Styrene gas release from heated polystyrene

[peleur]

Does anyone have information on the amount of styrene gas that is likely to be released when polystyrene roof insulation on top of a steel deck roof is heated from a fire below? more broadly, is all polystyrene likely to decompose into combustible gases, or should I expect a significant fraction of the original mass to remain in place in the form of a residue ?

Thanks for any information.