News stories about these problems have grabbed recent headlines. Incomplete combustion of gas fired appliances can occur from incorrectly installed flue pipe assemblies, dirty or incorrectly balanced gas traines or inadequate make-up air. Soot may also escape from cracked fireboxes in fireplaces, a poorly designed flue pipe, or rusted or cracked heat exchanger assembly. All these problems can allow soot to be deposited in the walls, attic areas, and into the living areas of modern homes. The problem in the limelight recently is mold and fungus, including the Stachybotrys atra, and Stachybotrys chartarum fungus which can produce mycotoxins.
Mycotoxins are secondary chemical metabolites of the fungi and are usually contained in the spores.
Toxicity can arise from exposure to the mycotoxins containing spores in the air or through skin contact with the toxigenic fungus. The sick building syndrome can arise from toxigenic or eleagenic fungi or certain species of penicillium, some aspergillus, stachybotrys and fusarium. Most of the fungi found in indoor air are able to obtain the nutrients they need from dead, moist organic material. Wood, paper, soft furnishings , dust, cooked and raw foods can provide ample opportunity for the fungi to reproduce. Building material, which was left in the rain and outside before use, can harbor viable spores for many years.