NOTE This standard covers engineered mechanical smoke control systems that use fans, dampers, and dedicated controls to manage the movement of smoke during a fire event. Smoke control is the active counterpart to passive compartmentation: it uses pressure differences and directed airflow to keep tenable conditions on exit paths and to limit smoke migration while occupants evacuate and firefighters respond. The work of this standard includes stairwell pressurization, elevator hoistway pressurization, zoned smoke control, and atrium or large-volume exhaust systems, with their fans, dampers, ductwork interfaces, listed control panels, and the firefighter's smoke control station. (1.1)

NOTE This standard does not cover the following, which are specified elsewhere and are referenced here only at their interfaces with the smoke control system: (1.5)

NOTE Related work is specified in Hvac Fans, Louvers And Dampers, Fire Alarm Systems, Building Automation System, and Testing Adjusting And Balancing. (1.6)

NOTE The following terms apply to this standard: (2.1)

NOTE The publications listed below form a part of this standard to the extent referenced. The edition adopted by the authority having jurisdiction governs; where no edition is adopted, the most recent edition applies. (3.1)

NOTE NFPA 92 is the primary design and acceptance standard for engineered mechanical smoke control and governs pressure differences, exhaust rates, and testing. The edition in widest current adoption is the 2021 edition; a 2024 edition has been published and is entering adoption, and the edition referenced by the authority having jurisdiction shall be confirmed before design. (3.2)

NOTE The applicable design and listing standards include the following. (3.3)

NOTE The smoke control system is a life-safety system whose failure modes are not apparent during normal building operation; rigorous qualification, listing, and inspection are therefore the principal assurance that the system will perform when called upon. (5.1)

NOTE A confusion between fire dampers and smoke dampers is a recurring and consequential error: a fire damper closes on heat to maintain a rated barrier and is not a smoke damper, and a smoke damper controls smoke leakage and does not by itself maintain a fire rating; where both functions occur at one opening a combination damper carrying both listings is required. (5.1.5)

NOTE The selection of smoke control method follows from occupancy, building geometry, and the specific code trigger, and it determines every downstream equipment and control decision; it shall be fixed in the basis of design before equipment is selected. (6.1)

NOTE The 30 lbf door force limit caps the pressure difference that a stairwell can sustain, because a single high-mounted injection point over-pressurizes the lower floors of a tall shaft; tall stairwells therefore require multi-injection or variable-volume designs to distribute pressure and stay within the force limit. (6.1.4)

NOTE The design fire heat release rate used for plume and exhaust calculations shall be documented and justified in the basis of design, because exhaust rate is highly sensitive to the assumed fire size and an unjustified default value yields an under- or over-designed system. (6.1.7)

NOTE Stairwell pressurization keeps a positive pressure in the exit stair relative to the building so that smoke cannot enter the protected egress path; the engineering challenge is holding that pressure uniformly over the height of the shaft without exceeding the door force limit at any floor. (7.1)

NOTE Elevator hoistways connect every floor of a building through a continuous vertical shaft and can act as a chimney that distributes smoke building-wide; pressurizing the hoistway holds smoke out of the shaft and protects the elevators used by occupants and the fire service. (8.1)

NOTE Elevator hoistway pressurization shall be provided where required by the adopted building code, including high-rise and underground conditions; omitting hoistway pressurization where the code triggers apply is a common and consequential design oversight. (8.2)

NOTE Fans serving a smoke exhaust stream may handle hot smoke for the duration of the event, so they are not ordinary HVAC fans: they must be rated, classified, and factory-tested to run at elevated temperature without failure of bearings, drive, or motor. (9.1)

NOTE The AMCA 99 temperature class code shall be cited explicitly in the equipment schedule in addition to the UL listing, because the temperature class defines the maximum operating temperature and duration the fan is rated for. (9.1.2)

NOTE Specifying a standard comfort-HVAC fan for smoke exhaust service is a defect: such a fan lacks the temperature-rated bearings, drive, and motor placement required for hot smoke and will not carry an AMCA 99 elevated-temperature classification. (9.1.3)

NOTE Fans and fan accessories common to comfort and smoke service shall additionally comply with Hvac Fans. (9.1.7)

NOTE Dampers in a smoke control system either hold smoke out of protected paths or direct exhaust along the intended route, and their leakage and temperature rating must match the assumptions in the smoke control model or the system will not achieve its design pressures. (10.1)

NOTE The smoke damper leakage class shall match the barrier leakage assumed in the smoke control design, because a leakier damper than assumed defeats the pressure differential the design relies on. (10.1.2)

NOTE Smoke damper leakage classes are defined by ANSI/AMCA 500-D, where Class I is the tightest and Class III the loosest; Class I or Class II is typical for smoke control service. (10.1.3)

NOTE Smoke dampers on an exhaust path that may carry hot smoke shall be rated for elevated temperature, because exhaust smoke in a fully developed fire can exceed the standard 250°F rating and a standard-rated actuator may fail in service. (10.1.5)

NOTE Dampers, sleeves, and access provisions common to general HVAC service shall additionally comply with Louvers And Dampers. (10.1.9)

NOTE The smoke control design models the building envelope and its internal barriers as a network of leakage paths, and the achieved pressure differences depend directly on the as-built leakage of doors, walls, and penetrations matching the modeled values. (11.1)

NOTE Artificial bottom seals shall not be installed on doors in pressurized installations, because such seals are prohibited by NFPA 105 for these assemblies and can mask leakage assumed in the design. (11.1.2)

NOTE As-built smoke barrier leakage shall be consistent with the values assumed in the smoke control design; field hardware, door undercuts, and unsealed penetrations frequently exceed design assumptions and cause acceptance pressure differences to fail. (11.1.3)

NOTE Smoke control ducts operate at the elevated pressures the fans develop and must hold those pressures with low leakage, because duct leakage is a direct loss of the airflow the design depends on and is checked by a dedicated pressure test. (12.1)

NOTE General HVAC duct sealing classes alone are insufficient for smoke control, and the duct leakage requirement and pressure-test condition shall be cited explicitly so that the duct is tested to the smoke control criterion rather than only a general sealing class. (12.1.3)

NOTE The control panel is the brain of the system and the FSCS is the fire service's hands on it; both are life-safety listed equipment, and the boundary between the smoke control controls and the fire alarm system is a frequent source of interface gaps that must be coordinated and assigned. (13.1)

NOTE A non-dedicated system that reconfigures shared HVAC equipment for smoke control shall provide UL 864 UUKL-listed controls for all shared components, because standard building automation controls on shared equipment used for smoke control do not satisfy the listing requirement and will be rejected at inspection. (13.1.3)

NOTE The division of the FSCS scope between the fire alarm installer and the mechanical controls installer shall be coordinated and assigned so that programming, wiring, and status interfaces are complete with no gaps. (13.1.9)

NOTE Fire alarm initiation, detection, and interface devices that activate the smoke control system are specified in Fire Alarm Systems, and the smoke control interface with general building controls is coordinated with Building Automation System. (13.1.10)

NOTE The sequence of operation translates a detected fire into the correct fans running, dampers positioned, and barriers pressurized; it must be written explicitly for every mode because gaps in the sequence surface as requests for information during commissioning rather than as buildable instructions. (14.1)

NOTE The weekly automatic self-test sequence and its programming scope shall be included in the smoke control specification and controls programming, because omitting the self-test sequence is a frequent gap that generates requests for information at commissioning. (14.1.5)

NOTE A smoke control system that loses power during a fire is no system at all, so its fans and controls are placed on the building's emergency power so they continue to run when normal power fails. (15.1)

NOTE The emergency power supply system Type and Class shall be verified to comply with NFPA 110 for the smoke control load, because connecting smoke control to a standard normal/standby transfer without confirming the required Type and Class is a code deficiency. (15.1.2)

NOTE Acceptance testing is the moment the design assumptions meet reality; it measures the actual pressure differences, door forces, and exhaust flows and is the only proof the engineered system performs as intended. (16.1)

NOTE The integrated testing scope per NFPA 4 shall be included in the project schedule and commissioning plan, because the integrated test is required before occupancy and is frequently overlooked until late in construction. (16.1.6)

NOTE Air balancing of smoke control airflows shall be coordinated with Testing Adjusting And Balancing. (16.1.9)

NOTE Damaged listing labels or rating tags shall be cause for rejection, because the listing and temperature rating cannot be verified without them. (18.1.3)