More than 40 Fire and Rescue NSW (FRNSW) firefighters were called in to attack the blaze which broke out in the two-level facility on Birmingham Avenue around 11.20am.
During the early stages of the fire, three detainees on the top floor smashed windows and jumped onto mattresses below in an effort to escape the smoke.
They were assessed at the scene by paramedics, as were 12 staff who sustained smoke inhalation.
Firefighters quickly contained and extinguished the fire, stopping it from spreading to other parts of the building.
