Five-hundred popular upholstery fabrics were obtained from commercial fabric shops in North Carolina. The ignitability of each upholstery fabric was characterized using a particular smoldering cigarette in a specified protocol with six replications. If one or more of the smoldering cigarettes resulted in smoldering of the fabric, the fabric was classified as ignitable. Of the 500 fabrics, 355 were found to be non-ignitable and 145 were classified as ignitable. The differences between the properties of ignitable and non-ignitable fabrics were examined. The results show that the upholstery fabrics' contents of sodium and potassium salts, their concentrations of cellulosics, and their basis weights (areal densities) correlate with ignitability. An aqueous rinse of upholstery fabrics rendered them substantially non-ignitable by the smoldering-cigarette used in this study.

Upholstery fabrics for residential use were obtained from various fabric shops and manufacturers' catalogs. Screening was conducted with four experimental cigarettes of varying design. By the National Institute of Standards and Technology (NIST) cotton duck mockup method, two of the cigarettes display "low" ignition propensity and two show "high" ignition propensity. Of the fabrics obtained for this study, 316 smoldered when in contact with at least one of the experimental cigarettes. Further examination within this set of upholstery fabrics showed once again that cigarette ignition propensity ranking are dependent on fabric characteristics. The number of fabrics that showed ignition propensity rankings opposite to the NIST test "ranking" was similar to the number that agreed with it. That is, on the fabrics with rankings opposite to the NIST ranking, cigarettes of "low" ignition propensity by the NIST test showed more ignitions than cigarettes of "high" ignition propensity by the NIST test. These results are consistent with those of a previously published study with a smaller set of ignitable fabrics. Fabric weight was a key factor in determining fabric ignition behavior; two of the cigarettes showed increasing ignition propensity and two showed decreasing ignition propensity with fabric weight. For the majority of fabrics, however, cigarette design was unimportant in determining ignition behavior; that is, no differences in ignition behavior were observed with the different cigarette designs. The physical and chemical properties of the cotton duck fabrics of the NIST test are such that they repre-JOURNAL OF FIRE SCIENCES, VOL.

The time and heat flux required for the initiation of smoldering combustion in cellulosic fabrics depends on the properties of both the environment and the fabric. In the environment, there must be sufficient oxygen to support smoldering combustion and there must be sufficient heat to raise the temperature of the fabric to the point where combustion becomes self supporting. The critical factors for the cellulosic fabrics are the potassium and/or sodium ion content and the thermal characteristics of the fabric. A series of simple weave, raw cotton fabrics, commonly referred to as cotton ducks, and an upholstery fabric were examined. The requirements for the initiation of smoldering combustion were similar for both the ducks and the upholstery fabric. However, the situation for the upholstery fabric was complicated by the non-homogeneous distribution of ions in the material and spatial variations in fabric thickness and basis weight. Also, for fabrics with potassium and sodium ion contents in the range of approximately 1500 to 2500 ppm, there was an increased sensitivity to the environmental factors.

In order to understand how the raw materials and processing contribute to the performance of the products, a mathematical model of pressure drop and ventilation in a lit cigarette has been developed. The model can be used to predict these parameters based on the geometry and properties of tobacco rod and filter, such as cigarette circumference, paper permeability, and design of filter vent rows. The model can be used to evaluate the contributions of variable components to the changes of pressure drop and ventilation of a lit cigarette.

Cigarette filters remove both particles and condensable vapours from tobacco smoke aerosols. The particulate contribution to filtration can be isolated by allowing the smoke aerosol to attain thermal equilibrium before it is introduced to the filter. Such experiments show the effects of filter length, filter pressure drop, and aerosol flow rate on particulate filtration. The relative roles of diffusion, impaction, and interception on particle removal have been examined. The extent to which vapour condensation occurs in filters has been found to be dependent on the length to which the tobacco rod has been smoked and independent of the pressure drop of the filter.