Cigarette filter

A cigarette filter, also known as a filter tip, is a component of a cigarette, along with cigarette paper, capsules and adhesives. Filters were introduced in the early 1950s.

Filters may be made from plastic cellulose acetate fiber, paper or activated charcoal (either as a cavity filter or embedded into the plastic cellulose acetate fibers). Macroporous phenol-formaldehyde resins and asbestos have also been used. The plastic cellulose acetate filter and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption).

Filters are intended to reduce the harm caused by smoking by reducing harmful chemicals inhaled by smokers. While laboratory tests show a reduction of "tar" and nicotine in cigarette smoke, filters are ineffective at removing gases of low molecular weight, such as carbon monoxide. Most of these measured reductions occur only when the cigarette is smoked on a smoking machine; when smoked by a human, the compounds are delivered into the lungs regardless of whether a filter is used.

Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist.