Section 909.1/Smoke Control Systems
IBC 909 covers smoke control system design including pressurization and exhaust methods, rational analysis, and acceptance testing for atriums, underground buildings, and high-rise buildings.
IBC 909 requires smoke control systems in specific building configurations: atriums connecting two or more stories (per Section 404.5), underground buildings with floor levels more than 30 feet below exit discharge (per Section 405), high-rise buildings (per Section 403), and covered and open mall buildings under certain conditions. Two basic approaches are permitted: the pressurization method (Section 909.6), which maintains a pressure differential across smoke barriers to prevent smoke migration, and the exhaust method (Section 909.8), which mechanically removes smoke from the fire area. Section 909.4 requires a rational analysis documenting the design fire size, smoke production rate, smoke layer depth, and system capacity. Section 909.18 requires acceptance testing before occupancy, including verification of airflow rates, pressure differentials, and system activation from fire alarm inputs, sprinkler waterflow, and manual controls.
Why this section exists
Large open spaces like atriums and underground floors allow smoke to spread across multiple stories, overwhelming the egress system before occupants can evacuate. Smoke control systems keep egress paths tenable by either pressurizing stairways and refuge areas to exclude smoke or by exhausting smoke from the fire floor to maintain a clear layer below the smoke. Without smoke control, an atrium fire can fill multiple stories with smoke in minutes, making exit stairways unusable. The rational analysis requirement ensures the system is engineered for the specific building geometry and expected fire characteristics, not just sized by rule of thumb.
What plan reviewers look for
Plan reviewers check the mechanical drawings for the smoke control system layout including dedicated exhaust fans, supply fans, smoke dampers, and ductwork. They verify the rational analysis documents the design fire (typically 5,000 Btu/s for a sprinklered atrium), smoke production rate, and required exhaust rate. They check that the system activates from fire alarm initiating devices, sprinkler waterflow switches, and a manual firefighter smoke control panel. They verify the dedicated smoke control panel location and annunciation. They check that the sprinkler system is coordinated with the smoke control system assumptions. They confirm acceptance testing procedures are specified.