Water based liquid fire retardant for use in cellulose insulation

A method of producing a fire-retarded cellulose fiber material, comprising:

• providing an aqueous fire-retardant composition comprising phosphoric acid, ammonium sulfate and water, and optionally, one or more non-fire retardant additives, the aqueous fire-retardant composition having a pH of 1.75 to 2.6, and the phosphoric acid and the ammonium sulfate having a weight ratio of 1:19 to 5:15;
• applying the aqueous fire-retardant composition to a cellulose material to produce a wetted, fire retardant-treated cellulose material comprising from 5 wt % to 15 wt % of a sum weight of the phosphoric acid and the ammonium sulfate, based on a total weight of the wetted, fire retardant-treated cellulose material;
• drying the wetted, fire retardant-treated cellulose material to produce a dried, fire retardant-treated cellulose material comprising phosphoric acid and ammonium sulfate absorbed, adsorbed and/or adhered to the cellulose material;
• processing the dried, fire retardant-treated cellulose material in size to produce a reduced size, fiberized, fire-retarded cellulose fiber material;
• and
• removing dust material from the reduced size, fiberized, fire-retarded cellulose material to remove from 15 wt % to 30 wt % of an overall weight of the reduced size, fiberized, fire-retarded cellulose material in the form of dust particles.