As Oakland firefighters pulled up to the burning Ghost Ship warehouse the night of Dec. 2, they weren’t exactly sure what they were dealing with — whether anyone was trapped or what they would encounter inside — but they didn’t assume it was a vacant building. Public safety officials in Oakland have long been aware that people live and party in warehouses — some firefighters say they can tell whether one is inhabited just by looking at its exterior. But even if the Fire Department didn’t know the Ghost Ship had people living in it, as Fire Chief Teresa Deloach Reed said, firefighters treated the blaze as they would any other burning building: They assumed someone was stuck inside.