materials used are more fully described as follows tetrakis hydroxymethyl phosphonium sulfate thps available from albright amp wilson inc under the name of retardol s and from american cyanamid under the name pyroset tkow is a pale straw colored liquid that is miscible with water and has a pungent odor several related compounds can be used in place of thps including tetrakis hydroxymethyl phosphonium chloride thpc available under the name of retardol c from albright amp wilson and tetrakis hydroxymethyl phosphonium oxalate available as pyroset tks from american cyanamid company the urea precondensate forms of any of the above can also be used thps when mixed with urea and heated strongly form a relatively insoluble polymer containing both phosphorus and nitrogen inside and around the cotton fibers the durability of this polymer is increased further by oxidizing the phosphorus with hydrogen peroxide and the odor of phosphorus compounds is minimized or eliminated the examples presented below compare the results of a single pass 34 conventional 34 flame retarding process for 100 cotton with those for a double pass procedure which is a subject of the present invention the examples show the results of repeated industrial laundering on functional characteristics of the treated laundered cotton fabrics the results of repeated laundering.