... usage: essential fireproofing additive in expansive fireretardant coating and fire retardan Ammonium polyphosphate(APP) :a. molecular formula: NH4PO3n ... an essential fireproofing additive in expansive fireretardant coating and fire retardants, used in architecture, shipping, cable field ... architecture, shipping, train, cable.2) Used in fire retardant treat in lignum, veneer, fiberboard, paper, fiber ...