Glass Fiber From an HVAC System
In the case of this fiber the resin exhibits a stress
birefringence not associated
with the glass fiber. This is often seen in resin highly filled with clay or
amorphous silica. This type of
filled resin is used in sound board from the ventilation system and in some acoustic
ceiling tiles. The particles
adhearing to this fiber and the frequency of this type of fiber seen in this
environment indicated the HVAC system
as the source.
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.
Characteristic Features:
Associated Particles:
References:
