A polysulfone having a first polyphenylene sulfone unit (i.e. PPSU unit) based on one biphenol group and one diphenyl sulfone group and a second sulfone unit (i.e. PSU-AF unit) based on one hexafluorobisphenol A group and one diphenylsulfone group. The polysulfone is transparent and has a total heat release and peak heat release of less than 65 kWmin/m.sup.2 and 65 kW/m.sup.2, respectively. Compositions containing the polysulfone and articles made by molding and/or extruding the polysulfone.