Mathematical models to analyse the effect of physical properties of cigarettes on the propensity of the cigarette to ignite cellulosic fabrics

A series of 37 cigarettes were analysed to develop a model, based on cigarette physical properties, to predict the ignition propensity of the cigarettes towards cellulosic fabrics. The properties used were: cigarette circumference (in mm), tobacco packing density (in g cm−2), paper permeability (in CORESTA units) and the presence or absence of citrate additives in the paper (used independent of concentration, although typical additions range from 0.5 to 0.8 wt%). Two empirical models were developed, one for low and medium paper permeabilities, and one for very high paper permeabilities (above 50 CORESTA units). The latter exceed the paper permeability of most commercial cigarettes, and have medium to high ignition propensities. Thus, they are probably only of interest from the point of view of a mathematical curiosity. The former model, however, addresses cigarettes in the range where commercial cigarettes are potentially viable. The resulting ignition propensities exhibited cover the entire feasible range, from 0% to 100%. Both models predicted the ignition propensities of the tested cigarettes quite well, within an error range which did not exceed 30% for any cigarette. Physical rationales are presented for the effects of the variables used. However, the rationale for the discontinuity in ignition propensity found for the cigarettes with extremely high paper permeability is less clear. One explanation is that there is probably excess oxygen present so that a fuel/oxygen mixture is obtained with a ratio which is less than the lower flammability limits and is too lean to support combustion. However, further analysis of this issue is warranted. The empirical model for low and medium paper permeability cigarettes is potentially useful for developing cigarettes with lower ignition propensity, since it is a practical way of combining the individual properties that most heavily affect cigarette ignition propensity. © 1997 by John Wiley & Sons, Ltd.