Types of Mold Testing: Part 4 – Wall Cavity Testing

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Not all mold problems grow in plain sight. Some of the most damaging infestations hide inside walls, under floors, or behind cabinets. These hidden areas stay damp long after a leak or flood, creating perfect conditions for mold growth. That’s why inspectors often use inner-wall cavity testing to confirm whether mold is present where you can’t see it.

How Cavity Testing Works

  • A trained inspector drills a small, discreet hole into the wall or ceiling near the suspected area.
  • A sterile tube or cassette is inserted to pull an air sample from inside the cavity.
  • The sample is sent to a certified laboratory, where spore counts are compared to baseline indoor and outdoor levels.

This process gives a direct look at what’s happening behind the surface — without having to tear down entire sections of drywall.

When It’s Used

  • Insurance Claim Disputes: Homeowners are often told “no visible damage, no problem.” Cavity testing can prove hidden mold exists and help validate claims.
  • Follow-Up to Positive Tests: If a surface or air sample in the room already showed elevated spores, cavity testing helps confirm whether mold is also thriving behind the walls.
  • Suspected Leaks: When there’s a history of plumbing issues, roof leaks, or water intrusion but no obvious staining, cavity testing can identify hidden moisture damage.
  • Mystery Odors: A persistent musty smell is often the first clue that mold is active behind finished surfaces.

Why It Matters

Mold hidden inside walls can spread unchecked for months, making remediation more invasive and expensive. By detecting the problem early, inner-wall cavity testing provides homeowners with clear answers — and the documentation they need when dealing with insurance companies, landlords, or contractors.

Protect Your Property with Expert Mold Testing

If you suspect hidden mold in your home or business, don’t wait for the damage to spread. At MSI, we use industry-standard testing methods, including cavity sampling, to uncover mold where it hides and provide you with a clear plan for remediation.

Mold Testing Part 2: Surface Sampling

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What Is Surface Sampling?

While air testing measures spores floating in the air, surface sampling targets visible or suspected mold growth on specific materials. This method involves swabs, tape lifts, or bulk samples taken directly from the surface of walls, furniture, or building materials.

When Is Surface Sampling Needed?

  • Visible Spots or Stains – to confirm whether discoloration is mold or another substance.
  • After Water Damage – to verify whether mold has developed on building materials.
  • Post-Remediation Clearance – ensuring the affected areas are truly mold-free.
  • Hidden Suspicions – when air samples come back inconclusive but the area still looks questionable.

Different Methods of Surface Sampling

  • Swab Samples – cotton-like swabs collect material from suspicious areas.
  • Tape Lifts – adhesive tape lifts spores directly off surfaces for lab analysis.
  • Bulk Samples – actual pieces of contaminated material (like drywall) are sent to the lab for testing.

In some cases—such as disputes between landlords and tenants, insurance claims, or litigation—surface sampling provides a level of certainty that air testing cannot always guarantee. Because spores don’t always become airborne, an air sample might miss contamination that’s clearly visible on a surface. By taking a direct lift from the material itself, you know exactly what is present in that location.

This makes surface samples a powerful tool when clear, documented evidence is needed. Whether it’s a legal case, a landlord–tenant disagreement, or simply providing peace of mind, surface testing can deliver indisputable results that stand up to scrutiny.

Limitations of Surface Sampling

Surface tests don’t measure what’s in the air and can’t determine the overall air quality of the property. They also only represent the spot tested, not the entire room. That’s why professionals often use surface samples in combination with air testing for a complete picture.

Why Professional Sampling Matters

Knowing when to use surface testing—and how to interpret the results—isn’t always straightforward. At MSI, we’ve been conducting mold inspections and testing since 1998, and we know which situations call for air testing, surface testing, or both.

Takeaway

Surface sampling is a valuable tool, but it’s just one part of a complete mold inspection strategy. Trusting a certified professional ensures accurate results and the right plan of action for your property.

What is Cladosporium?

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Cladosporium is the genera most frequently encountered in both outdoor and indoor air. It is found in elevated levels in water-damaged environments. Some species may be resistant to certain types of treated lumber. Cladosporium appears gray to black or very dark green and can have a powdery appearance. The genus Cladosporium includes over 30 species. The most common ones include Cladosporium elatum, Cladosporium herbarum, Cladosporium sphaerospermum, and Cladosporium cladosporioides.

Cladosporium is a dematiaceous (pigmented) mold widely distributed in air and rotten organic material and frequently isolated as a contaminant on foods. Some species are predominant in tropical and subtropical regions . Also, some Cladosporium spp. were isolated from fish and were associated with findings of infection. Cladosporium is a common fungus that is a known and documented aero-allergen which is usually associated with plants, wood products, and leather goods; the spores are easily made airborne and as such are a common cause of respiratory problems; allergic reactions and can be an agent for hypersensitivity diseases; it is as a parasite in infections of the skin, soft tissues or nails and has been documented in cases of Blastomycosis, Candidiasis, Chromoblastomycosis, Histoplasmosis, Entomophthoramycocis, Phaeophphomycocis and Keratomycosis.

The findings suggest that fungal antigens from species found in homes are commonly associated with skin sensitization in an allergy clinic population with upper or lower respiratory allergy. No specific relationships were found, however, between the prevalence of fungal species in the home environment and the prevalence as skin-test allergens.

Most commonly identified outdoor fungus. The outdoor numbers are reduced in the winter. The numbers are often high in the summer. Often found indoors in numbers less than outdoor numbers. Indoor Cladosporium may be different than the species identified outdoors. It is commonly found on the surface of fiberglass duct liner in the interior of supply ducts. A wide variety of plants are food sources for this fungus. It is found on dead plants, woody plants, food, straw, soil, paint and textiles. Produces greater than 10 antigens. Antigens in commercial extracts are of variable quality and may degrade within weeks of preparation.