Chapter 7
Mechanical Ventilation & Smoke Control Systems
Chapter 7 governs the design, installation and maintenance of air-conditioning, mechanical ventilation, pressurisation and smoke control systems in buildings to limit fire and smoke spread and to maintain tenable conditions for evacuation and firefighting. It sets out ductwork construction rules, fire damper requirements, special ventilation requirements for exits and protected spaces, pressurisation performance criteria, smoke extraction and purging system designs, and mandatory redundancy provisions for all critical life-safety ventilation systems.
Scope: All buildings (except PG I where explicitly exempted) that incorporate air-conditioning or mechanical ventilation systems, pressurised exit staircases or corridors, or engineered smoke control systems. Specific clauses apply to hotels, car parks, kitchens, battery rooms, and buildings with large or basement compartments.
Source: SCDF Code of Practice for Fire Precautions in Buildings 2023. This is a guidance summary — always verify against the full Fire Code clause text.
Critical points
An engineered smoke control system is required when any compartment floor area exceeds 5,000 m², total basement aggregate floor area exceeds 2,000 m² (subject to exemptions), or where atrium compartmentation is relaxed.
CriticalClause 7.4.1aThe building must be sprinkler-protected when an engineered smoke control system is installed.
CriticalClause 7.4.5bThe minimum clear smoke-free layer height shall be 2.5 m above floor level to maintain escape conditions.
CriticalClause 7.4.5eSmoke reservoirs for smoke removed from the room of origin must not exceed 2,000 m² (natural) or 2,600 m² (mechanical). For circulation/atrium spaces, limits are 1,000 m² (natural) and 1,300 m² (mechanical). Maximum reservoir length is 60 m.
CriticalClause 7.4.5fSmoke ventilation system must become fully operational within 60 seconds of activation.
CriticalClause 7.4.5pFans must be capable of operating at 250°C for 2 hours. Emergency standby fan (N+1) must be provided and auto-activates if duty fan fails.
CriticalClauses 7.4.5m, 7.5.1aSmoke purging system rate shall be at least 9 ACH. Jet fan car park system requires at least 12 ACH (or not less than 9 ACH if CFD fire modelling demonstrates acceptance criteria).
ImportantClauses 7.4.3b, 7.4.4g(1)
Compliance thresholds
| Parameter | Value | Condition | Clause |
|---|---|---|---|
| Compartment floor area triggering engineered smoke control | Exceeds 5,000 m² | Any compartment in a building or part thereof | Clause 7.4.1a(2) |
| Total basement aggregate floor area triggering engineered smoke control | Exceeds 2,000 m² | Total of all basement storeys (subject to exemptions) | Clause 7.4.1a(3) |
| Smoke vent aggregate effective opening | Not less than 2.5% of floor area served | Smoke vents required in basements | Clause 7.4.2a |
| Smoke purging rate | At least 9 ACH | Smoke purging system | Clause 7.4.3b |
| Smoke purging exhaust duct steel thickness | 1.2 mm (heavy gauge steel) | Exhaust ducts of smoke purging and jet fan systems | Clause 7.4.3g |
| Smoke purging exhaust fan operating temperature/duration | 250°C for 2 hours | Smoke purging exhaust fan | Clause 7.4.3h |
| Jet fan car park zone size | Not larger than 2,000 m² (excluding plant rooms and circulation) | Each smoke control zone in basement car park | Clause 7.4.4c(1) |
| Jet fan — minimum headroom | 3 m | Installation of jet fan system in car park | Clause 7.4.4d(4) |
| Car park exhaust rate (jet fan system) | At least 12 ACH (minimum 9 ACH with CFD modelling) | Car park during fire condition — jet fan system | Clause 7.4.4g(1) |
| Jet fan maximum inlet air speed (supply air) | 2 m/s | To prevent recirculation of smoke | Clause 7.4.4f(1) |
| Air velocity in escape routes (jet fan car park) | Not exceed 5 m/s | Escape routes and ramps in car park with jet fans | Clause 7.4.4f(2) |
| Car park jet fan supply/exhaust louver separation | At least 5 m apart | Supply and exhaust louvers, especially on same façade | Clause 7.4.4f(3) |
| Minimum smoke layer base height | 2.5 m above floor level | Design smoke layer base — engineered smoke control system | Clause 7.4.5e |
| Smoke reservoir — max area (room of origin, natural) | 2,000 m² | Natural smoke ventilation, smoke from room of origin | Clause 7.4.5f(2)(a) |
| Smoke reservoir — max area (room of origin, mechanical) | 2,600 m² | Mechanical smoke ventilation, smoke from room of origin | Clause 7.4.5f(2)(b) |
| Smoke reservoir — max area (circulation/atrium, natural) | 1,000 m² | Natural smoke ventilation, circulation or atrium space | Clause 7.4.5f(3)(a) |
| Smoke reservoir — max area (circulation/atrium, mechanical) | 1,300 m² | Mechanical smoke ventilation, circulation or atrium space | Clause 7.4.5f(3)(b) |
| Smoke reservoir maximum length | 60 m | Any smoke reservoir | Clause 7.4.5f(4) |
| Smoke ventilation system operational time from activation | Not exceeding 60 seconds | Any smoke ventilation zone | Clause 7.4.5p |
| Fan operating temperature/duration — engineered system | 250°C for 2 hours | All fans in engineered smoke control system | Clause 7.4.5m(2) |
| Maximum smoke mass flow | 175 kg/s | Smoke ventilation system practical limit | Clause 7.4.5h(1) |
| Minimum smoke layer temperature above ambient | 18°C above ambient | Smoke layer temperature for smoke ventilation system | Clause 7.4.5h(2) |
| Replacement air discharge velocity | Not exceeding 5 m/s | To prevent hindrance to escapees | Clause 7.4.5i(2) |
| Replacement air — discharge level below smoke layer | At least 1.5 m beneath smoke layer | Replacement air discharge to prevent fogging | Clause 7.4.5i(4) |
| Replacement air intake separation from exhaust | At least 5 m | Replacement air intake siting | Clause 7.4.5i(3) |
Interactive decision tree
Determine if smoke control provisions are required for this building.