sharing our knowledge.
Photographic gallery.  Thousands of particles under the microscope.
Black Particles In Homes Under the Microscope

Black Shoe Wear and Charred Wood

This is from an in-home office in Redmond, Washington, hundreds of miles from the nearest wildfire. The shoe wear particle is in the upper left. The charred wood (a hardwood) is near the center. The fungal particle in the lower right would also appear black without reflected darkfield illumination.

Transmitted Crossed Polarized Light and Reflected Darkfield Illumination


Shoe wear particles are common in homes, offices, and classrooms. The "rubber" soles come in a variety of colors but are typically heavily filled with mineral fillers. The tapered cylinder shape is typical. Charred wood, to be identified as such, must be brittle and break with sharp edges. It must also have sufficient morphology to be identifed as exhibiting wood cellular structure.

Significance in the Environment:

Indoor environments not exposed to wildfire often contain black particles in excess of 1% of the total particulate matter. The amount of charred wood alone can exceed 1% in some of these homes, especially if they or their close neighbors use a fireplace or woodstove.

Characteristic Features:

Associated Particles: