Fire Alarms in Buildings (2.0)

[ThreePhaseEel]

@NOTIFIER

My high school has two detectors (both smoke!) on the same ceiling tile in some rooms. They only do this in rooms that aren’t sprinklered, and in the science classroom.

I wonder if it was originally built (or alarmed) before ionization-type system detectors were phased out, so they had one ionization and one photoelectric detector in a cross-zoned/coincidence setup in those rooms?