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Asbestos test lab procedures, photographs, sample preparation, microscopy methods & example lab report: this article provides photos and procedural suggestions used in the forensic laboratory to identify asbestos materials (or probable-asbestos) in flooring and floor tiles.
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Asbestos Test Procedures: Microscopy to Identify Asphalt-Asbestos or Vinyl-Asbestos Floor Tiles in the Laboratory
In this article series we provide photographs and descriptive text of asbestos insulation and other asbestos-containing products to permit identification of definite, probable, or possible asbestos materials in buildings.
[Click to enlarge any image]
While an expert lab test using polarized light microscopy is necessary to reliably identify the presence and specific type of asbestos fiber, or to identify the presence of asbestos in air or dust samples, many asbestos-containing building products not only are obvious and easy to recognize, but since there were not other look-alike products that were not asbestos, a visual identification of this material can be virtually a certainty in many cases.
On occasion, the original flooring packaging or installation literature may be available for a given home: often an extra box of floor tiles was kept for future repairs.
The vinyl-asbestos floor tile package label information, combined with a simple comparison of tiles in the package with tiles installed in the building may be sound confirmation of asbestos-containing materials.
See Vinyl Asbestos Floor Tile Packaging. Historical information about the dates of flooring installation may also be sufficient to rule in or out the possibility that flooring in a building contains asbestos.
Walter McCrone developed and amply documented the forensic microscopy procedures used to identify asbestos in products, air or dust samples.
Certainly asbestos-certified labs who process large volumes of asbestos samples have developed efficient, high-speed procedures to keep the sample analysis costs down, and surely some of those experts have other tips and ideas for effective processing of floor tile samples besides what we will document here.
However on occasion we need to work with less sample material, or very small asbestos floor tile sample fragments in our laboratory. Here we document and illustrate some suggestions for working with small fragments of vinyl-asbestos floor tiles to obtain material for microscopic examination in the laboratory.
Preparing a Small Floor Tile Fragment for Microscopic Examination for Asbestos
In the lab, following Walter McCrone's procedure for teasing out asbestos particles from solid materials such as this floor tile, we broke a small corner off for further examination by microscope.
Tiles are broken, not cut, in order to expose asbestos fibers for removal, slide preparation, and microscopic examination using transmitted, reflected, and primarily polarized-light central stop diffusion microscopy.
This stereo-microscopic view of the edge of this asbestos-floor tile shows the combination of binder and other silicate materials.
Details about Montgomery Ward vinyl asbestos tile flooring are
Below (left) is a microphotograph of materials (probably limestone filler) scraped from the broken edge of the Wards vinyl asbestos floor tile shown above. And below (right) is a 1200x magnification photo taken in our laboratory, showing asbestos fibers teased out of the broken edge of a separate sample of floor tile tentatively identified as 2mm x 9"x9" Armstrong Excelon vinyl asbestos flooring ca 1954-1980).
Because many fibers such as fiberglass and asbestos can be almost impossible to detect microscopically, especially in small fragments, unless they are mounted in a proper medium, Cargille certified refractive index liquids (e.g. n=1.550 or n=1.680) are used to mount asbestos-suspect fibers for microscopic examination.
Although McCrone instructs the technician to "tease out" fibers from the edge of a broken floor tile fragment, the "teasing out process" can be tricky if like the author (DF) you have stubby fingers and the sample is about 1cm square.
We use a very small quantity of fast-setting glue to bond our floor tile fragment to a clean microscope slide.
To the right of the floor tile fragment you'll see a drop of clean mounting fluid. We're using Cargille™ N=1.680 in this example. We'll use the droplet to secure fibres we remove from the sample.
Watch out: don't make the droplet too big or you'll waste time looking for your sample fibers under the microscope; don't place the droplet too close to the glued sample or you may overload it with granular debris during fiber removal; don't place the droplet too far away from the sample or you may lose a fiber during transfer from the sample to the drop.
At above left we show our probe under the stereo microscope, as we gently pick away material from the exposed edge of the glued floor tile sample fragment in order to expose a cluster of fibers for further examination.
Our photo at above right shows that we check our mounting fluid droplet for obvious extraneous debris before using it. If the droplet becomes debris-loaded, it's easy to clean the slide and start with a new drop since we've glued down our sample.
At below left a fiber cluster has been removed from the sample and carried to the nearby droplet of mounting fluid. We did not try to remove all of the debris from our fiber cluster as we wanted to keep the fiber bundle intact. At below right, we still haven't lost the sample as we further prepare the slide with a cover slip. If we are using the same slide and glued-sample to prepare a sequence of fiber trials at different Cargille liquid values, we note the refractive index on the slide so as to keep our lab data accurate.
The following six asbestos microscope photos, below show the asbestos fiber cluster from our vinyl asbestos floor tile under magnification and at different lighting conditions.
Our last photo (above right) show mineral fragments from the sample, possibly limestone.
Watch out: very find powdered asbestos was used as a non-fibrous filler in many products.
Continue reading at ASBESTOS FLOORING HAZARD REDUCTION or select a topic from the More Reading links shown below.
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