Troy, Mi
In Troy, Michigan, "Dale" worked for a water restoration company and needed to test some tile for asbestos. However, some options on our chain of custody were a bit confusing for him. See, on our asbestos testing form for our more commercial clients, we have a checkbox for point counts and for our standard PLM/CVE analysis. This has caused some confusion in the past, so we figured it was a good idea to explain the difference between the two.
Once the asbestos is identified, it must be quantified. There are two major methods of quantification allowed by the method — CVE and point count. CVE stands for Calibrated Visual Estimate, and as it sounds is basically a guesstimate by the analyst as calibrated by previous experience, proficiency samples, and interlaboratory and interlaboratory reanalysis samples. The analyst simply estimates what percentage of the total material present by weight is asbestos. Again, analyst experience is of obvious utmost importance here since it is a determination made solely from experience. As questionable as this methodology sounds, it has worked consistently and correctly over the years without any major modification, and is trusted globally with very little modification. This made Dale feel a bit better about the asbestos testing he wanted done for a client in Troy, Michigan; this was the method he needed for that particular project.
The other major quantification method is the point count. This method uses a microscope insert that has points printed or embossed on it. These points are superimposed over the microscope view area, and then a certain number of these non-empty points (generally 400 or 1000) are randomly selected and identified as asbestos or non asbestos. This is then used to calculate a percentage of a material that is asbestos. For example, if the analyst tallied 3 points of asbestos and 397 point of non-asbestos, that sample would be (3/3+397) = (3/400)=0.75% asbestos. This procedure is significantly more costly and time consuming, and is therefore generally only performed on samples that appear to be very close to the 1% dividing line between EPA regulated asbestos and materials the EPA considers to be non asbestos containing. Materials that contain no identifiable asbestos, and those that contain over 10% are generally quantified by CVE only since the increased precision of point counting is not considered necessary.
An important consideration during all points of our analytical procedure is safety. Since asbestos is known to cause so many potential health issues, it is vitally important that we do everything possible to keep ourselves safe. The biggest safety feature in the laboratory is the fume hood. Every analyst has their own negative pressure fume hood that is calibrated every day of use to ensure that between 75 and 120 linear feet per minute of airflow is being removed from the hood and exhausted through a HEPA filter. The HEPA filter removes at least 99.97% or particles 0.3um or larger from the air, which ensures that all asbestos in the size range that can cause health issues is removed from the discharged air. Beyond this, all analysts wear gloves to protect their hands from exposure to both the asbestos containing materials as well as the various reagents used for preparations.
That is a very quick summary of the mandated method we use in order to produce results that are correct and reliable for your bulk asbestos samples! Hopefully, this clarified things for Dale's asbestos testing in Troy, Michigan. If you would like to know more, both of the above-mentioned methods ( EPA-600/M4-82-020 and EPA/600/R-93/116) are widely available online for no charge since they are official congressional acts and not proprietary information. Same goes for the AHERA and NESHAP acts listed above, although those focus more on the surveying, maintenance, and removal of asbestos containing materials. And of course, if you have any questions, we're always happy to talk shop.