles Housing Department (LAHD): housing.lacity.gov
- ANSI/IICRC S520, Standard for Professional Mold Remediation
Last updated October 2026. Prices are typical Los Angeles ranges, not quotes. Health information is general; talk to your doctor about symptoms. Back to mold inspection and testing in Los Angeles, or see apartment mold testing.
Want to know if it’s really black mold?
Call (213) 659-0672, 24/7 across Los Angeles County. We’ll tell you if testing is worth it before you pay for anything.