Furniture, Carpets, foam insulation, pressed wood produce VOCs
Tobacco Smoke: Toxic and carcinogenic
Old Paint: Lead
Floor & ceiling tiles, & pipe insulation: Asbestos
Rocks and soil beneath house: Radon
Household Products, pesticides, paints, cleaning fluids: VOCs & other compounds.
Fireplaces, wood stoves: Particulate Matter
Leaky or unvented gas or wood stoves and furnaces, running cars left running: CO.