MOLD SAMPLING METHODS

1. SURFACE - TAPE LIFT: Nonviable

This method involves applying a clear tape directly to the surface of suspected mold growth. As the tape is removed, a representative sample adheres to the tape. The sample is then analyzed in the laboratory by direct microscopy.

Advantages:

• Quick, easy sampling method.
• Allows for rapid test results.

Disadvantages:

• Can not differentiate between viable and non-viable spores.
• Provides only information on surface mold, not airborne spores.
• Identification of spores to genus level is more difficult.

Sampling method:

1. Apply 1 to 2 inches of clear tape to suspected mold surface.
2. Remove tape slowly. Make sure that a good sample has adhered to the tape.
3. Press the sticky side of tape directly onto a clean microscope slide.
   Alternately: If a microscope slide is not available, tape can be pressed flat onto the inside of any clean plastic bag (use heavy plastic bag). Make sure that the tape is not crumpled, creased, or placed with moist materials.

2. SURFACE - SWAB: Viable and Nonviable

This method involves using a swab to collect a sample from a non-porous surface. The sample is collected from a defined surface area to provide quantification. The swab is washed in a sterile solution and that solution is then cultured. This method is more favorable for bacteria than fungi.

Advantages:

• Quick, easy sampling method.
• Identifies viable molds that are present.
• Allows for ID and quantification (culturable).

Disadvantages:

• Not effective on porous surfaces.
• Quantification can be significantly affected by sampling technique.

Sampling method:

Gently streak a sterile swab over the area of suspected mold growth. The swab may be dry or wetted with a peptone solution.

Note: For quantification, the sample should be collected from a defined surface area (i.e. in²).

3. BULK SAMPLES: Viable and Nonviable

This method involves cutting or scraping a portion of suspected contaminated material. Samples can be analyzed by direct microscopy or cultured.

Advantages:

• Quick, easy sampling method.
• Allows for ID and quantification (culturable).

Disadvantages:

• Destructive sampling technique.

Sampling method:

1. The sample should be cut, scraped, or otherwise aseptically removed from the suspected source of mold growth.
2. Collect a portion small enough for easy transport, while adequately representing the surface being sampled.
3. Place the sample in a clean, new or sterilized container (a new plastic bag may be used).

4. DUST SAMPLES: Viable and Nonviable

This method involves the collection of dust from a porous surface, such as carpeting or fabric. The sample is collected with a polycarbonate filter (0.8 µm pore size) in a cassette using a high volume vacuum pump or a HEPA filtered vacuum cleaner with an interceptor bag. Samples can be analyzed by direct microscopy, cultured, or allergen detection performed by biochemical assay.

Advantages:

• Allows for ID and quantification (culturable).
• Serial dilution can be performed to handle high concentrations.

Disadvantages:

• Some specialized equipment required.
• Low sample weights may give biased results.

Sampling method:

1. Dust samples should be collected into Mixed Cellulose Ester (MCE) or polycarbonate cassettes with 0.8 µm pore size using a high volume vacuum pump.
2. The sample should be collected from a defined sampling area (ie. 1 ft²).
   Note: A minimum of 0.1 grams of dust should be submitted.

5. AIR SAMPLES: Nonviable

The spore trap is a sampling device designed for capturing airborne particles, including spores. The cassette draws air through a slit thereby impacting particles onto a glass slide that is coated so that the particles will stick to the slide. The device is connected to a vacuum pump calibrated at manufacturers recommended flow rates. Spores are identified and counted to provide quantitation of airborne spores.

Advantages:

• Quick, easy sampling method.
• Allows for ID and quantification.
• May indicate mold growth present that is not visible.

Disadvantages:

• Spores can be difficult to identify to genus.
• Aspergillus / Penicillium are reported together.
• Unable to distinguish between viable and non-viable spores.
• Samples from dusty areas may be overloaded with particles.
• High concentrations of spores may be difficult to count; therefore, are estimated.

Sampling method:

Refer to manufacturer's recommendations.

6. CULTURABLE AIR SAMPLES: (Andersen N-6 Sampler):

This method involves drawing an air sample over a petri dish containing culture media. The air is drawn through a sieve plate onto the culture plate. The cultures are incubated and can be identified and enumerated. Different media may be used to culture fungi or bacteria.

Advantages:

• Allows for ID and quantification.
• ID to species level may be possible.

Disadvantages:

• Non-viable spores are not identified, yet they may still be allergenic.
• Some organisms may not produce spores; therefore, are not identified.
• Some viable spores may be desiccated during sampling; therefore, results may be significantly lower than the actual level in the air.

Sampling method:

Refer to manufacturer's recommendations.