PEL does not collect mold samples nor conduct investigations. However, we are often asked about both. Here are some responses from agencies, consultants, and colleagues on these subjects. 

“When should a mold inspection or mold testing be considered?”

The Environmental Protection Agency has this to say about the matter:

Is it necessary to sample for mold? If there is visible mold growth, sampling is not necessary. Because no EPA or federal limits have been established for mold or spores, sampling can’t be used to verify compliance of a building with federal mold standards. To determine whether an area has been properly cleaned or remediated, surface sampling can be helpful. Professionals with expertise in mold sampling in Houma should use their experience to design sampling protocols and methods. They also need to interpret the results. The American Industrial Hygiene Association, the American Conference of Governmental Industrial Hygienists and other professional organizations recommend that sample analysis be done using the analytical methods.


  • There are no EPA/other federal limits on mold spores. Therefore, sampling cannot be used to verify compliance of a building with federal mold standards.
  • Sampling can be used for determining if an area has been cleaned sufficiently or properly remediated.
  • Professionals must use proper sampling protocols and methods to accurately interpret the results.
  • You can use the American Conference of Governmental Industrial Hygienists’ (ACGIH) analytical methods to analyze samples.

What are the best types of samples to be collected and when is sampling required?

  • Mold “clearance” sampling is performed when there is a mold problem. This happens after a mold remediation company has treated the area and removed any mold growth.
  • To ensure that a structure is free from mold growth, general mold investigations are performed often before or during real estate transactions.
  • People who have suffered from an allergy or other condition that is related to mold may request professional help.

The professional who is conducting the mold investigation will determine which conditions trigger what type of sampling. If a homeowner simply wants to find out the type of mold in their home, they can submit their own samples.

There are many types of sampling methods:

Indoor Air Sampling – Air samples are the most commonly collected environmental sample field investigators collect in order to study indoor air quality. There are two types of air sampling: viable and non-viable. Viable sampling is the collection of mold spores onto media (typically an impaction plate). The media must contain mold spores alive to allow the testing to take place. While non-viable sampling includes the collection of mold spores onto media (typically an allergenco D cassette or air-o cell cassette). mold analysis determines whether the spores are alive (viable), and dead (nonviable). To ensure that sampling cassettes do not become overloaded and to allow for good air spore dispersion, the sampling duration is usually set. Outdoor environments that are free of visible dust will be sampled for 10 minutes, while indoor environments that have people present and moderate activity will be sampled for 5 minutes. Sample times can be reduced to 1 minute in extremely dusty environments like drywall renovation.

Tape Lift Sampling: For microscopic inspection of suspected stains, settled dust, and spores, tape lift samples are usually collected with clear adhesive tape or an adhesive slide. Tape lifts offer a non-destructive and effective method of sampling. You collect the samples by applying a clear adhesive to the surface of interest and then releasing it using light pressure. The sample is then removed from the surface and placed onto a slide/surface. Finally, it is placed into a bag for submission to the laboratory.

Bulk – This is a destructive testing of materials (i.e. Bulk sampling is a collection of pieces of carpet or building materials that are tested for mold growth. Bulk sampling is a collection of small amounts of material that can be easily transported to the laboratory. A 2″x2″ square piece will suffice. A representative sample of the bulk sample is taken and can be cultured to identify species or analyzed by direct microscopy to identify genus.

Swab – A sterile cotton or synthetic fiber tipped swab can be used to detect suspected mold growth. This method allows for the collection of samples that can be used to identify species or for analysis using direct microscopy. Identified spores will usually be reported as ‘present/absent’.

Carpet (filter type) Cassette : To collect pollen, mold and other particulates, a carpet cassette can be used with a portable pump. This method allows for the collection of samples for species identification and analysis using direct microscopy to identify genus.