Abstract: This disclosure teaches a structural, fire extinguishing and ventilating system for use in building construction. Parallel joists have tubular lower chords through which fire extinguishing water is circulated and from which a perforated ceiling depends to form an upper enclosure for a room. Ventilating air ducts are positioned between the joists so that the ventilating air passes over the tubular lower chords in noncontact heat exchange relationship with the fire extinguisher water and the air then passes downward through the perforated ceiling to the room.