Formaldehyde is use in the carpeting and other amenities. It should be avoided at all costs and IS toxic especially to pets. Not all manufacturers use it and a statement from the manufacturer should be made available to the buyer. Styrene is used in fiber glass and is a and is not proven to be a carcinogen in its liquid form, but I don't know of any ill effects from the gas it gives off. Again a reputable manufacturer should provide a list of gasses emitted in the first year. After several months most gasses are depleted.