| Cigarette smoke is made up of both a gas phase and | | | | They specifically construct cigarettes in ways to |
| particulate phase. Together they include more than | | | | control a wide range of factors: keeping the cigarette |
| 4,000 substances. Automatic cigarette-puffing | | | | burning between puffs, reducing spoilage of the |
| machines have been devised to collect and to study | | | | tobacco, altering the flavor of the smoke, and |
| smoke. The smoke is separated into the gas and solid | | | | controlling the amounts of substances (tar and nicotine) |
| (particulate) phases by passing it through a filter pad | | | | measured by government agencies. |
| (Cambridge filter), which traps particles larger than one | | | | The porosity of cigarette paper is specifically controlled |
| micrometre. And collects the rest (gas phase) in a | | | | to regulate the amount of air that passes through and |
| storage tank. The machines are calibrated to smoke | | | | dilutes the smoke. Porosity also affects how rapidly |
| the cigarettes the way a typical smoker might smoke | | | | the cigarette burns. Phosphates are added to the |
| them. | | | | paper to ensure steady and even burning. |
| During a puff, the un-burned cigarette is comprised of | | | | Several kinds of additives are present in the tobacco |
| many organic components (tobacco leaves, paper | | | | itself. One type of additive is called humectants. |
| products, sugars, nicotine) and inorganic (water, | | | | Humectants are chemicals that help retain the moisture |
| radioactive elements, metals) materials. The tip of the | | | | (humidity) of the tobacco. This is important in how the |
| burn-in cone in the centre of the cigarette reaches a | | | | tobacco burns. Humectants also affect the taste and |
| temperature of nearly 1,093 degrees C. (2,000 degrees | | | | temperature of the smoke. The most commonly used |
| F.) during each puff. This tiny blast furnace results in a | | | | humectants are glycerol, D-sorbitol, and diethylene |
| miniature chemical plant, which uses the hundreds of | | | | glycol. Humectants comprise a new per cent of the |
| available materials to produce many more. In fact, | | | | total weight of the tobacco. |
| some of the most important parts of tobacco smoke | | | | Another type of additive is called a casing agent. This |
| (including tar and carbon monoxide) are not even | | | | helps blend the tobacco and hold it together. It also |
| present in an unburned cigarette, but are produced | | | | affects the flavor of the smoke and how quickly the |
| when a puff is taken and the cigarette burns. | | | | tobacco burns. Most commonly used casing agents |
| Study of the smoke is made even more complicated | | | | include sugars, syrups, licorice, and balsams. The |
| since there are both side stream and mainstream | | | | amount of casing agents used ranges from about 5% |
| smoke which must be separately collected and | | | | of the total weight of the tobacco in cigarette tobacco |
| studied. The mainstream smoke is collected from the | | | | to about 30% of the weight of pipe tobacco. |
| stream of air passing through the centre of the | | | | Specific flavoring agents are also added to the |
| cigarette. It is filtered by the tobacco itself and perhaps | | | | tobacco to control the characteristic taste of a |
| further by a filter. It is also diluted by air passing through | | | | cigarette. These include fruit extracts, menthol oils, |
| the paper (most modern cigarettes also have tiny | | | | spices, coca, aromatic materials, and synthetic |
| ventilation holes which further dilute the smoke). | | | | additives. Flavor is also controlled by curing processes |
| Side stream smoke is that which escapes from the tip | | | | and, of course, the type of tobacco itself. |
| of the cigarette. It is not filtered by the cigarette and | | | | A variety of other substances are added at various |
| results from a slightly cooler burning process at the | | | | stages of tobacco processing to retard spoilage. In |
| edge of the burning cone. Since the tobacco is | | | | addition, metals such as nickel and potassium are |
| therefore burned less completely, the side stream | | | | taken up from the soil, as are pesticides and fertilizers |
| smoke has more particulate (unburned material) in it. | | | | used in tobacco farming. There are also radioactive |
| Cigarette Engineering | | | | elements such as potassium-40, lead-210, and |
| The above process is complicated even further by the | | | | radium-226, which result from fallout and the natural |
| engineering efforts of the tobacco manufacturers. | | | | background. |