1. Air Testing (Air Quality Sampling)
Air testing measures the concentration of invisible mold spores floating in your living space. It is critical for finding hidden mold behind walls or under floors. To get an accurate reading, an inspector must take a “control sample” outdoors to compare with the indoor levels. [1, 2, 3, 4, 5]
- Spore Trap / Non-Viable Sampling: An air pump draws a specific volume of air through an industry-standard cassette—such as the Air-O-Cell Cassette—forcing spores onto a sticky slide. A lab technician views the slide under a microscope to count the spores. It detects both alive and dead spores quickly but cannot determine if the mold is still actively growing.
- Culturable / Viable Air Sampling: Air is pulled onto a petri dish containing a nutrient agar growth medium. The lab waits several days to see what grows. This method allows scientists to pinpoint the exact species of mold, but it takes much longer (7 to 14 days) and misses dead spores that can still cause allergic reactions. [1, 2, 3, 4, 5]
2. Surface Testing
Surface testing determines whether a specific visible substance or stain is actually mold, and what type it is. [1, 2]
- Tape Lift Sampling: The inspector presses a specialized piece of clear adhesive tape onto the suspect area and lifts it off. The tape is placed on a glass slide and analyzed under a microscope. This is the preferred method for flat, smooth surfaces.
- Swab Sampling: A sterile, cotton-like swab is rubbed over a localized area (usually an uneven or porous surface) and sealed in a tube containing a preservative gel. [1, 2, 3]
3. Bulk Testing
Bulk sampling involves physically cutting out and removing a piece of an affected structural material. An inspector will take a small chunk of contaminated drywall, wood, carpeting, or insulation and seal it in a bag for laboratory analysis. This is highly effective for discovering if mold has completely penetrated deep into a porous building material. [1, 2, 3, 4, 5]
4. Advanced DNA-Based Testing
- ERMI (Environmental Relative Moldiness Index): This is a highly accurate method where you collect dust from across the home using a specialized vacuum attachment or microfiber cloth. The laboratory utilizes MSQPCR (Mold Specific Quantitative Polymerase Chain Reaction) to map out unique DNA sequences from 36 specific mold species. While expensive, it provides a comprehensive history of the home’s fungal ecology. [1, 2]
Comparison of Core Testing Methods
| Testing Type [1, 2, 3, 4, 5, 6, 7, 8, 9] | Best Used For | Pros | Cons |
|---|---|---|---|
| Air Testing | Finding hidden mold or tracking overall air quality. | Detects invisible spores; tells you what you are breathing. | Only represents a snapshot in time; spore counts fluctuate. |
| Surface Testing | Confirming if a visible stain is active mold. | Inexpensive; establishes exact genus at the spot. | Only tests a tiny, localized area; can’t detect hidden airborne spores. |
| Bulk Testing | Assessing deep damage in building materials. | Shows if mold is growing inside a wall or material. | Destructive; requires cutting a physical piece out of the home. |
If you are suspecting a problem in a home, are you dealing with a visible stain/discoloration, or is there an unexplained musty odor with no visible source?