Toxic mould fungus (Stachybotrys chartarum), coloured scanning electron micrograph (SEM). Fruiting structures with spores. Often known as black mould. Several strains of this fungus (S. atra, S. chartarum and S. alternans) are synonymous. This fungus may produce a trichothecene mycotoxin (Satratoxin H) which is a poisonous by inhalation. The toxins are present on the fungal spores. The toxins produced by this fungus will suppress the immune system affecting the lymphoid tissue and the bone marrow. The spores will die readily after release but the dead spores are still allergenic and toxigenic. Magnification: x800 when shortest axis printed at 25 millimetres.