These items are often manufactured with formaldehyde which is released as a gas. The excreta and body parts of dust mites are a common allergen. They are a particular problem in bedrooms. This metal is found in plumbing pipes, older paints and blinds. Some of these gases are suspected carcinogens.
Gas stoves are a source of combustion by-products.
Open fires can produce ash dust, carcinogenic tars, and combustion by-products like carbon monoxide and nitrogen oxides. Wood paneling is often manufactured with formaldehyde. The treated fabrics of draperies can contain formaldehyde. Curtain folds also collect dust. Tobacco smoke contains 43 known carcinogens.