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
Fire dampers must have a fire resistance rating not less than the compartment wall or floor penetrated, be type-approved by SCDF and installed in accordance with SS 333. They must NOT be fitted in pressurising systems, smoke extract shafts, kitchen exhaust ducts or fume hood ducts.
CriticalClause 7.1.5Ventilation ducts must not pass through separating walls under any circumstance.
CriticalClause 7.1.2gExit staircases and smoke-free/fire lift lobbies must NOT be used as supply, exhaust or return air plenums for AHU systems.
CriticalClauses 7.1.8a, 7.1.9aSmoke detectors of approved type shall be incorporated in the return air stream of AHUs serving more than one storey/compartment, or any single AHU exceeding 15,000 m³/h, to shut down the AHU automatically on smoke detection.
CriticalClause 7.1.8cThe ventilation system for exit staircases shall be supply mode only at not less than 4 air changes per hour, with air intake directly from external space with intake point not less than 5 m from any exhaust discharge.
CriticalClause 7.1.9bSmoke-free lobby and fire lift lobby ventilation shall be supply mode only at not less than 10 air changes per hour, automatically activated by the building fire alarm system with remote manual override at FCC or main fire alarm panel.
CriticalClause 7.1.10Kitchen exhaust systems must be independent, discharge directly to external space at least 5 m from any air intake, and be cleaned and degreased at least once every 12 months by a specialist.
ImportantClauses 7.1.13a, 7.1.13d
Compliance thresholds
| Parameter | Value | Condition | Clause |
|---|---|---|---|
| Flexible connections at ends of ventilation ductwork | Maximum 4 m | Terminal units, extract units and ventilation grilles | Clause 7.1.2d(1) |
| Flexible joints (thermal movement) | Maximum 250 mm | Duct expansion joints | Clause 7.1.2d(2) |
| Control panel mounting height | 1.5 m to 1.8 m above FFL | Smoke control and smoke purging system control panels | Clause 7.1.2i(1) |
| Minimum clearance from fire hazards — smoke purging control panel | 1.5 m | Control panel for smoke purging systems in carparks | Clause 7.1.2i(2) |
| Air intake separation from exhaust discharge | Not less than 5 m | All air handling system intakes, pressurisation, smoke control | Clause 7.1.7a |
| Smoke detector requirement — single AHU | Exceeds 15,000 m³/h | Single AHU requiring return air smoke detector | Clause 7.1.8c(1) |
| Manual stop switch requirement — AHU | Exceeds 8,500 m³/h | AHU not centrally controlled | Clause 7.1.8d |
| Exit staircase ventilation rate | Not less than 4 air changes per hour | Supply mode mechanical ventilation for exit staircase | Clause 7.1.9b(4) |
| Smoke-free / fire lift lobby ventilation rate | Not less than 10 air changes per hour | Supply mode only ventilation for smoke-free or fire lift lobby | Clause 7.1.10a |
| Supply duct outside smoke-free/fire lift lobby — fire resistance rating | 1-hr fire resistance rating minimum | Supply duct running outside the lobby it serves | Clause 7.1.10c |
| Kitchen exhaust duct separation from unprotected openings | 3 m (reducible to 1.5 m on same plane) | KED running outside a building | Clause 7.1.13c(1) |
| KED separation from unprotected LPG cylinders | At least 3 m | Non-fire-rated kitchen exhaust duct | Clause 7.1.13c(4) |
| KED separation from LPG vapouriser or liquid-phase pipeline | At least 600 mm | Non-fire-rated kitchen exhaust duct | Clause 7.1.13c(4) |
| F&B outlet sharing exhaust — aggregate zone area | Maximum 2,000 m², max length 50 m | Restaurants/small F&B outlets sharing kitchen exhaust | Clause 7.1.13b(2)(a) |
| F&B outlet sharing exhaust — aggregate floor area | Maximum 1,000 m² | Restaurants and small F&B outlets sharing kitchen exhaust | Clause 7.1.13b(2)(b) |
| Flammable substances room — ventilation rate | 20 air changes per hour | Rooms involving use of flammable and explosive substances | Clause 7.1.14a(1) |
| Battery room — maximum hydrogen concentration | 1% of total room volume | Worst case simultaneous boost charging | Clause 7.1.15b |
| Battery room — mechanically ventilated minimum | 6 air changes per hour (or per BS EN IEC 62485, whichever higher) | Mechanically ventilated battery room | Clause 7.1.15e |
| Ducts through battery room compartments — fire resistance | 2-hr fire resistance rating | Essential ventilation ducts passing through other compartments | Clause 7.1.15f |
| Kitchen exhaust cleaning frequency | At least once every 12 months | All kitchen exhaust systems | Clause 7.1.13d(1) |
Interactive decision tree
Does your building have an air-conditioning or mechanical ventilation system?