Chaetomium ascospores are found outdoors and indoors. The spores are brown and lemon-shaped with a germ pore (two in some species). They range in size from 8 -12 µm in length and 5-7 µm in width.
Chaetomium spores from an outdoor air sample
Water damaged indoor building with Chaetomium, Stachybotrys, and Penicillium/Aspergillus-type spores