Abstract: The equipment of absorbing HCN was used to study the effect of the type of fire retardant and contents on the yield of HCN in the process of polyurethane foam pyrolysis. It was found that NH4Cl, (NH4)2SO4, and (NH4)3PO4•3H2O increased the HCN yield, while MgCl2, C2H4N4, NH4H2PO4 , KH2PO4, and Na2B4O7•10H2O reduced the HCN yield. Particularly, when the content of Na2B4O7•10H2O was 23.08 %，the release amount of HCN was 3.2915 mg/g，which was 38.33% that of plain polyurethane foam.

Key words: polyurethane foam, hydrogen cyanide, flame retardant, thermal degradation