Smoke Hazard Management in High-Rise Buildings

What This Requirement Covers

Smoke hazard management in high-rise buildings refers to the design, installation and operation of systems and arrangements intended to limit the spread of smoke, maintain tenable escape routes and protect occupants and emergency responders during a fire. It exists because smoke, rather than flame, is often the principal cause of injury and death in building fires; controlling smoke movement preserves means of egress, reduces exposure to toxic gases and supports firefighting operations. These requirements apply to designers, builders, certifiers, building owners and facility managers of multi-storey and other buildings where occupants cannot easily evacuate to the open air, including required fire-isolated stairways, lobbies, atria, enclosed malls and large fire compartments.

In the Australian regulatory framework these provisions are contained primarily in NCC (National Construction Code) Volume One (the Building Code of Australia for Classes 2-9 and certain multi-class buildings) and supporting Specifications and referenced Australian Standards. Key standards referenced include AS 1668.1 (the specification for mechanical ventilation and air-handling for fire and smoke control), AS 1670.1 (fire detection, warning, control and intercom systems), and other NCC Specifications (for example, Specification 20 - fire detection and alarm, Specification 21 - smoke exhaust systems). Where relevant, state and territory schedules in the NCC may modify or add requirements.

Key Requirements

1. Effective height threshold: Fire-isolated stairways (and associated fire-isolated passageways/ramps) that serve any storey above an effective height of 25 m must be provided with an automatic air pressurisation system for the exit in accordance with AS 1668.1, or alternate access ramps or balconies per D3D6, as set out in NCC Volume One, E2D4. (NCC Volume One, E2D4)
2. Automatic smoke exhaust vs other measures: For certain occupancies and large fire compartments, buildings must provide an automatic smoke exhaust system complying with Specification 21, or where applicable roof-mounted automatic smoke-and-heat vents per Specification 22, or alternative measures such as automatic smoke detection and alarm systems (Specification 20) or an approved sprinkler system (Specification 17). Specific floor-area thresholds apply: e.g., requirements reference fire compartment floor areas such as 2 000 m2, 3 500 m2, or 5 000 m2 depending on building use and volume (NCC Volume One, multiple E2D clauses and Specification 21). (NCC Volume One, E2D and Spec 21)
3. Smoke detection sensitivity and spacing: Smoke detectors used to operate smoke control systems must comply with AS 1670.1 sensitivity requirements. In multi-storey walkways and malls in Class 6 buildings detector sensitivity must not exceed 0.5% smoke obscuration per metre (with compensation for external airborne contamination) and spacing rules such as detectors no more than 15 m apart and not more than 7.5 m from any wall, bulkhead or curtain for enclosed malls are used. (NCC Volume One, Spec 20 / Clause S20 and related E2D content)
4. Air-handling shutdown and smoke dampers: Air-handling systems that are not part of the smoke hazard management system are required to automatically shut down on activation of the smoke exhaust system (subject to limited exceptions). Smoke control systems must either operate in accordance with AS 1668.1 or incorporate smoke dampers at penetrations and automatic shutdown via smoke detectors complying with AS 1670.1 (NCC Volume One, Spec S21 and AS 1668.1 references). (NCC Volume One, S21 and AS 1668.1)
5. Occupant warning integration: Smoke detectors that activate a smoke control system must either be part of the building fire detection system complying with AS 1670.1 or a separate dedicated system complying with AS 1670.1, and must activate the building occupant warning system in accordance with S20C7. For Class 2 and 3 buildings the occupant warning level may be satisfied at the door to a sole-occupancy unit at not less than 85 dB(A) where in-unit measurement is not required. (NCC Volume One, S20C7 / AS 1670.1)
6. Manual controls and emergency interface: Manual override control and indication must be provided adjacent to the fire indicator panel in accordance with clauses 4.11 and 4.13 of AS 1668.1. Manual control for smoke exhaust systems must also be provided at locations normally used by stage managers in theatres, and clear operating instructions must be available for emergency personnel. (NCC Volume One, S21 / AS 1668.1)
7. Power and wiring requirements: Power supply and control wiring for exhaust fans and detection/control/indication circuits must comply with AS 1668.1 (NCC Volume One, S21C7 and S21C8).
8. Sole-occupancy units treated as separate compartments: For air-handling and smoke control system arrangement purposes each sole-occupancy unit in a Class 2 or 3 building is treated as a separate fire compartment (NCC Volume One, S21 commentary/AS 1668.1 cross-reference).
9. References to Australian Standards and NCC clauses:
10. NCC Volume One - E2D4, E2D16-E2D21, S20C7, S21C7, S21C8, Specification 20, Specification 21, Specification 22
11. AS 1668.1 - Mechanical ventilation, air-handling and smoke control system design and installation
12. AS 1670.1 - Fire detection, warning, control and intercom systems
13. Specification 17 - Sprinkler systems (where sprinklers are referenced as alternative mitigation)

Residential vs Commercial

1. Residential (Class 1 and Class 10): Detached Class 1 dwellings and most Class 10 structures are generally outside the smoke hazard management provisions specific to high-rise smoke control systems in NCC Volume One. However, for Class 2 and 3 residential buildings (apartments/boarding houses) the NCC treats each sole-occupancy unit as a separate fire compartment and requires connection of detection and warning systems to smoke control measures where those measures are installed. In multi-storey residential apartment buildings (>25 m effective height) required fire-isolated exits must be pressurised in accordance with AS 1668.1 (NCC Volume One, E2D4).
2. Commercial (Class 2-9): Commercial, institutional and assembly buildings (Class 2 where apartments occur above a podium, Class 3, Class 5-9) are the primary scope for smoke hazard management systems. These buildings are subject to the full suite of requirements - automatic smoke exhaust systems (Specification 21), pressurisation of fire-isolated exits (AS 1668.1), detector sensitivity/spacings, occupant warning integration (AS 1670.1), and alternative mitigation such as sprinklers per Specification 17 when permitted. Floor-area thresholds triggering exhaust or venting requirements (for example 2 000 m2, 3 500 m2, 5 000 m2) typically apply to assembly, mall, exhibition and large open-plan commercial spaces (NCC Volume One, E2D clauses and Spec 21).

Exceptions and Exemptions

1. Smaller single-storey fire compartments may use alternatives: for a single storey building an alternative to an automatic smoke exhaust system may be automatic smoke-and-heat vents complying with Specification 22, or an automatic smoke detection and alarm system complying with Specification 20 where the floor area is within certain thresholds (NCC Volume One, E2D clauses).
2. Sprinklers as an alternative: In some circumstances a compliant sprinkler system (Specification 17) may be accepted as an alternative or partial alternative to smoke hazard management measures for certain floor areas or occupancies, subject to exceptions (e.g., FPAA101D or FPAA101H systems excluded in some references). (NCC Volume One, E2D)
3. State schedules: State and territory Schedules to the NCC may provide concessions or additional requirements; those local variations can operate as temporary exemptions or additional obligations and must be checked in project jurisdiction. See State and Territory Variations below.
4. Equipment exceptions: Small individual room air-handling units with capacity less than 1 000 L/s and certain miscellaneous exhaust systems installed per Sections 5 and 6 of AS 1668.1 may be excluded from automatic shutdown requirements that otherwise apply to larger systems. (NCC Volume One, Spec S21)

State and Territory Variations

1. The NCC is national but each state and territory may include a schedule or amendment that modifies E2D provisions. For example:
2. New South Wales: The NSW variations in the NCC include NSW-specific E2D16-E2D19 provisions for large assembly buildings (exhibition halls, museums, art galleries) with tailored floor-area thresholds and required measures for spaces >2 000 m2 and up to 3 500 m2, and references to automatic smoke exhaust as needed (NCC Volume One, NSW E2D clauses).
3. Queensland, Victoria, WA, SA, TAS, ACT, NT: Each jurisdiction may have additional clarifications or state schedules that affect required smoke control arrangements, pressurisation practice or alternative acceptance of sprinkler systems. Designers must consult the NCC Volume One state schedules (Schedules 4-12) for specific jurisdictional modifications and any relevant state legislation or guidance.

Always verify the relevant NCC state schedule for the project location because local amendments can change thresholds, permitted alternatives or require additional measures for specific building functions.

Practical Compliance Tips

1. Plan smoke control early: Integrate smoke hazard management into the concept design stage - pressurisation, exhaust and detector zoning are difficult to retrofit efficiently in multi-storey buildings.
2. Follow AS 1668.1 and AS 1670.1 precisely: Use the exact system design and detection sensitivity, spacing and wiring practices in AS 1668.1 and AS 1670.1; deviations often cause non-compliances at certification.
3. Check floor-area triggers: Confirm fire compartment floor areas against the NCC thresholds (for example 2 000 m2, 3 500 m2, 5 000 m2) early to determine if automatic smoke exhaust, vents or sprinkler alternatives are required.
4. Treat sole-occupancy units as compartments: In multi-residential buildings treat each apartment as a separate fire compartment when designing air handling and smoke control interfaces; this affects zoning and shutdown strategies.
5. Coordinate HVAC and fire systems: Ensure HVAC contractors, fire services designers and electrical contractors coordinate shutdown, damper control and power supply wiring so that automatic shutdown behaviors operate as intended on detector activation.
6. Provide clear manual controls and documentation: Install manual overrides, labelled controls and concise operating instructions adjacent to the fire indicator panel as required by AS 1668.1 so emergency services can operate systems reliably.
7. Check state schedules and engage a certifier early: Confirm any state schedule variations that affect E2D requirements and seek early input from a registered building certifier or fire engineer for complex high-rise schemes.

Citations: NCC 2022 Volume One - Building Code of Australia (E2D4, E2D16-E2D21, S20C7, S21C7, S21C8, Specification 20, Specification 21, Specification 22); AS 1668.1; AS 1670.1; Specification 17 (sprinklers).