Lab-Backed Florida Mold Guide

The 7 Most Common Molds Found in Florida Homes

These are the seven mold species and species groups that appear in nearly every Florida air sample report I review. Most are background noise. One of them is the call I make at night. Here is how to read the list, what each species means for your home, and which one to take seriously.

By Jefferson Prada, Florida Licensed Mold Assessor (MRSA #3958)

How to Read a Florida Air Sample Report

When an AIHA-accredited laboratory analyzes an air sample from a Florida home, the report comes back with a list of fungal genera, a spore count for each one, and an outdoor control sample taken at the same visit. The number on the page only matters in relation to the outdoor baseline. A high count outdoors and a similar count indoors is normal. A low count outdoors and a high count indoors is a finding.

Almost every report includes the same seven species or species groups. Knowing what each one means and how it should behave relative to the outdoor sample is the difference between panic and a defensible conclusion.

The 7 Species, One by One

Species 1

Aspergillus / Penicillium

The two most common molds on the planet, reported together because they look nearly identical under a microscope.

Where it lives: Soil, old food, dust, HVAC systems, anywhere with low-grade humidity.
Indoor vs outdoor: Almost always present in both samples. The question is the ratio.
When to take it seriously: When indoor counts run 3x to 10x higher than the outdoor baseline. That gap usually points to a hidden moisture source feeding growth somewhere in the building envelope.

Species 2

Cladosporium

The outdoor mold by default. Lives on leaves, grass, exterior surfaces. Drifts indoors constantly.

Where it lives: Outdoors year-round in Florida, especially after rain. Indoors near leaks, window seals, AC drip pans.
Indoor vs outdoor: Outdoor counts are usually higher. Indoor should track below or near outdoor.
When to take it seriously: Indoor counts that exceed outdoor by a meaningful margin point to envelope failure: roof leaks, failed window flashing, condensation behind drywall.

Species 3

Alternaria

The allergy champion. Drives sneezing, watery eyes, asthma flare-ups in sensitive occupants.

Where it lives: Plants, dust, lightly damp spots like under sinks or in bathrooms.
Indoor vs outdoor: Low background indoors is normal. Elevated indoor counts often correlate with bathroom moisture or houseplant overload.
When to take it seriously: Symptoms in children, elderly, or asthmatic occupants combined with measurable indoor Alternaria counts. The species is rarely toxic but heavily allergenic.

Species 4

Basidiospores and Ascospores

Two large spore groups reported together. Basidiospores cover mushroom-type fungi; Ascospores cover sac fungi including many wood-decay species.

Where it lives: Outdoors year-round. Indoor presence rises sharply after rain, near wood decay, or in crawl spaces with chronic moisture.
Indoor vs outdoor: Outdoor reference is usually high. Indoor elevated above outdoor signals wood decay or rotting structural elements.
When to take it seriously: Sudden indoor spikes after a roof leak, plumbing event, or hurricane. Often the first lab marker of hidden structural damage.

Species 5

Stachybotrys

The one people call "black mold." Real, sometimes hazardous, but heavily misrepresented in marketing.

Where it lives: Cellulose materials soaked for days: drywall paper, wood, cardboard. Needs sustained moisture, not surface humidity.
Indoor vs outdoor: Should be effectively zero indoors and zero outdoors. Any indoor count is a finding.
When to take it seriously: Any spore count in the indoor sample triggers a same-day call to the homeowner. Indicates chronic, prolonged water intrusion that has fed growth on cellulose materials.

Species 6

Curvularia

Tropical and subtropical mold, common in Florida outdoor air.

Where it lives: Soil, plants, grasses. Outdoor air in Florida year-round.
Indoor vs outdoor: Outdoor background. Indoor counts that exceed outdoor suggest air intrusion or HVAC ductwork that pulls outdoor air through unconditioned spaces.
When to take it seriously: Persistent indoor elevations alongside symptoms. Can act as an opportunistic pathogen in immunocompromised occupants.

Species 7

Chaetomium

Indicator species for chronic water damage. Often shows up alongside Stachybotrys in long-standing leaks.

Where it lives: Wet drywall, wet wood, water-damaged ceiling tiles. Specifically associated with sustained moisture.
Indoor vs outdoor: Should be near zero indoors. Any consistent indoor presence is a flag.
When to take it seriously: Detection in indoor samples is treated as evidence of long-term water damage. Triggers moisture mapping and source identification before any cosmetic repair.

Watch the Full Walkthrough

Jefferson Prada explains each species and what to do if you find them in your report. Under 7 minutes.

Frequently Asked Questions

What are the most common molds found in Florida homes?+

Florida air sample reports almost always include the same seven species or species groups: Aspergillus/Penicillium, Cladosporium, Alternaria, Basidiospores/Ascospores, Stachybotrys, Curvularia, and Chaetomium. The first four are commonly present in low levels in normal indoor air. Stachybotrys and Chaetomium are not, and their presence in an indoor sample typically signals chronic water damage.

Is Stachybotrys really toxic black mold?+

Stachybotrys chartarum is one of several species commonly called black mold. It produces mycotoxins under certain growth conditions and is associated with chronic water damage. However, color alone does not identify a species, and many dark stains are not Stachybotrys. Only lab analysis with species identification can confirm presence and quantify spore counts.

When should I worry about Aspergillus or Penicillium levels in my home?+

Low levels of Aspergillus/Penicillium in indoor air are normal. The number that matters is the ratio between the indoor sample and the outdoor control sample taken at the same visit. When indoor counts run several times higher than outdoor, it usually points to a hidden moisture source feeding growth indoors, even if no visible mold is present.

What is a normal indoor mold count in Florida?+

There is no fixed numeric standard for normal indoor mold counts. AIHA, IICRC, and the EPA all rely on comparison logic: the indoor sample should track at or below the outdoor control sample for the same species, with species composition that matches the outdoor profile. Reports that ignore the outdoor baseline are incomplete.

Can a mold inspection identify which of the 7 molds are in my home?+

Yes, when the inspector uses an AIHA-accredited laboratory and collects properly controlled air samples (one or more indoor zones plus an outdoor reference). Species identification, spore counts per cubic meter, and chain of custody are standard deliverables of a licensed mold assessment in Florida.

Does Mold Rid Of test for all 7 species?+

Every air sample we collect is analyzed by an AIHA-accredited laboratory that identifies and counts every fungal genus present in the sample, not only the seven discussed here. The full lab report is attached to the assessment so homeowners and insurance adjusters can see the complete picture.

Independent Florida Mold Assessment

Have a Florida Lab Report You Want Reviewed?

Mold Rid Of is a testing-only company (MRSA #3958). We do not perform remediation. Bring us your existing report, or schedule a new air sampling visit, and you get the actual interpretation of those seven species in the context of your home.

Licensed MRSA #3958 . AIHA-accredited labs . Serving Miami, Fort Lauderdale, West Palm Beach, Tampa, Orlando, Naples, Lakeland, Kissimmee, Winter Garden, and Lake Nona.