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Allergenic and a water-damage indicator. Some species produce mycotoxins (trichothecenes, fumonisins) that can cause more serious health effects; rarely opportunistically pathogenic in immunocompromised patients.

Where it's found

Water-damaged carpet, drywall, and wallpaper; also soil and plant debris carried indoors. Often appears after a flood or sustained slab moisture.

What it looks like

Pink, white, salmon, or red-orange colonies; cottony or wool-like texture; fast-growing.

Triggers hay fever, asthma, and allergic fungal sinusitis. In immunocompromised patients can cause cerebral abscess, keratitis, or pneumonia. Saprotrophic on dead plant material outdoors.

Where it's found

Damp paper, wood products, and fabrics indoors. Outdoors: dead plant material and soil. Indoor presence often signals chronic humidity, not flooding.

What it looks like

Greenish-black to dark olive colonies with woolly or velvety texture; curved (banana-shaped) spores under the microscope.

Allergy trigger associated with allergic fungal sinusitis and asthma. In rare immunocompromised cases can cause cerebral or pulmonary infection. Primarily an outdoor plant pathogen.

Where it's found

Plants, soil, decaying organic matter outdoors; indoors usually reflects dust and outside-air infiltration. Reported on most Florida spore-trap panels.

What it looks like

Dark grey to black colonies, velvety surface; long banana-shaped (bipolar) spores.

Primarily a plant pathogen rather than an aggressive indoor invader. Spores are allergenic — chronic exposure has been linked to "winegrower's lung," a hypersensitivity pneumonitis, and can trigger asthma in sensitized people. Generally not opportunistically pathogenic in healthy adults.

Where it's found

Decaying fruit, vegetables, and houseplants brought indoors; occasionally damp cellulose materials. Florida humidity makes stored produce a reliable indoor spore source. Best known outdoors as the "gray mold" of strawberries, grapes, tomatoes, and ornamentals.

What it looks like

In culture: gray-brown fuzzy mycelium with visible sporulation patterns across the agar surface. On host plants: a grey dusty fuzz over softened tissue that releases visible spore clouds when disturbed.

Common allergy trigger — hay fever and asthma. Generally not opportunistic; produces minimal toxins. Found everywhere outdoors so background indoor levels are normal.

Where it's found

Plant material, soil, paper, textiles. Outdoor air everywhere; elevated indoor counts suggest outside-air infiltration or contaminated cellulose materials.

What it looks like

Yellow-orange to red-brown colonies with cottony or woolly texture; mature colonies darken to deep brown.

Major outdoor allergen during summer and fall spore release. Indoor presence usually means contaminated woody material or hidden wood-decay fungi reaching structural framing.

Where it's found

Decaying hardwood, tree stumps, sometimes structural wood behind sheetrock if hidden moisture has reached framing.

What it looks like

Large brown shelf-like fruiting bodies on trees ("artist's conk"); spores produce visible brown powdery clouds in late summer.

Generally non-allergenic but fast-growing and visually alarming. Can cause invasive mucormycosis in severely immunocompromised patients (especially diabetics). Sometimes called "bread mold" or "pin mold".

Where it's found

Bread, fruit, damp carpet, water-damaged building materials. Frequently the first organism to colonize after a flood — can cover surfaces overnight.

What it looks like

White to grey cottony fuzz that explodes in size within 24-48 hours; matures to black as spore-producing pin heads form.

A water-damage indicator. Some species produce mycotoxins; can cause persistent nail infections (onychomycosis) and rarely systemic infections in immunocompromised patients.

Where it's found

Water-damaged drywall, mattresses, wallpaper. Often grows behind cabinets, under bathroom flooring, or inside walls with chronic leaks.

What it looks like

Cream to light brown granular colonies; ages to a powdery tan, grey-brown, or olive surface.

Primarily an outdoor allergen (asthma trigger). Some species produce sporidesmin, a mycotoxin causing facial eczema in livestock; human exposure is mostly via dust inhalation, not indoor growth.

Where it's found

Pasture grass, dead leaves, decaying plant debris outdoors. Indoor presence usually reflects outside-air infiltration; rare on building materials.

What it looks like

Dark olive to black colonies with a velvety texture; conidia are dark brown, warty, and football-shaped under the microscope.

Allergenic — large spores can trigger asthma flares. Not pathogenic to humans. Technically not "true" molds (they're protists), but reported on standard spore-trap panels.

Where it's found

Decaying wood, mulch, leaf litter outdoors. Indoor presence is rare; sometimes seen on damp basement wood or along condensation paths near windows.

What it looks like

Vivid orange, yellow, pink, or red gelatinous masses that mature into dark spore-producing fruiting bodies; can creep slowly across surfaces.

Outdoor allergen — heavy spore release during plant-disease outbreaks. Not pathogenic to humans. Never grows indoors; an indoor reading reflects outside-air infiltration only.

Where it's found

Living plants outdoors — wheat, grass, roses, cedar, beans. Spores carry on wind currents into homes through windows and HVAC intake.

What it looks like

Orange-red powdery pustules on leaves and stems; individual spores microscopic and rust-orange in color (hence the name).

Allergy trigger — a major component of outdoor air spore loads, peaking in summer and fall. Some genera linked to hypersensitivity pneumonitis ("farmer's lung", "humidifier lung").

Where it's found

Outdoors: forest floors, wood-decaying fungi, mulched gardens, lawns. Indoors: indicates hidden wood-decay fungi behind drywall, in crawl spaces, or in attics with active moisture.

What it looks like

Source bodies are macroscopic — mushrooms, shelf fungi, puffballs. The spores themselves are microscopic and vary in color (white, brown, black, pink).

Allergenic — common component of outdoor air, peaks after rain. Many environmental species, a few opportunistic pathogens. This grouping covers spores from a vast phylum of fungi.

Where it's found

Forest floors, decaying plant material, soil, water-damaged paper. Many indoor molds (Stachybotrys, Chaetomium, Penicillium, Aspergillus) belong to this phylum.

What it looks like

Source bodies range from microscopic asci to visible fruiting bodies like cup fungi, morels, and the bright orange Cordyceps shown here.