Section 905 requires automatic sprinkler systems in buildings exceeding certain area and occupancy thresholds. All Group R occupancies (residential) exceeding 5,000 square feet require sprinklers. Group B occupancies exceeding 5,000 square feet of floor area require sprinklers. Basements of all buildings exceeding 1,000 square feet typically require sprinklers. Kitchens, laundries, and areas with high fire hazard require sprinklers. Buildings with sufficient water supply from municipal mains can use wet-pipe systems (water-filled pipes). Buildings with unreliable water supply or cold climates use dry-pipe systems (air-filled pipes with water supply valve).