pyrostat

/ˈpaɪrəˌstæt/
noun
  1. A device that automatically controls a fire alarm or fire extinguishing system.
    • Every floor of the hotel is equipped with a pyrostat for early fire detection.
    • The technician tested the pyrostat to ensure it would activate in an emergency.
    • The building's pyrostat triggered the sprinklers when smoke was detected.