Abstract: A method for making fire retardant material including fire retardant cellulosic insulation. The method includes an arrangement for adding fibers of one or more feedstocks and a fire retardancy chemical compound to a mixer prior to fiber drying. The fibers are separated prior to or during mixing with the fire retardancy chemical compound. The feedstock may include old newsprint (ONP), old corrugated containers (OCC), and/or other cellulose-based materials. The method further includes retaining the separated fibers feedstock and the chemical compound together for enough time to ensure adherence and impregnation of enough of the chemical to and in the fibers after the drying process. Separated fibers may be partitioned/classified prior to and/or after treatment.