Mold testing in College Station

Testing is the part of this trade most open to misuse, so it is worth explaining exactly what each method can and cannot tell you.

The methods

Air sampling with spore traps

A calibrated pump draws a known volume of air across an adhesive slide for a set time. The lab counts and identifies what is captured, and reports spores per cubic metre by genus.

This is the workhorse method. It is the right tool when growth is suspected but not visible, and it is the required method for clearance after remediation.

Its limits: it is a snapshot of a few minutes. Spore release is episodic — disturb a surface and counts spike; leave a room sealed overnight and they settle. A single sample under quiet conditions can miss a real problem, which is why sampling conditions get documented alongside the result.

Surface sampling

A tape lift or a swab taken from visible growth. It answers one question well: is that discoloration actually fungal growth, and what is it. It says nothing about airborne exposure.

Cheap, quick, and the right choice when the question is simply whether the dark patch on the wall is mold or soot or a water stain.

Bulk sampling

A piece of the material itself goes to the lab. Used where the growth is inside a material and a surface sample would not represent it.

Cavity sampling

Air drawn from inside a wall cavity through a small hole. Useful for confirming growth behind an intact finish before deciding to open it, which is a decision worth getting right.

What we do not use

Settle plates — the petri dish left open on a counter — are sold as DIY kits and they are close to useless. Something always grows, because there are always some spores in any indoor air. There is no volume measurement, so no concentration can be calculated, and no comparison to outdoors is possible. A positive result tells you nothing at all, and it is the basis for a great deal of unnecessary alarm.

The outdoor control, and why it decides everything

This is the single most important thing to understand about a lab report.

There is no legal or regulatory threshold in the United States for indoor mold spore concentrations. No number on your report is "over the limit", because no limit exists.

Interpretation is comparative. An outdoor sample taken the same day, in the same weather, is the baseline. Indoor air in a building without a problem should look like outdoor air with lower counts and a similar mix of genera, because indoor spores originate outdoors and get filtered by the building.

Two patterns indicate an indoor source:

• Indoor counts exceeding outdoor counts for the same genus. Air is generally moving from outside to inside, so more inside than outside means something inside is producing it.
• A genus present indoors that is absent or scarce outdoors. This matters more than raw totals. Stachybotrys, Chaetomium and Fusarium require sustained wetting, are poor aerosolisers, and are uncommon in outdoor air here. Finding them indoors in any quantity is meaningful even when the total count looks unremarkable.

A report handed to you without an outdoor control is not interpretable, and you should ask why one was not taken.

Reading the genera

What we typically see in Brazos Valley homes, and what each tends to indicate:

Genus	What it usually means here
Cladosporium	The most common genus in outdoor air locally. Elevated indoors relative to outdoors suggests a source; present at similar levels is normal.
Aspergillus/Penicillium	Reported together because the spores are not distinguishable by this method. Very common indoors. Sustained elevation indicates a damp material somewhere.
Stachybotrys	Requires prolonged saturation, typically of paper-faced drywall. Heavy and sticky, so it aerosolises poorly. Any indoor detection is significant.
Chaetomium	Same story. Strongly associated with water-damaged cellulose materials.
Curvularia, Alternaria	Outdoor genera, common in this climate. Usually reflects outdoor air entering, not an indoor source.
Basidiospores	Mushroom and wood-decay fungi. Elevated indoors can point to decaying wood in a crawl space or wall.

The trap: cause and effect run the wrong way

Worth saying explicitly, because it is how testing gets used to sell work.

A clean air sample does not prove there is no growth. Growth inside a sealed wall cavity may release almost nothing into the room. Conversely, an elevated sample does not by itself prove where the source is or how large it is.

Sampling supports a diagnosis built from visual inspection and moisture readings. It does not replace it. Anyone who tests first, finds a number, and quotes remediation from the number alone has skipped the part that actually matters.

When testing genuinely earns its cost

• Clearance after remediation. Non-negotiable, and it is what the whole job is measured against. See clearance testing.
• Hidden growth. A persistent smell with nothing visible, where cavity sampling can confirm before you open a wall.
• Documentation. Insurance claims, real estate transactions, landlord and tenant disputes. The document is the deliverable.
• Health concerns. Where a household member is symptomatic and a physician wants to know what is in the building.
• Establishing extent. In a large building, sampling across zones helps map how far it has spread.

And when we will tell you to skip it

Visible growth, known water source, obvious extent. Testing confirms what you already know and delays the work by a few days. Put the money into doing the removal properly and into fixing the leak.

The one exception, again: if you need the paperwork for someone else, the paperwork is worth buying.