Mold particles from <i>Aspergillus fumigatus, Penicillium chrysogenum, Aspergillus versicolor</i>, and <i>Stachybotrys chartarum</i> have been linked to respiratory‐related diseases. We characterized X‐ray‐inactivated spores and hyphae fragments from these species by number of particles, morphology, and mycotoxin, β‐glucan and protease content/activity. The pro‐inflammatory properties of mold particles ...