There are several methods to analyze concentrations of airborne asbestos fibers. The two most commonly used methods are PCM and TEM. In order to measure asbestos fiber concentrations in air samples, a Phase Contrast Microscopy (PCM) is being performed.
This method is usually used to regularly check asbestos abatement sites and also for environmental monitoring. Further to that PCM is also the state of the art testing method for personnel monitoring and in order to conduct clearance testing for small scale asbestos abatement projects. PCM is a method that is known for delivering test results quickly at rather low costs. But there are always two sides to each story, because undeniably, this technique does have its limitations.
PCM is based on magnifying asbestos fibers by 400X, using a light microscope. The problem with that technique is: only fibers that are bigger than 0.25 microns in diameter will be detected. And further to that, Phase Contrast Microscopy does not differentiate between asbestos fibers and other fibers, such as from fiberglass, cellulose or gypsum. This means that even if PCM reveals high concentrations of fibers, there is still no conclusive indication of asbestos presence. Which consequently means, if the test indicates low counts of fibers, we cannot assume that we are dealing with an asbestos free environment. So in sum, Phase Contrast Microscopy only provides us with a picture of the total fibers within a given range.
Understandably, in many cases we need to conduct more in depth testing and because of the limitations of Phase Contrast Microscopy, many public authorities do insist on a technique called TEM to get more complete and reliable data regarding asbestos presence. TEM, or Transmission Electron Microscopy, in comparison to PCM, is a rather sophisticated asbestos analysis method. It also allows us to actually characterize asbestos minerals. Nowadays, this method is the defined standard procedure on order to conduct asbestos airborne investigations, asbestos abatement clearance testing and a number of environmental monitoring and diagnostic operations. With TEM, magnifications of 20,000X or even more are possible. Further to that, the method also includes the use of chemicals (EDXA) and mineralogical techniques, such as SAEDP. This allows us to clearly differentiate asbestos fibers from fibers of non asbestos materials and furthermore even determine what kind of asbestos is present in the provided sample. As for the asbestos analysis turnaround time: including the preparation and the actual analysis of the sample, the procedure can be completed within six hours.