
Cigarette smoke removal quickly becomes such a pesky problem because tobacco smoke is made up of gases and particulates, including carcinogens and heavy metals, like arsenic, lead, and cyanide. Sticky, toxic substances, like nicotine and tar, cling to walls and ceilings. Gases are absorbed into carpets, draperies, and other surfaces. Tobacco residue is present in dust and on surfaces throughout places where smoking has occurred. This toxic sticky residue can reemit (off-gas) back into the air and recombine to form harmful substances that remain at high levels long after smoking has stopped.
(Source: no-smoke.org)