Mold Screening

Although there are no defined standards or exposure limits, it is possible to identify houses with mold contamination by comparing the indoor and outdoor levels of mold spores using the air sampling method. A review of the recommendations by the nation's leading testing laboratories shows air sampling to be the method of choice for residential mold screening. 

When properties are found to have higher levels of mold indoors than outdoors, further investigation is recommended. It is assumed that a higher ratio of indoor mold is indicative of an internal mold growth, which, if confirmed, should be corrected. It is generally believed by the scientific community that elevated levels of mold would inevitably lead to the discovery of some form of moisture penetration such as a leaky roof, hidden plumbing leak or other water infiltration problem. 

The following are two common methods of screening for mold: air sampling and sterile swab sampling.

Air Sampling

Screening by air sampling (one of the most reliable, quick and cost-efficient mold tests available today) is recommended if, during an inspection or otherwise, conducive conditions or evidence of mold are discovered. This sampling method requires that at least two samples be taken, one outside and one inside the property. Air samples should be taken inside in any of the rooms where indications of mold are discovered. Only one sample is taken outdoors, called the reference sample, and it is used for comparison to all the other samples taken inside. Indoor/Outdoor mold ratios are often the primary evidence suggesting the likely presence of mold growth within the property.

The air samples are sent to a laboratory specializing in mold analysis.

Note: Air sampling should be avoided if it is raining or recently rained, if it is windy (30 mph or more), or there is a heavy amount of dust in the air (e.g. nearby construction).

Sterile Swab Sampling

Screening by sterile swab sampling can be performed when there are visible signs of mold growth. An individually packaged, sterile swab is used to wipe and collect a sample from the surface of the mold. A separate swab is used for each kind of mold found in the property. 

The sample is then forwarded to the laboratory for analysis.