Glass Fiber from a Wall Perforation

Transmitted Oblique Off Crossed Polarized Light Illumination

Definition/Function:

Significance in the Environment:

Fibers in a moving air stream collect particles from that air stream that are about the same diameter or smaller than the diameter of the fiber. There are a couple of different micro-environments that can expose glass fiber to moving air streams indoors. The most obvious is the heating, ventilation, and cooling system (HVAC system). Another source is glass fiber insulated walls with perforations. All walls have per- forations at electrical outlets, switches, or along the baseboard of the wall. Normal "breathing" of the wall creates the air movement and over time the glass fibers at those perforations will become coated with these small particles. The types of particles on the surface of the fiber can be used to determine if the fiber was exposed to outside air, inside air, filtered air, or recycled air with reasonably high probability using assembalge analysis. In this case the red of the resin suggests blanket insulation but the particle accumulation clearly indicates exposure to a moving air stream. The size of the particles (quite small) indicates diffusion as the dominant deposition mechanism rather than impaction. This appears to be from a wall perforation. The source of glass glass fiber in an environment is never based on a single fiber but rather the total glass fiber population. There are often multiple sources of glass fiber in an environment and the glass fibers are distributed by their attributes into the different populations. The source of the individual populations is then determined based on the characteristics of all the fibers in each population. There are always some fibers that lack sufficient asso- ciations to place them in a population. These fibers are allocated proportionately after the various sources are indentified and their relative contribution to the total is determined.

Characteristic Features:

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