The presence of mold usually implies decay, although some molds are used deliberately in, for example cheese-making, and for the production of antibiotics.
The numerous spores released by mold does not cause direct harm in humans, but the hyphae grown from those spores could attach to cells along the respiratory tract and cause problems in those with weak immunity.
Mould in buildings is currently a topic of considerable interest, although the relationship between moulds and human health is not yet well-understood.
Moulds are everywhere and are widely used for beneficial purposes in the food industry, in medicine and in science.
Mould is not common on wood, and the stain is quite likely due to something harmless such as dirt, iron filings, or staining fungi that merely colour the wood without damaging it.
Moulds are simple, microscopic fungi that grow on the surfaces and crevices of objects such as wood, carpeting, and cellulose-based objects including drop-down ceiling panels and drywall.
Mould and people have co-existed for thousands of years, and most individuals have developed a tolerance to mold exposure.
The ability of moulds such as stachybotrys to release mycotoxins is the suspected reason for the most extreme symptoms of mold exposure.