This is in contrast to the smoke produced by a burning cigarette, which contains a wide range of chemicals because its burning tip undergoes a very wide range of temperatures, from ambient to about 1000°C. Attempts to selectively modify this complex combustion process in conventional cigarettes have not been successful.
By heating tobacco at a specific temperature in the range seen in a burning cigarette, Baker established that, at lower temperatures of between 100 and 200°C, water and volatile substances including flavour molecules loosely bound to the surface of the tobacco leaf are the first to be released through distillation and evaporation. Simple pectins and sugars in tobacco may also begin to decompose. Although the boiling point of nicotine is around 247°C, nicotine starts to vaporize and enter the aerosol at temperatures from 170 to 200°C[5-6]. At 300 to 400°C, some tar components start to form from the breakdown of cellulose and other structural components of tobacco, but it is not until temperatures of more than 400°C that the main pyrolysis occurs. Leaf components such as amino acids and esters decompose between 400°C and 600°C, and carboxymethylcelluloses and carbonates between 600°C and 900°C, producing the bulk of the carbon monoxide, polycyclic aromatic hydrocarbons and other combustion products that form the tar in cigarette smoke.
To design a tobacco heating product that produces significantly fewer of the toxicants formed by pyrolysis and combustion reactions, tobacco in a tobacco heating product is typically heated to around 250°C only. This allows nicotine to vaporize out of the tobacco leaf, but pyrolysis and combustion does not occur. The fraction of toxicants and their levels in tobacco heating-device emissions will depend on the operating temperature and the tobacco blend used.