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Issue 6 Volume 4

June 2006

Mold Sampling and Data Interpretation
by Derrence Freeman
     There are several things people should know about mold. The potential health effects and symptoms associated with mold exposures are allergic reactions, asthma, infections, respiratory problems, and numerous other health effects have been either noted or claimed. Although there is no practical way to eliminate mold and mold spores, controlling the moisture in the indoor environment controls fungal growth. Proper clean up and the elimination of bulk moisture and very high relative humidity solves most mold problems in homes or schools. Correcting the source of the water problem or leak will prevent fungal growth. Maintaining the indoor relative humidity between 30% and 60% will decrease the chance of mold growth. You can control indoor humidity by venting bathrooms, dryers, and other moisture-generating sources to the outside, using air conditioners and de-humidifiers, increasing or adding ventilation and using exhaust fans during cooking, dishwashing, and cleaning. Clean and dry any wet building materials and furnishings within 24 to 48 hours to prevent mold growth. Clean all affected hard surfaces with water and detergent, and dry completely. Adding insulation to windows, piping, exterior walls, roof, and floors will reduce the potential for condensation on cold surfaces. Do not install carpet by drinking fountains, classroom sinks, and floors with leaks or condensation problems. Molds can grow on almost any surface in the presence of moisture, oxygen, and a food supply.

   Molds are visible filamentous fungal colonies that are well-marked mycelium and spore masses. Most fungi produce microbial volatile organic compounds (VOC’s) from which the musty odor commonly associated with fungi comes. Many different fungi produce toxins. All fungi are not molds but all molds are fungi. Fungi are a diverse group defined by filamentous heterotrophic lifestyle, which means they obtain nourishment by digesting plant or animal matter through secreted enzymes that break down organic matter. Spores develop in mushrooms, plant rusts, smuts, molds, and yeasts, etc. It is believed there may be as many as 1.5 million species but only about 75,000 have been categorized. Alternaria alternata, Aspergillus flavus, A. parasiticus, Aspergillus fumigatus, Cladosporium sp., Fusarium moniliforme, and Stachybotrys chartarum (atra) are just a few forms of identified molds.

     When sampling for biological growth, one must first develop a hypothesis and then try to prove it wrong. There are several primary sampling methods: air sampling - (culturable and non-culturable), surface sampling - culturable or direct microscopic examination, dust sampling, contact plates, and content sampling. Air sampling is used to compare the inside spore numbers in cubic meters to the outside and can sometimes give false positives or negatives. This is because typical sample times are very short and may or may not reflect the true number of spores in an environment. A consultant may take more than one outside sample and several inside samples. The inside sample should have lower quantities, the same fungal species, and the same basic distribution. Look for indicator fungal types and an order of magnitude difference. Consider the air exchange rates for the house of the indoor air with the outdoor, activity levels of the inside and outside, the weather, and the magnitude of the fungi present. Samples can be read at different magnifications. The air samples are taken at specific volumes, and are almost always inspected by microscopy at 1000x. This procedure allows for counting and identifying the spores and other debris such as oil, fibers, insect parts and pollen on the slide.

     One of the pros of culturable air sampling is that it allows the viability needed in certain situations. For instance, it differentiates Aspergillus and Penicillium and permits further speciation when required. The cons are that culturable sampling misses fungi that are not viable, it does not compete well in the growth process, it does not germinate on the media provided, and it cannot be analyzed immediately.

     The non-culturable air sampling positive points are that this type of sampling captures all the spores in the air whether nonviable or viable, that do not culture well, that do not compete well, and can be analyzed almost immediately. The negative side is they cannot assess viability, they cannot differentiate between some spore types, and the background debris may limit visibility.

     Non-culturable surface sampling’s primary purpose is to determine whether mold is or has been growing on the suspect surface and what species are growing. The pros of surface sampling techniques are that they reveal what is present, they can be analyzed immediately, and they can differentiate between mold growth and normal fallout. The cons are that they do not provide information on airborne levels, they cannot differentiate between some spore types, they cannot assess viability, and some species may be missed because of high background debris.

     Culturable surface sampling assesses viability, can differentiate between Aspergillus, Penicillium and other species, and allows for further speciation. It does not give information about airborne spore levels. It misses fungi that are not viable, do not compete well, and do not germinate on the media provided. The results may not reflect what is growing on the surface and the results cannot be analyzed immediately.

     Data interpretation will not include any reference to health effects. A medical doctor or other medical professional must handle that aspect of the situation. The consultant’s job is to interpret the data: is there fungal growth in the building? Are people being exposed to it? Are there are any defects in the building needing correction to stop moisture intrusion? Stick to your original hypothesis. For more information on mold, allergens, sampling, and data interpretation visit www.emlab.com.        

Announcements:
Home Energy Rater Training July 10 - 14, 2006.
Take the first step in becoming certified by RESNET as a professional Home Energy Rater.
Register now for the comprehensive workshop to provide you all the information necessary for becoming a professional home energy rater. Training fee includes RESNET exam fee. 

Training will take place Monday - Friday, Sept. 19 - 23, 2005 in Rogers, Arkansas. Registration includes lunches, refreshments and snacks during training, complete Rater Manual and RESNET exam fee.

In this workshop you will:

• Learn about the house as a system
• Learn to produce energy ratings
• Learn to recognize construction flaws
• Learn to sell “energy upgrades”
• Learn to use state-of-the-art diagnostic tools
• Gain knowledge of infrared thermography
• Learn to use REM/Rate software
• Learn how to produce a code compliance report
• Learn to size HVAC systems
• Gain a firm grasp of building science principles and residential energy use

For more information, please contact us at GWS (405)-946-0206 or email info@gwssi.com