Filter cigarette

A cigarette filter, also known as a filter tip, is a component of a cigarette, along with cigarette paper, capsules and adhesives. It does not make cigarettes less unhealthy. — Claude Teague, the inventor of the colour-changing filter A cigarette filter, also known as a filter tip, is a component of a cigarette, along with cigarette paper, capsules and adhesives. It does not make cigarettes less unhealthy. The filter may be made from cellulose acetate fibre, paper or activated charcoal (either as a cavity filter or embedded into the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos have also been used in cigarette filters. The acetate and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). In laboratory testing, filters have been shown to reduce 'tar' and nicotine smoke yields up to 50%, with a greater removal rate for other classes of compounds (e.g., phenols), but are ineffective in filtering toxins such as carbon monoxide. However, most of these measured reductions occur only when the cigarette is smoked on a smoking machine; when a human smokes them, deliveries remain similar with or without a filter. Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist. The near-universal adoption of filters on cigarettes has not reduced harms to smokers and lung cancer rates have not declined. Filling a given length of cigarette with filter is cheaper than filling it with tobacco. In 1925, Hungarian inventor Boris Aivaz patented the process of making a cigarette filter from crepe paper. From 1935, a British company began to develop a machine that made cigarettes incorporating the tipped filter. It was considered a specialty item until 1954, when manufacturers introduced the machine more broadly, following a spate of speculative announcements from doctors and researchers concerning a possible link between lung diseases and smoking. Since filtered cigarettes were considered 'safer', by the 1960s, they dominated the market. Production of filter cigarettes rose from 0.5 percent in 1950 to 87.7 percent by 1975. Between the 1930s and the 1950s, most cigarettes were 70 mm (~2 3/4 in) long. The modern cigarette market includes mainly filter cigarettes that are 80 mm (in boxes; ~3 1/8 in), 85 mm (in softpack; ~3 3/8 in), 100 mm (~3 15/16 in), or even 120 mm (~4 3/4 in) long. Cigarettes filters were originally made of cork and used to prevent tobacco flakes from getting on the smoker's tongue. Many are still patterned to look like cork. Cellulose acetate is made by esterifying bleached cotton or wood pulp with acetic acid. Of the three cellulose hydroxy groups available for esterification, between two and three are esterified by controlling the amount of acid (degree of substitution (DS) 2.35-2.55). The ester is spun into fibers and formed into bundles called filter tow. Flavors (menthol), sweeteners, softeners (triacetin), flame retardants (sodium tungstate), breakable capsules releasing flavors on demand, and additives colouring the tobacco smoke may be added to cigarette filters. The five largest manufactures of filter tow are Hoechst-Celanese and Eastman Chemicals in the United States, Rhodia Acetow in Germany, Daicel and Mitsubishi Rayon in Japan.