Photograph of chopped fiberglass insulation Fiberglass Particle Identification in the Fiberglass Test Laboratory

  • LAB IDENTIFICATION OF FIBERGLASS - CONTENTS: Microscopic identification of fiberglass - Lab and field photographs of fiberglass insulation products. Guide to fiberglass fragment identification in the laboratory
  • POST a QUESTION or READ FAQs about lab procedures for the identification of large & small fiberglass fragments in air & dust samples from buildings

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Lab procedures for fiberglass dust testing:

This document provides forensic laboratory procedural details for the 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 & Fragments

Certainteed blown in fiberglass (C) Daniel FriedmanFiberglass 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 Cargille(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:

photo of concoidal end fracture on fiberglass fragment photo of resin binder on fiberglass insulation fragments

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.

photo of resin binder on fiberglass insulation fibers photo of glass wool insulation

Under polarized light using crossed polars, the glass fibers in these photos will simply disappear from view. (photo not shown - phase contrast microscopy or use of special mounting fluids with an appropriate refractive index may be needed especially to identify small fiberglass fragments.)

Photographs of Unbonded Fiberglass Insulation - "Blowing Wools"

Certainteed blown in fiberglass (C) Daniel Friedman Certainteed blown in fiberglass (C) Daniel Friedman

Above (left) we show a macro photograph of white blown-in unbonded InsulSafe® building insulation sold by CertainTeed and provided by a homeowner who asked our lab to study dust samples from her home. At above right is the same insulation shown in the stereo microscope at about 20x, and below the same material is magnified to 720x.

Identifying Contents of House Dust to Screen for Building Insulation

Certainteed blown in fiberglass (C) Daniel Friedman fibers not fiberglass (C) Daniel Friedman

Above (left) we show a 720x micro-photograph of white blown-in unbonded InsulSafe® building insulation sold by CertainTeed. At above right our photo shows the dominant particles in the dust sample from the home under study. Magnified to 720x the fibers we found were primarily cotton, with some linen and a few synthetic fabric fibers. There was virtually none of the insulation fibers provided for comparison (above left) as a possible source of dust in the home.

fibers not fiberglass (C) Daniel Friedman fibers not fiberglass (C) Daniel Friedman

Above (left) a client photo shows a heavy and rapid dust accumulation on building surfaces. At above right our lab photo shows that the prime contents of the dust were fabric fibers and starch granules, not building insulation in this case. - DF & WW 6/2010.


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