The most dangerous molds
we identify in the field
A working reference on the five genera that cause the most harm when they show up indoors. What they look like, where they grow, and what they do to the people who are around them.
Stachybotrys chartarum (Black mold)
Where it grows: Damp cellulose. Wet drywall, ceiling tile, cardboard, paper-faced gypsum, wallpaper backing.
Why it's dangerous: Produces mycotoxins. Especially harmful to infants, the elderly, and immunocompromised people. Repeated exposure can lead to sinus congestion, persistent respiratory problems, chronic sore throats.
What we see in samples: Olive-black colonies; chain-arranged spores under microscopy.
Cladosporium
Where it grows: Carpets, wood, wallpaper, fabrics, HVAC components. Roughly 40 species, ranging from brown to green-black to gray.
Why it's dangerous: One of the most common indoor allergens. Heavy or prolonged exposure can progress to pulmonary edema and emphysema.
What we see in samples: Dark pigmented spores; chains visible under microscopy.
Penicillium
Where it grows: Damp wallpapers, carpets, fabric, food. Nearly 200 species; appears white, yellow, or blue indoors.
Why it's dangerous: Aggravates asthma, causes nail fungus, and in severe cases contributes to kidney, lung, and liver infections. Its presence indoors signals elevated humidity.
What we see in samples: Distinctive brush-like conidiophores under direct microscopy.
Fusarium
Where it grows: Cool, water-damaged fabrics and carpets. Grows at lower temperatures than most other indoor molds.
Why it's dangerous: Triggers asthma and allergic reactions. Acute exposure can cause respiratory illness, gastrointestinal symptoms, and (in chronic cases) reproductive-system impact.
What we see in samples: Orange or pinkish colonies; banana-shaped macroconidia under microscopy.
Aspergillus
Where it grows: Almost everywhere indoors. Around 200 species, yellow-greenish in indoor environments.
Why it's dangerous: Most species are benign for healthy people, but a subset (the "dirty 16") cause aspergillosis, respiratory tract infections and lung inflammation that are serious for immunocompromised patients.
What we see in samples: Genus identification by direct microscopy flags this one when it shows up at elevated levels indoors versus the outdoor reference.
Get it confirmed in our EMLAP-accredited lab
If you suspect any of the above, send us a sample or schedule field sampling. Genus-level reads are standard; species-level available where the case calls for it.
Need this analysis today?
Ship samples to our Union, NJ intake or schedule field collection. Standard turnaround 24–48 hours, rush available for wholesale partners.