Assisting Stack Testers
Through Microscopy: A Case Study
THE PROBLEM: What do you do when the weights collected in a Method 201A/202 catch exceed the allowable limits? Do you need to know what is present on a Method 5 filter or in the back half? Identifying the collected material is a necessary first step in determining what is going on.
THE ANALYSIS: Microscopy methods can be used to identify the collected material. Polarized light microscopy (PLM), scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM/EDS) and micro-Fourier transform infrared spectroscopy (micro-FTIR) are all used to identify the materials caught on filters, in cyclones and impactors and in the back half.
THE IMAGE: The image to the right shows a polarized light micrograph of one of many fibers found in the back half of one sample, and these fibers made up the majority of material present. Further analysis by micro-FTIR confirmed their identity as paper fibers.
THE OUTCOME: MVA’s analyses of this back half sample showed that the main components present were paper fibers not arising from the stack, allowing the client to satisfactorily explain an out-of-compliance finding.