No air purifier can completely eliminate smoke, because particles of tobacco smoke are too small to be trapped by them. However, some air purifiers can reduce smoke from the air as well as dust and pollen.
The most effective air purifiers are those with filters. Air purifiers that have no filters pull particles out of the air by relying on electrical charges, producing low levels of ozone as a result. Ozone irritates lungs, makes asthma worse and can even cause lung damage. Air filters that produce ozone are very ineffective at removing smoke from the air. The best way to keep smoke out of the air is to prohibit smoking in the building.