The implementation of lower ignition propensity (LIP) regulations, e.g. in the U.S.A., Canada or Europe, has led cigarette manufacturers to develop products with a certain probability of self-extinguishment under standard laboratory testing conditions (ISO 12863).

Usually, LIP products have narrow paper bands along the tobacco rods with low porosity to restrict coal combustion. An increase of the risk of free-air self-extinguishment (FASE) is then unavoidable with LIP compared to non-LIP product designs. The relighting of the cigarette by the smoker after extinguishment increases the quantity of tobacco smoked by puffing, and consequently the exposure to smoke compounds.

In order to better understand the impact of self-extinguishment, a mathematical model reproducing each temporal phases of smoking was developed. The following parameters were considered: tobacco burning rates during and between puffs, tobacco burning rates between and on LIP bands, puffing conditions (puff and inter-puff interval durations, puff volume), filter and paper ventilations, LIP band positions and probability of extinguishment on each band.

A comprehensive description of the mathematical model and the main outputs will be given. Among these outputs, the total quantity of tobacco burned during the puffs for a range of smoking conditions and product designs can be derived. The model has then been used to assess the impact of cigarette self-extinguishment on consumer exposure (see Part II: Simulations).