A filler cloth includes cellulosic fibers treated with a flame retardant chemistry such that the filler cloth has a char length of less than about nine inches when tested in accordance with NFPA 701, such that thermal shrinkage of the filler cloth at 400° F. is less than about 35% in any direction, and such that the filler cloth maintains flame and heat resistant integrity when impinged with a gas flame in accordance with testing protocols set forth in Technical Bulletin 603 of the State of California Department of Consumer Affairs. The filler cloth cellulosic fibers are treated with a flame retardant chemistry such that the filler cloth has a Frazier air permeability of less than about 400 cfm and a thermal resistance rating of at least about 3 when tested according to NFPA 2112.