Toxins accumulate in buildings from many sources: building materials (wood, paint, carpeting, flooring, etc.) furniture, as well as cleaning and beauty products. Heating/cooling systems may also contribute to toxic exposure.
One of the biggest sources of volatile organic compounds (VOCs) is manufactured wood building products: structural plywood, wall paneling, and particleboard being three of the most common. The adhesives used in these products are notorious for giving off VOCs continuously and over a long period of time. Wall and floor finishing materials are also toxic chemical sources, as well as paint and one and two-part floor finishes: urethane, varnish, lacquer, shellac, etc. Fossil fuel burning devices such as heating furnaces, water heaters, and stoves can produce carbon monoxide and carbon dioxide.
Domestic consumer cleaning products are a major contributor to household toxins: laundry detergens and bleach, bathroom cleaners, kitchen cleaners, and even soap and shampoo. Many other consumer products are fabricated from toxic materials, items such as: raincoats, umbrellas, air fresheners, etc. Carpeting often has fire retardants in it that have been noted as sources of indoor pollution. Pet dander, dust and odors are held amidst carpet fibers and can be a constant source of airborne irritants. Office equipment such as copy machines, printers and fax machines can be a source of airborne pollutants as well.