Open fireplaces can produce ash dust, carcinogenic tars as well as carbon monoxide and nitrogen oxides.
Plastic wallpapers can emit VOC’s and wood panelling is often manufactured with formaldehyde. Formaldehyde may also be found in curtains and drapes. These commonly collect dust.
Tobacco smoke contain 43 carcinogens and we now know the dangers of second-hand smoke expecially for children.
Carpets can be a source of formaldehyde and harbour dust, dust mites, animal dander and skin flakes which are a common source of allergens.
Radon carries radioactive particles that can be a dangerous cuase of lung cancer.