The table on this slide shows the UL status of electrically-isolated packages that ST makes for Triacs. These include the isolated TO220, the TOP3I, the RD91, and the ISOWATT220.  The first three are 2,500 V isolation and the last molded package, a plastic package device is 1,500 V.  All of the plastic resins used are flammability rated compliant to UL94-V0.