Didn’t want to hijack the thread in which this post appeared
This site says, "A typical mold will be about 10 microns (0.0002 inches) in size, and they can grow anywhere where there is sufficient warmth, food, and humidity in the air to absorb moisture. … As a matter of fact, the Journal of Property Management reports that one square inch of drywall can contain 1 to 10 million spores as small as 1.5 microns in size! There are more than 1.5 million species in existence, and some molds grow only in the home. "