Ignition Propensity Testing at Different O2 Concentrations

Abstract

Ignition propensity of cigarettes on soft furnishings is a function of oxygen availability. Oxygen availability, in turn, depends on air movement, and substrate permeability and geometry. Experiments are described where oxygen concentrations over a range from 14 to 36% were used to control oxygen availability and thereby simulate the effects of the other above named parame ters. The experiments were carried out with two cigarettes (high and low tobacco density and paper permeability), two fabrics (Denim and California Standard, both treated with a range of levels of potassium acetate to obtain an array of different ignitabilities), and two configurations (Flat and L). Each cigarette was characterized in terms of an Ignition Oxygen Level (IOL) (minimum O2 concentration required for ignition) and an Extinction Oxygen Level (EOL) (maximum O 2 concentration below which the cigarettes self- extinguish). The IOL is a function of fabric ignitability, and the EOL is a func tion of fabric permeability. When the results are plotted on a grid of Fabric Ig nitability (FI) versus Oxygen Availability (OA) three domains result: (1) combinations of FI and OA where ignitions take place, (2) combinations of FI and OA where the cigarette self-extinguishes, and (3) combinations of FI and OA where the cigarette burns its whole length without causing an ignition. The experiments demonstrated that when cigarettes are ranked according to ignition propensity, the rankings can reverse depending on test conditions. Thus, of the two test cigarettes, the high density/paper permeability cigarette was more ignition-prone under conditions of limited oxygen availability, whereas the low density/paper permeability cigarette became more ignition- prone as oxygen availability increased.