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This document provides information about the occurrence of problematic toxic or allergenic mold growth in fiberglass insulation that appears, on visual inspection, to be clean in residential and light-commercial buildings. This 720x photograph shows active fungal growth along the surface of a fiberglass insulation fiber collected the suspended ceiling of a building suffering wet conditions and moldy in-slab HVAC ducts.

Mold is often found in basement fiberglass insulation, crawl space fiberglass insulation, fiberglass wall insulation, heating or cooling duct fiberglass insulation, and attic or roof insulation in buildings which have either been wet or have been exposed to high levels of mold from other sources.

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Moldy building or duct insulation may look clean on visual inspection

The fiberglass insulation falling into a crawl space at the left hand photo above is obviously suspect for having been wet and possibly contaminated by rodents, insects, or toxic or allergenic mold.

But what about the nice new clean looking fiberglass insulation in the right hand photo.That clean-looking fiberglass insulation was located over a clean-looking basement of a home less than ten years old. But a closer inspection of the home, its exterior, and its basement (as well as attic) found several clues suggesting that during one or more prior springs the basement had been quite wet. Check our our Mold-Contaminated building insulation photo just below.

The photo at above left shows clean looking insulation; in fact this is one of our baseline samples of clean fiberglass insulation fragments (taken from a sample of new fiberglass building insulation).

The photo at above right shows dirty looking insulation from an older building. The right photo of a sample collected from fiberglass insulation in an older building exposed to moisture and leaks shows a high level of particulate debris, almost certainly including organic debris such as skin cells, animal hair, and insect fragments which can form a base for mold growth. But we didn't detect problematic mold in either of these cases.

Of course a high level of insect fragments, mite fecals, or rodent fecal and urine-contaminants in any building insulation can result in indoor air quality complaints if air and dust move from that particle reservoir into the living area.

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FIBERGLASS HAZARDS
  FIBERGLASS CONTAMINATION TEST PROCEDURE
  Recognizing Fiberglass Duct Insulation
  Lab Identification of Fiberglass
  Fiberglass Fragment Hazards
  Fiberglass Detection in Building Air
  Mold in Fiberglass Insulation
  Mold in Foam Insulation
  Moldy insulation may look clean
  Why does mold grow in fiberglass?
  When to test insulation for mold
  How to Test for Mold in Insulation
  Fiberglass Hazard References
INSULATION INSPECTION & IMPROVEMENT

For more information about fiberglass as an indoor air quality concern see:

• Fiberglass in Indoor Air, HVAC Ducts, and Building Insulation
• Fiberglass Particle Identification in the Fiberglass Test Laboratory
• Goodman Gray Flex Duct Deterioration and Failures
• Mold in Fiberglass Insulation
• Optimum Indoor Air Filters
• Owens Corning Flex Duct Deterioration and Failures
• World Trade Center Dust Particle Identification

• Fiberglass building insulation and HVAC duct work insulation hazards
• Fiberglass carcinogenicity: Glass Wool Fibers Expert Panel Report, Part B - Recommendation for Listing Status for Glass Wool Fibers and Scientific Justification for the Recommendation", The Report on Carcinogens (RoC) expert panel for glass wool fibers exposures met at the Sheraton Chapel Hill Hotel, Chapel Hill, North Carolina on June 9-10, 2009, to peer review the draft background document on glass wool fibers exposures and make a recommendation for listing status in the 12th Edition of the RoC. The National Institute of Environmental Health Sciences is one of the National Institutes of Health within the U.S. Department of Health and Human Services. The National Toxicology Program is headquartered on the NIEHS campus in Research Triangle Park, NC.
• Fiberglass insulation mold: occurrence of mold contamination in fiberglass insulation can be impossible to see with the naked eye, but can be significant

For more information about asbestos as an indoor air quality concern with focus on easy ways to identify asbestos materials in buildings, see:

• Asbestos Identification in Buildings: How to find & identify asbestos-containing materials
• Asbestos in Good Condition
• Asbestos HVAC Ducts - Asbestos Materials On or In Heating and Cooling Duct Work
• Asbestos paper duct wrap
• Asbestos Transite Chimneys, Flues, & Pipes in Buildings
• Asbestos under the microscope
• Asbestos Vibration Dampers & Asbestos in the Air Handler
• Ceiling tiles: How to recognize ceiling tiles that may contain asbestos
• Examples of unusual uses of asbestos in buildings

• Fiberglass in Indoor Air, HVAC ducts, and Building Insulation, Indoor Air Quality Investigations: (this article)
• Mold in Fiberglass, when, why, and how fiberglass becomes a reservoir of problem mold in buildings.
• Lab Identification of Fiberglass photographs and text assist in laboratory identification of fiberglass fibers and fragments in air, dust, or material samples in the laboratory using forensic microscopic techniques.
• Asbestos: How to find and recognize asbestos in buildings - visual inspection methods, list of common asbestos-containing materials

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• ...

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