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This document provides information about laboratory identification of fiberglass hazards in air or in settled dust samples collected in residential and light-commercial buildings.

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Laboratory Identification of Fiberglass Fibers

Fiberglass fragments in air, dust, or material samples are easily identified in the forensic laboratory using light and polarized light microscopy and common slide preparation techniques. While glass fibers can be identified using Cargill(R) certified refractive index liquids, it is easier and faster to examine fibers prepared in almost any common slide mounting solution by looking for the following features:

• Smooth sided manmade fibers which may appear in a wide variety of diameters and lengths, but with a characteristic concoidal fracture on the fiber end is key in laboratory identification of fiberglass fragments in air samples or settled dust samples from buildings where screening for fiberglass dust is required
• Presence of colored resin binder on fiber lengths or where fibers cross is another identifying characteristic of fiberglass insulation
• The disappearance of these fiberglass fibers from view in a light microscope when viewed with crossed polars also is used to confirm that glass fibers are present
• Presence of concoidal fractures on the ends of fibers is evidence of glass or fiberglass

The two lab photographs of fiberglass insulation just above show, from left, the characteristic concoidal fracture at the end of a fiberglass fiber, and resinous material used as a binder in fiberglass insulation. The resin binder in fiberglass insulation can appear in various colors and which gives fiberglass its individual characteristic color.

Determining the source of fiberglass particles found in a building: It may be possible to identify the manufacturer of or at least the source of fiberglass fibers found in a building by comparing the color of resin identified in the microscope with colors observed by visual inspection of fiberglass installed in different building areas.

Identifying fiberglass resins and mineral wool insulation: The left hand lab photo of fiberglass show below provides two examples of resinous binder in fiberglass insulation at a lower magnification of about 300x, with the left, triangular resin particle having been bound to two intersecting glass fibers.

Notice the considerable variation in fiberglass fiber diameter in this photo - the fibers in this photo might be from different sources as not only are they characteristically different by metrics, but their resins are of different color.

Problems in identifying very small fiberglass fragments in air and dust samples: Our own field investigations find that fiberglass particles are quite common in indoor air. Unless the forensic particle laboratory is making a point of counting small fiberglass fragments in indoor air or dust samples, only a large-particle count may be provided and the presence and potential effects of fiberglass dust may be underestimated. Furthermore, proper lab procedure and use of mountants with an appropriate refractive index to see glass fragments is critical as otherwise such particles may simply be invisible when viewed using conventional slide preparation methods.

Mineral wool insulation: The right hand photo shown below shows displays a resin binder and thin, varying-diameter fibers of glass mineral wool insulation.

Under polarized light using crossed polars, the glass fibers in these photos will simply disappear from view. (photo not shown - yet)

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FIBERGLASS HAZARDS
  Recognizing Fiberglass Insulation
  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

• 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

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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More Information on Building Diagnostic Inspections and Repairs

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

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

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