Info Hub · Mold Spore Library

A field guide to the molds living in Central Valley homes.

Mold is everywhere — outside, in dust, on your shoes. The question isn't whether spores exist in your home; it's whether something inside is letting them grow. Here's what we most often identify when we sample homes in Fresno and Clovis.

100,000+

Known species of mold worldwide

~10µm

Average size of a single mold spore

24–48 hrs

Time wet material needs to start growing mold

Common indoor genera

The species we identify most often.

None of this replaces lab analysis on your specific home — but it should give you a sense of what's worth looking into and what isn't.

"Black mold"

Stachybotrys chartarum

Where it hides: Persistently wet drywall, ceiling tiles, and wood after slow leaks or flooding.
Why it matters: Slow-growing and almost always tied to long-term water damage. Often associated with respiratory irritation in sensitive occupants. Requires moisture to thrive — fix the leak first.

Common indoor allergen

Aspergillus

Where it hides: HVAC systems, dust, insulation, and damp surfaces in nearly every home.
Why it matters: A large genus with many species. Generally harmless to healthy adults but can cause allergy symptoms and serious infections in people who are immunocompromised.

Blue/green colonies on food and walls

Penicillium

Where it hides: Water-damaged carpet and wallpaper, HVAC ducts, refrigerated foods.
Why it matters: Spreads quickly through indoor air. A frequent trigger for indoor allergy and asthma symptoms. Easily airborne, so it shows up in most air-sample reports.

Olive-green to brown spots

Cladosporium

Where it hides: Window sills, fabrics, painted surfaces, and HVAC condensation pans.
Why it matters: One of the most common indoor molds. Usually not toxic, but a known allergen that aggravates asthma and seasonal allergies.

Outdoor-origin allergen

Alternaria

Where it hides: Showers, sinks, under leaky windows, and on damp window frames.
Why it matters: Frequently enters homes from outdoors and settles in damp areas. A well-documented trigger for asthma and hay-fever symptoms.

Cotton-like, turning gray to black

Chaetomium

Where it hides: Chronically wet drywall, baseboards, and wood after long-term leaks.
Why it matters: Like Stachybotrys, almost always indicates a serious moisture problem. Has a distinct musty, damp odor that often gives it away before it's visible.

Pink, white, or red growth

Fusarium

Where it hides: Carpets and water-damaged fabrics after flooding events.
Why it matters: Grows even at lower temperatures, so it can spread in cooler rooms. Some species produce mycotoxins; can cause allergic reactions and eye irritation.

Bright white to deep green

Trichoderma

Where it hides: Wallpaper, carpet, and wet wood — anywhere persistently damp.
Why it matters: Fast-growing and aggressive on cellulose materials. Some strains are known allergens; chronic exposure can irritate the lungs and sinuses.

Educational summary only — not a medical or diagnostic resource. For health concerns related to mold exposure, talk to a qualified physician. For confirmation of species in your home, request a sample.

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