Cigarettes, cigars and pipes are popular smoking articles which use tobacco in various forms. Many smoking products and smoking articles have been proposed through the years as improvements upon, or alternatives to, the various popular smoking articles.
Many tobacco substitute smoking materials have been proposed, and a substantial listing of such materials can be found in U.S. Pat. No. 4,079,742 to Rainer et al. Tobacco substitute smoking materials having the tradenames Cytrel and NSM were introduced in Europe during the 1970's as partial tobacco replacements, but did not realize any long-term commercial success.
Numerous references have proposed smoking articles which were used to generate flavored vapor and/or visible aerosol. See, for example, U.S. Pat. No. 2,907,686 to Siegel; U.S. Pat. Nos. 3,258,015 and 3,356,094 to Ellis et al.; U.S. Pat. No. 3,516,417 to Moses; U.S. Pat. No. 4,340,072 to Bolt and U.S. Pat. No. 4,474,191 to Steiner.
In European Patent Publication No. 212,234; and U.S. Pat. Nos. 4,708,151; 4,714,082; 4,756,318, 4,793,365, 4,827,950, 4,858,630, 4,893,637, 4,893,639, 4,903,714 and 4,938,238; assigned to R. J. Reynolds Tobacco Co., there are described smoking articles which are capable of providing the sensations associated with cigarette and pipe smoking, without the necessity of burning tobacco and without delivering considerable quantities of incomplete combustion products. Such smoking articles employ an aerosol generating means, physically separate from and in a heat exchange relationship with a fuel element. The aerosol generating means normally includes tobacco in various forms such as densified pellets, tobacco extracts, as well as tobacco flavor modifiers and tobacco flavoring agents and aerosol forming substances such as glycerin.
It would be desirable to provide substantially non-burnable papers or wrappers which encircle at least a portion of the fuel elements of such smoking articles, where the porosity of such wrappers, and therefore the air flow to fuel element, is substantially independent of the physical changes which the wrapper undergoes during smoking and where the wrapper chars rather than burns, leaving a substantial portion of the charred cellulosic content of the wrapper intact during smoking.