Can you see airborne mold spores?

NO. Most mold spores are between 3 and 10 microns in diameter. To give you some perspective, a strand of hair is approximately 100 microns thick. An average mold spore is about 7 microns in diameter, or about the same size as a human red blood cell.  As small and light as they are, mold spores are easily aerosolized, and a spore can stay airborne for as long as 8 hours in a home with no air movement.