Mold Surface Sampling

Mold is a byproduct of the breakdown of organic matter, such as plants, wood, and even food and certain beverages. The problem posed to humans by mold is their spores, which can be released into the air and land on damp surfaces indoors, where they will continue to grow, if the conditions are right. Mold growth left unaddressed can quickly spread and result in damage to the structure of a home. More importantly, mold can compromise the respiratory health of susceptible individuals. Although testing for mold falls outside InterNACHI’s Residential Standards of Practice, home inspectors can benefit from getting trained in mold testing and offering this valuable – and sometimes life-changing – service to their clients.

Mold Inspections and Home Maintenance

A mold inspection starts as a home inspection, which is a non-invasive, visual examination of the home’s interior and exterior, and its various systems and components.  

The scope of a mold inspection requires particular knowledge of HVAC systems, roofs, the exterior, and plumbing systems. Musty odors, moisture intrusion via a roof or plumbing leak, or even evidence of suspected mold can warrant a mold inspection. 

Once mold gets a foothold, it cannot always be completely eradicated, so the best cure is prevention. Homeowners must be vigilant about checking for leaks both inside and outside, and making sure their home is free of conducive conditions – the main culprit being water. For instance, firewood stacked up against the side of the house can retain moisture from dew, rain and snow. Leaks should be fixed as soon as possible. And indoor humidity and moisture should be controlled by making sure appliances, such as the clothes dryer and dishwasher, are vented properly, and that the vents themselves are operating as they should. Windows are another place prone to mold growth if the frames are old and damaged, or the seals on the panes have failed. And basements and crawlspaces are notorious breeding grounds for mold, especially if they’re used only for storage, the windows are old or damaged, and/or the area experiences occasional flooding. All of these things fall under the category of home maintenance, which InterNACHI® Certified Professional Inspectors® can educate their clients about.

Testing

Mold testing involves two main methods: air sampling and surface sampling. Both types require analysis by a certified laboratory. In some cases, the local health department can test the mold samples. But it’s more common for a private lab to perform the analysis and generate the results in a report, and the cost is usually included in the price of the test kit.

Along with the sampling equipment, the tools commonly used by home inspectors for a mold inspection of the home’s interior include the following:

  • moisture meter: This basic tool is used to detect moisture in structural components. There are invasive and non-invasive models available.
  • humidity gauge: This measures the humidity level inside a room or building.
  • thermal imaging or infrared (IR) camera: Where visual inspection is not possible, especially for suspected water intrusion that’s inside structural components, damp and wet areas can be detected non-invasively with thermal imaging. Problem areas will show up as dark gradients.

Surface Sampling

Surface sampling is the more common and easiest method for testing for indoor mold.

Here are some methods of surface sampling that can be performed:

  • tape sample: This is the most common method of sampling visible mold, as it allows the inspector to collect several samples in different parts of the home quickly. Sampling kits are typically sold by the laboratories that test for mold and send back the results of their analysis.
  • swab sample: A cellulose swab with a liquid preservative is used to collect any suspected mold for laboratory testing.
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