Abstract: Non-burning, non-dripping instant set microcellular polyurethanes involving an isocyanate-terminated reaction product of polyisocyanate with low molecular weight polyether polyol or polyol blends in the presence of other ingredients such as inert liquids with boiling points above about 150.degree. Celsius and accelerating agents for urethane formation. Specifically, this invention provides an improved mode for flame retarding polyurethane compositions by incorporating a mixture of dibromoneopentyl glycol (DBNG) or its esters and a non-reactive flame retardant plasticizer when dissolved or dispersed into the urethane polymer. Molecular sieves are included, which enhance char formation. The compositions have applications with stringent fire retardancy standards, such as electrical insulators, industrial housings, annular spacers, decorative objects, furniture or furniture components, gear and machine components, agricultural components and other related areas.