Case Studies

An Irritating Situation:
After having work done on a residential HVAC system, the occupants of the house noticed they had an elevated degree of eye, nasal and skin irritation. Dust samples were collected from different rooms in the house and submitted for analysis. When the samples were examined using Polarized Light Microscopy, the samples were found to contain very small fragments of fiberglass insulation. The small fragments were about 8 – 12 micrometers in diameter (1/4 the width of a human hair) and 20 – 750 micrometers in length. Some of the yellow adhesive which binds the fiberglass together can be seen on the fragments. These small friable fragments with sharp irritating ends were causing the undesirable itch and irritation.

Fiberglass fragments found in dust sample – 200X

Clogging Up Progress:
A leach field drain pipe was constantly clogging. Quite often, fluid handling systems dealing with aqueous solutions which experience basic pH upsets will have a problem with the precipitation of calcium carbonate. When this sample was first examined with Polarized Light Microscopy, the optical properties and crystal morphology of the particles obtained from inside the pipe did not match those of calcium carbonate. The sample was then examined using a Scanning Electron Microscope equipped with an Energy Dispersive Spectrometer. The high energy electron beam in the instrument puts the atoms in the sample particles in a higher energy excited state. In order to return to a lower energy state, they emit energy in the form of photons. These photons are high enough in energy that they are in the X-ray region of the electromagnetic spectrum. The wavelengths of these X-rays are specific for each element in the periodic table. The intensity of the signal is also proportional to each atom’s concentration. For this sample, the material clogging the pipe was found to be magnesium phosphate, Mg3(PO4)2.

SEM Image of material clogging pipe
Energy dispersive spectrum of material clogging pipe

What’s Cookin’ in the Kitchen?
A school cafeteria was experiencing a strange growth near their dishwashing area. This off white coating would seem to grow with time. After the sample was examined with the Polarized Light Microscope, the sample was found not to be biological at all. The sample consisted of tiny elongated crystals. They were orthorhombic crystals with high birefringence using crossed polarized light. The optical properties of the crystals indicated they were aragonite, which is a form of calcium carbonate. The hot and steamy conditions near their dishwashing station along with the right water conditions precipitated the calcium carbonate crystals. To verify the results, a Nujol mull of the sample was made and analyzed by FTIR. The FTIR spectrum is matched to a standard spectrum below. The gray areas indicate where known peaks from the sample preparation procedure are located.

Kitchen residue using plane polarized light – 200X

FTIR Spectrum of kitchen residue sample (Nujol mull) and matching calcium carbonate standard
Kitchen residue using crossed polarized light – 200X