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Carpet Ghosting

Carpet Ghosting – Soil Filtration – Fume Fading – Black Carbon

The outer edge of carpet is black or dark, why?

In recent years, there have been an increasing number of complaints relating to the sudden and unexpected appearance of soot-like material observed in homes and commercial buildings. These stains may form on carpets, walls, plastic objects and other materials, and have been noted around ventilation grilles and electrical outlets. In many cases the culprit for this “ghosting” phenomenon is the formation of Black Carbon.

Black Carbon is a fine-grained solid residue that results from incomplete combustion of hydrocarbons. Common sources of Black Carbon that can cause residential or commercial property damage include candles, fuels such as oil, propane and natural gas used in gas appliances and gas log fireplaces, firewood burned in a fireplace or a wood-burning stove. Even printer cartridges can produce a manufactured Carbon Black that is nearly identical to Black Carbon (Soot).

Black Carbon particles may appear as individual spherical particles or as grape-like conglomerates. The diameter of the individual particles generally varies between 10nm to 70nm. Considering the size and the specific morphology of Black Carbon particulate, the analysis for identification of Black Carbon is best performed by electron microscopy ensuring the appropriate magnification range for imaging. Transmission Electron Microscopy can easily achieve a magnification of 100,000x, which is more than sufficient to observe individual particles. Even the best light microscopes can only achieve 1,000x magnification. At a magnification of 1000x observations are limited to particles no smaller than 300nm. This is roughly the size of the smallest bacteria. Black Carbon particles are generally one order of magnitude smaller.

However, the majority of nano-size particles, such as iron oxides, titanium dioxide or aluminum oxide have the same morphology. For example, titanium dioxide (TiO2) is a common interference due to its spherical morphology and its expansive use in food, commercial and pharmaceutical products. Therefore, the particles elemental composition should also be determined by energy dispersive x-ray analysis to verify if the material sampled is actually Black Carbon.

The identification of Black Carbon is performed using Transmission Electron Microscopy (TEM) in conjunction with Energy Dispersive X-Ray Analysis (EDX). Sample collection for airborne Black Carbon should be performed according to the NIOSH 5000 method. Dust “wipe” sampling can be performed with 1 square inch alcohol wipes such as those used to cleanse your arm before a shot with a hypodermic needle.

Identifying the origin of combustion product formation can help to eliminate potential sources. The identification of the source of Black Carbon is performed using Transmission Electron Microscopy (TEM) in conjunction with Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Gas Chromatography / Mass Spectrometry (GC/MS). The analysis is based upon the different particle sizes and the presence of selected functional groups in the samples that distinguish sources such as paraffin residue from candles or fuel oil from oil heaters.