a. An engineered smoke control system as specified in Cl.7.4.5 shall be provided where:
(1) the requirements for compartmentation specified in Cl.3.2.1, Cl.3.2.4a. and Cl.3.2.4b. are relaxed under the conditions in Cl.3.2.6 for Atrium spaces in a building, or
!
Note to QPs on Clause 7.4.1a.(1)
The QPs are required to consult SCDF to seek consent before making any plan submission. The consent that is given by SCDF to allow the use of engineered smoke control system in the proposal shall only relate to the relaxation on the compliance with the above requirements under Cl.3.2.1 and Cl.3.2.4a. and b. of the Fire Code.
(2) the total floor area of any compartment in a building or part of a building exceeds 5000m², or
(3) the total aggregate floor area of all basement storeys exceeds 2000m², except in any of the following situations:
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Explanations & Illustrations
Clause 7.4.1a.(1)&(2) : Provision
(2).tmb-firecode.png?Culture=en&sfvrsn=c199b00d_1 "Fg.7.4.1a(1)(2)")
Section
Figure 7.4.1a.(1) & (2) : Atrium smoke control system
Before the use of engineered smoke control system is allowed in any proposal, the SCDF shall be satisfied that the compartment height of atrium is connecting more than 3 storeys below the habitable height of 24m;
Where more than 3 storeys are interconnected and the size and volume is relaxed with provision of atrium smoke control system, only the first basement is allowed to form part of the upper storey.
A smoke control system shall be provided to any compartment in a building or part of a building which has a total floor area greater than 5000m². Smoke from any fire in such compartment would easily find its way into escape routes leading to exits or exit staircases. The activation of the smoke control system would ensure that the smoke layer would not be lower than 1.8m from floor level to allow occupants to find their ways to the exits or exit staircases.
(a) Where the basement or a portion of the basement is used as a car park, the car park shall comply with the requirements of Cl.7.4.3, provided it is compartmented from the rest of the basement.
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Explanations & Illustrations
Clause 7.4.1a.(3)(a) : Provision
(a).tmb-firecode.png?Culture=en&sfvrsn=1171b28_1 "Fg.7.4.1a(3)(a)")
Section
Figure 7.4.1a.(3)(a)
If the total floor area of basements 1 & 2 (other usage + car park) >2000m², engineered smoke control is required to be provided in the basement storeys; except the car parking areas in basement 1 & 2 which need to be provided with
smoke purging system under Cl.7.4.3.
Amendment History
| 7.4.1a.(3)(a) |
10 May 2019 |
Immediate |
Clarification |
Where the basement or a portion of the basement is used as a car park, the car park shall comply with the requirements of Cl.7.4.5, provided it is compartmented from the rest of the basement. |
10 May 2019 |
Download
|
(b) Where a plant/equipment room with floor area not exceeding 250m² is compartmented from rest of the basement, two doors remotely located from each other for better reach in firefighting operations shall be provided. The provision of a single door opening for this room is permitted provided the most remote part of the room is less than 8m from the door, and the equipment found inside this room, does not obstruct the throw of a water jet from a firefighting hose.
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Explanations & Illustrations
Clause 7.4.1a.(3)(b) : Provision
(b).tmb-firecode.png?Culture=en&sfvrsn=4d66dcd0_1 "Fg.7.4.1a(3)(b)")
Figure 7.4.1a.(3)(b)
Where the plant/equipment room is not greater than 250m², firefighters can fight a fire in that room from its doorway.
(c) Where a plant/equipment room with floor area exceeds 250m² but not 2000m², and for which smoke vents in accordance with Cl.7.4.2 or smoke purging system of at least 9 air changes per hour are provided.
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Explanations & Illustrations
Clause 7.4.1a.(3)(c) : Provision
(c).tmb-firecode.png?Culture=en&sfvrsn=a43a2bbf_1 "Fg.7.4.1a(3)(c)")
Figure 7.4.1a.(3)(c)
Where floor area of the plant/equipment room is in excess of 250m², but not exceeding 2000m², provision of smoke vents in accordance to Cl.7.4.2 or smoke purging system in accordance with Cl.7.4.3 would be acceptable.
Cl.7.4.1a.(3)(c) is meant to grant relaxation over the general requirement as service rooms are usually of low occupancy load. Common areas outside the plant rooms/service rooms shall be provided with engineered smoke control system.
(d) Where a service area comprising storerooms or workshops (restricted to staff only) which are compartmented, which are provided with smoke venting in accordance with Cl.7.4.2, or a smoke purging system of at least 9 air changes per hour in lieu of an engineered smoke control system. An automatic fire alarm/ extinguishing system in accordance with Table 6.4A shall be provided
where required.
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Explanations & Illustrations
Clause 7.4.1a.(3)(d) : Provision
(d)-1.tmb-firecode.png?Culture=en&sfvrsn=fc958457_1 "Fg.7.4.1a(3)(d)-1")
Figure 7.4.1a.(3)(d) - 1
The above clause is mainly applicable to hotel building. Service areas such as laundries, stores and workshops that are restricted to staff only shall be compartmented. The total area of these compartments shall not exceed 2000m² (per storey basis). Each compartment shall be provided with smoke venting or smoke purging system.
(d)-2.tmb-firecode.png?Culture=en&sfvrsn=a52496d6_1 "Fg.7.4.1a(3)(d)-2")
Figure 7.4.1a.(3)(d) - 2
a. Service areas in basement storey used as laundry area are areas that are normally occupied.
b. Hence, smoke dilution of at least 9 air charges may not suffice.
c. Adequate level of visibility and smoke dispersal shall be maintained for these areas to facilitate escape.
d. Engineered smoke control system shall be provided.
b. A smoke vent in accordance with Cl.7.4.2 shall be provided if the total aggregate floor area of all basement storeys
does not exceed 2000m². In lieu of smoke vents, a smoke purging system or an engineered smoke control system is permissible for car parks or other occupancies respectively.
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Explanations & Illustrations
Clause 7.4.1b. : Provision
Figure 7.4.1b. - 1
Figure 7.4.1b. - 2
Total aggregate floor area of basement storeys = Area of car park + staircases + services area (telecommunication room, transformer room etc.) + plant/equipment room of basement 1 + area of whole basement 2.
If total aggregate area< 2000m² (see Cl.7.4.2). If total aggregate area>2000m² (engineered smoke control system
or smoke purging is required), See also Cl.7.4.3 and Cl.7.4.1a.(3)(b) & (c)
7.4.2 Smoke vent
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Explanations & Illustrations
Clause 7.4.2 : Smoke vent
Figure 7.4.2 : Smoke vents for basement occupancies
a. Smoke ventilation shafts where extending through storeys above, shall be enclosed with imperforate walls having minimum 1-hr fire resistance.
b. Separate smoke ventilation shafts and outlets shall be provided for each basement storey.
c. Smoke venting outlets shall be so arranged that a through draught can be created.
d. Outlets covered by stalled boards, or approved type pavement lights shall be readily openable/breakable.
e. The positions of all smoke vent outlets and the basement level or areas they serve shall be suitably indicated on the external face of the building adjacent to such outlets.
Smoke vents shall be adequately distributed along the perimeter of the space served, and its outlets shall be easily accessible during firefighting and rescue operations. Smoke vents shall comply with the following requirements:
a. the number and their sizes shall be such that the aggregate effective vent openings shall not be less than 2.5% of the floor area served;
b. the vent outlets, if covered under normal conditions, shall be openable in case of fire;
c. the position of all vent outlets and the areas they serve shall be suitably indicated adjacent to such outlets;
d. where ducts are required to connect the vent to outlets, the ducts shall either be enclosed in structure or be constructed to give at least 1-hr fire resistance rating; and
e. separate ducts and vent outlets shall be provided for each storey.
7.4.3 Smoke purging system
Smoke purging system, where permitted under this Code in buildings, shall conform to all of the following requirements:
a. The smoke purging system shall be independent of any other system serving other parts of the building.
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Explanations & Illustrations
Clause 7.4.3a.-d. : Smoke purging system
Section
Figure 7.4.3a.-d. : Smoke purging system with ducted supply air intake
The reasons for locating the remote manual start/stop switch in the FCC or main fire alarm panel on 1st storey (where FCC is not available) are:
a. to allow firefighting personnel to shut down the supply air system temporarily in the event that smoke is being drawn into the lobby through the outdoor air intake; and
b. to allow firefighting personnel to activate the supply sir system should the fire alarm system fail to automatically activate the supply air system.
b. The purging system’s purge rate shall be at least 9 air changes per hour.
c. The purging system shall be activated automatically by the building fire alarm system. In addition, a remote manual start-stop switch shall be located at the FCC, or at main fire alarm panel on first storey (where there is no FCC in the building). Visual indication of the operation status of the smoke purging system shall also be provided with this remote control.
d. Supply air shall be drawn directly from the external space and its intake shall not be less than 5m from any exhaust discharge openings. Outlets for the supply air shall be adequately distributed over the area served.
e. Where there is natural ventilation for the area served based upon evenly distributed openings equal to not less than 2.5% of the floor area of a given storey, such natural ventilation can be considered a satisfactory substitute for the supply part of the smoke purging system.
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Explanations & Illustrations
Clause 7.4.3e.-h. : Smoke purging system
Section
Figure 7.4.3e.-h. : Smoke purging system with natural opening for supply air intake
Exhaust fans shall be rated at minimum 250°C. Supply air part of the smoke purging system is provided via opening to the external air. The openings provided for supply air shall not be less than 2.5% of the floor area of each basement storey. Ramp openings, voids over car parking areas are considered acceptable openings for fresh air supply.
Where a smoke purging system consists of a supply and exhaust , both of which shall be designed such that each can operate in two sections.
The capacity of each section shall be sufficient to provide half the air changes required. Each section of the smoke purging system shall so constructed that in the event of failure of one section (exhaust part or supply part), the other section shall continue to operate. This can prevent failure of the system caused by failure of one single fan.
The exhaust and supply parts shall be electrically interlocked so that failure of any section of the exhaust part shall automatically shut down the corresponding section of the supply part, which can prevent total failure of the smoke purging system caused by the failure of one single fan.
In the event that any exhaust fan fails to run or is shut down for maintenance, the corresponding supply fan should not run so as to prevent fresh air from being pumped into the basement. The interlocking arrangement will not apply if smoke purging system consists of only the exhaust part. However, the exhaust system shall also be designed into two section as per the above.
f. Replacement air shall be provided and if it is supplied by a separate mechanical system, such a system shall be connected to a secondary power supply.
g. Exhaust ducts shall be fabricated from heavy gauge steel of at least 1.2mm thickness.
h. The exhaust fan shall be capable of operating effectively at 250ºC for 2 hours and be connected to a secondary power supply.
7.4.4 Ductless jet fan system
Amendment History
| 7.4.4 |
|
Immediate |
Relocated from Appendix 17 of Fire Code 2013 |
|
--- |
-
|
a. General
This system can be used in lieu of a smoke purging system for conventional car parks where passenger cars/light weight vehicles are parked alongside each other with common driveways. It is not intended for mechanised car park systems or other forms of car parking systems.
b. Provision of sprinkler system
(1) The basement car park shall be sprinkler-protected in accordance with the SS CP 52.
(2) The arrangement of the sprinkler heads and the jet fans shall be such that, upon the operation of the jet fans, the effect on the spray pattern of the sprinklers is minimised.
c. Zoning of car park
(1) All car park spaces shall be divided into smoke control zones with each zone not larger than 2000m2 (excluding plant rooms and circulation spaces) for the purpose of smoke containment and quicker location of fire. A commissioning test will be carried out using hot smoke to demonstrate that smoke can be contained within each zone and channelled to the extract fans.
(2) Each smoke control zone shall have its own jet fan system (fresh air fans, exhaust air fans and jet fans) to purge smoke from the affected zone. The ducts shall be fabricated from heavy steel gauge steel of 1.2mm thickness. Alternatively, sharing of the fresh air and exhaust air fans is permitted provided the fans, wiring and control panel are protected with at least 1-hr fire resistance rating. The exhaust fan system shall also be designed to run in at least two parts, such that the total exhaust capacity does not fall below 100% of the required rate of extract for the zones affected in the event of failure of any one part. This requirement is also applicable for mechanised supply fan system, if it is used.
d. Jet fan system
(1) The jet fan system shall be activated by the sprinkler system serving the basement car park level and any other areas located within the same level. The activation of the jet fan system shall be confined to the smoke control zone on fire and all its adjacent zones. A firefighter cut-off and activation (override) switch shall be provided at the FCC. As an alternative form of fan activation, the use of smoke detectors to activate the jet fan system is allowed, provided:
(a) the detectors are positioned at the effective mid-range of the jet fan profile;
(b) in-duct smoke detector is located at the start point of the exhaust duct; and
(c) jet fan system shall only operate upon activation of two smoke detectors. This is to minimise false alarms.
(2) The jet fan system shall be provided with a secondary source of power supply through automatic operation of an emergency generator in case of failure of the primary power supply source.
(3) The jet fans shall be distributed at a spacing of 2⁄3 of the tested effective range of each jet fan. The tested effective range of the jet fan shall be taken as the distance up to the point at 0.2m/s of the air-velocity distribution profile.
(4) The minimum headroom for the installation of the jet fan system is 3m.
(5) The interaction of the various components of the jet fan system shall be as follows:
(a) Each group of exhaust fans for each smoke control zone shall be interlocked with its corresponding groups of jet fans for that zone.
(b) If the group of exhaust fans stops/fails in any smoke control zone, the corresponding group of jet fans in that zone shall stop. But if any of the exhaust fans is still in operation in a particular smoke control zone, all the jet fans in that zone shall continue to operate.
(c) The exhaust fan shall continue to run even if any corresponding group of jet fans fails.
(d) The other groups of jet fans shall continue to run even if any one group of jet fans fails.
(e) If the fire alarm signal is isolated, the exhaust fans and jet fans shall continue to run at high speed. If the fans are manually restarted, both the exhaust fans and jet fans shall continue to run at high speed until they are set to low speed at the field control panel.
(6) The jet fan system shall be independent of any systems serving other parts of the building.
(7) The jet fan system design shall be such that the bulk air velocity induced by the jet fans is sufficient to stop the advance of the ceiling jet within 5m from the fire location in the direction opposite to the induced bulk air flow.
(8) The smoke control sub-panel in each smoke control zone is to be connected to the main smoke control panel, such that any isolation of jet fan system at a particular zone is automatically displayed at the main smoke control panel.
(9) The car park main smoke control panel at the FCC/Guard house and remote local panel for the supply and exhaust fans shall indicate, by means of indicator lights, whether the fans are on low or high speed. The panels are also required to have the individual group of jet fans indication lights interlocked with the main exhaust fans in the respective smoke control zones.
(10) In the event of failure of the primary source of power supply and subsequent operation of the secondary power supply, the mode of operation of the jet fan system during the fire mode shall follow that prior to the failure of the primary power supply. For example, if the operation of jet fan system in a particular smoke control zone is switched off by the firefighter during fire mode condition and the primary source of power fails, the subsequent operation of the secondary power supply shall be such that the jet fan system remains in the previous fire mode condition, i.e. non-operational mode for that smoke control zone, while the other smoke control zones resume operation.
(11) The jet fan system design shall take into consideration the presence of any down-stand beams and other obstructions that are of depths of more than 1/10 of the car park floor to ceiling height so as to account for any resistance to airflow.
(12) On activation of the jet fan system, the movement of smoke towards the extraction point(s) shall not adversely affect the means of escape and cause smoke to be blown into the lobby area or exit staircases.
(13) The operation of the jet fan system should be such that there are no stagnant areas where smoke can accumulate in the event of fire.
(14) The operation of the jet fan system shall not cause the volume of air movement to be greater than that volume extracted by the main exhaust fans.
(15) There shall be at least one viable approach route (i.e. where acceptance criteria for firefighters are in accordance with Cl.7.4.4g. and Diagram 7.4.4e.(4)-2) for the firefighters to any possible fire location up to a distance of 5m from that fire. As such, information as to the viable approach route shall be displayed at the main fire alarm panel. This can be achieved by arranging the sprinkler control zone to correspond with that of the smoke control zone. Upon detection of the fire within a particular smoke control zone / sprinkler zone, reference can be made to the display showing the viable approach route for that particular smoke control zone.
Amendment History
| 7.4.4d.(15) |
1 Mar 2021 |
1 Mar 2021 |
Reinstatement of past requirement |
Nil |
1 Mar 2021 |
Download
|
e. Wiring arrangement of jet fans
(1) All jet fans shall be connected to the local jet fan control panel in groups of not more than three jet fans.
(2) Each group will be connected by fire-rated cabling.
(3) Each group of jet fans will be protected by a separate MCB (main circuit breaker), with power supply compliant with SS CP 5, to prevent the failure of all the jet fans at once due to tripping of the main RCB, e.g. due to overloading.
(4) The jet fans shall also be wired in a zigzag configuration and no two consecutive jet fans in a straight line are to be wired in the same group. In the event of failure of one group of jet fans, the next corresponding group will be able to drive the
smoke towards the exhaust location to be extracted (see Diagram 7.4.4e.(4) - 1 &
2). Should one group of jet fans fail, all other groups shall still continue
to run.
(5) The location of the local control panel for the operation of the jet fans within each zone shall be in a relatively safe area within the zone and be spaced as least 5m apart from the local control panels of adjacent zones. This is to minimise the
risk of a fire affecting all the control panels if they be spaced closely together, and thus rendering the ineffectiveness of the jet fan system.
f. Provision of supply air
(1) Supply air to the car park can be provided via mechanised supply air fans or by permanent openings of at least 2.5% of the floor area. Whichever is used, the maximum inlet air speed should be 2m/s to prevent recirculation of smoke.
(2) The air velocity within escape routes and ramps shall not exceed 5m/s to prevent escapees from being hindered by the air flow.
(3) The replacement air intakes shall face away from any smoke exhaust points and be sited at least 5m apart so as to prevent recirculation of smoke. If the supply and exhaust louvers are located on the same façade of the building, they shall also
be sited at least 5m apart.
(4) The replacement air intake shall be located on the opposing end of the smoke exhaust points so that there is no opposing flow between the supply air and the smoke that is drawn towards the exhaust fan.
g. Exhaust fan design
(1) The car park shall be provided with at least 12 air changes per hour during a fire. A lower air change not less than 9 air changes can be permitted provided the acceptance criteria stipulated in the Cl.7.4.4g.(1)(b) can be achieved through
fire modelling:
(a) Hot smoke test / CFD fire modelling
The effectiveness of the jet fans system design shall be demonstrated using hot smoke test in accordance with Cl.7.4.4j.. The heat release rate of the fuel load for the hot smoke test shall be
at least 1MW. The relevant PE or Fire Safety Engineer should decide on the fire location(s) that is (are) deemed most onerous with justification. In addition to the hot smoke test, Computational Fluid Dynamics (CFD) fire modelling will also be required
in the following instances:
(i) If air change per hour is smaller than 12.
(ii) If there are general goods vehicle or coaches where design fire size exceeds 4 MW (i.e. car fire).
(iii) If replacement air is a combination of natural and mechanical means.
(iv) If spacing of jet fans is more than 2/3 of the tested effective range.
The CFD study is to be endorsed by a Fire Safety Engineer (FSE) to verify the conformance of the jet fans system with the acceptance criteria as
stipulated in Cl.7.4.4g.(1)(b). The FSE is also required to put up a fire engineering report. Some of the accepted fire modelling software includes FDS, Swift-AVL, Fluent and Pheonics.
(b) Acceptance criteria
(i) Not more than 1000m2 of the car park space can be smoke-logged for at least 20 mins, regardless of whether the fire is located within the smoke control zone or across the zone boundaries (Note: After the 20 mins duration,
smoke is expected to remain confined within the 1000m2 area). Within this smoke-logged area, there shall be at least 1 viable route for the firefighters where the following conditions are satisfied:
* Smoke temperature
shall not exceed 250oC at a height of 1.7m from floor level.
* Visibility shall not be less than 5m at a height of 1.7m from floor level.
These conditions shall commence at a distance of 5m from the fire
location in the direction opposite to the induced bulk air flow induced by the jet fans. All other areas outside the smoke-logged area shall be kept substantially free from smoke i.e. smoke temperature not more than 60oC and visibility
of at least 25m (Diagrams 7.4.4e (4) - 1 & 2).
(Note: If hot smoke test is performed, assessment is to be made on the operation of the jet fans system, movement of smoke towards the extraction points and smoke spread.
The latter 2 aspects can be generally verified using the above visibility criterion. The temperature criterion need not be verified in view of the nature of the hot smoke test.)
(c) CFD fire modelling input parameters
(i) Fire Size
The design fire size shall be based on at least 4MW steady-state fire (i.e. car fire). For general goods vehicle, the design fire size shall be based on at least 10MW steady state fire (FSE is expected to provide justification
for the bigger fire size other than the car fire).
(ii) Type of fire
The type of fire shall be flaming polyurethane.
(iii) Location of fire
Generally, the fire should be located furthest away from the exhaust points and in between zones. The relevant PE or Fire Safety Engineer should decide on the
fire location(s) that is (are) deemed most onerous with justification.
(iv) Down-stand beams and other obstruction
The CFD model shall take into consideration the presence of any down-stand beams and other obstruction that are
of depths of more than 1/10 of the car park floor to ceiling height so as to account for any resistance to airflow and turbulence.
(v) Jet fan velocity profile
Validation model of the velocity profile is to be carried
out for a single jet fan. The data from the model shall be compared against physical test data.
As such, the jet fan shall be tested for velocity profile by an accredited testing laboratory for comparison with the simulated velocity
profile. The test report is to be attached to the Fire Engineering Report. The equation to be used for the deviation between the CFD profile and actual test profile is as follows:
Equation : Deviation = [(A-B) / B] X 100%
Where
:
A = distance/width/height from CFD profile
B = distance/width/height from actual test profile
The deviation of the distance, width and height of the actual profile from the simulated profile at the various air velocities
should be within 10%.
(vi) Duration of fire simulation
The duration of the fire simulation shall be at least 20 mins.
(vii) Sprinkler activation
The model shall assume there is no sprinkler activation for the design fire size specified in Cl.7.4.4g.(1)(c)(i).
(viii) Grid resolution
The grid size to be used in the fire model shall not be larger than 200mm X 200mm X 200mm in the smoke control zone where fire is located and its adjacent zones. Other than these zones, the grid size
shall not be larger than 400mm X 400mm X 400mm. Alternatively, the relevant PE or FSE undertakes a grid resolution study to ascertain the appropriate grid size needed for the fire size and smoke flows modelled (e.g. outcome of study showing that additional
resolution does not make much of a difference to the results).
(ix) Sensitivity study
A sensitivity study is to be carried out to show the impact of 1 group of jet fan failure nearest the fire on the overall effectiveness
of the jet fans system. This study is applicable to both fire modelling and hot smoke test. Notwithstanding the failure of 1 group of jet fans, the acceptance criteria must still be maintained.
(2) The capacity of the exhaust fan and any associated ducting shall be calculated on the basis that the pressure in the car park close to the extract points is equal to the external atmospheric pressure.
(3) Each smoke control zone of the car park shall have its own exhaust fan system. The exhaust fan system in each zone should be designed to run in at least two parts, such that the total exhaust capacity does not fall below 50% of the required rate of
extract in the event of failure of any one part, and that a fault or failure of the exhaust fan system in one zone will not affect the operation of the exhaust fan system in the other zones. The above requirement is also applicable for mechanised
supply fan systems, where used. (Note: If there is sharing of the exhaust air fans, see Cl.7.4.4c.(2))
(4) The smoke discharge points shall be located such that the smoke extracted from the smoke exhaust fans does not affect any occupied area or means of escape at the level where smoke is discharged.
h. Fire resistance of jet fan system
The jet fan system, such as the mechanised air supply fans, smoke exhaust fans, jet fans, duct works and wiring shall be capable of operating effectively at 250°C for 2 hours. The fans, ducts and wiring shall be tested in accordance with BS 7346:
Pt 2, BS 476: Pt 24 and SS 299 respectively.
Amendment History
| 7.4.4g.(1) |
1 Mar 2021 |
1 Mar 2021 |
Reinstatement of past requirement |
Exhaust fan design (1) The car park shall be provided with at least 12 air changes per hour during a fire. (2) ……………….. |
1 Mar 2021 |
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|
i. Operations and maintenance manual
An operations and maintenance manual shall be attached. The manual shall contain the roles and responsibilities of the building owner/operator, the restrictions placed on the building, identification of the sub-systems, servicing and maintenance plan, fault identification, etc. The manual can also be used as a guide for future renovations and changes to the building.
Amendment History
| 7.4.4i |
1 Mar 2021 |
1 Mar 2021 |
Reinstatement of past requirement |
Nil |
1 Mar 2021 |
Download
|
j. Commissioning test
The Registered Inspector who carries out commissioning test of the jet fans system may make reference to Table 2 of BS 7346 - Part 7 as a guide. When hot smoke test is performed, the PE/FSE shall use a test fire size of 1MW. Reference may be made to AS 4391 on hot smoke test and PE is advised to make reference on how the test can be prepared and carried out in a proper manner.
Amendment History
| 7.4.4j |
1 Mar 2021 |
1 Mar 2021 |
Reinstatement of past requirement |
Nil |
1 Mar 2021 |
Download
|
7.4.5 Engineered smoke control system
a. Acceptable design guidance
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Explanations & Illustrations
Clause 7.4.5a. : Engineered smoke control system
( No illustration )
BR 186 and BR 258 and subsequent revisions / amendments have been adopted as acceptable design guides for engineering smoke control systems. Other acceptable standards such as NFPA 92A may be adopted, taking into consideration that the basic requirements of smoke control system in the Fire Code should be strictly complied with. In the case of differences in requirement between BR 186 / 258 and NFPA 92A, e.g. classification of fire size, the clear height of smoke layer base, the QPs should consult the SCDF to determine which requirement to adopt before building plan submission. Other acceptable standards referred to from time to time will be evaluated and QPs will be informed through SCDF’s circulars.
The engineered smoke control system shall be in the form of a smoke ventilation system by natural or mechanical extraction designed in accordance with BR 186, BR 258, BR 368 and other acceptable standards:
b. Sprinkler system
R
Rationale - Clause 7.4.5b
The main reason that sprinkler system must be provided is to control the fire size. The sprinkler head spacing in respect of both hazard and classification determines the size of a fire, in area and perimeter. The activation of sprinkler heads would, besides controlling the fire size, help to reduce the build-up of heat and toxic gases, which can lead to flashover and smoke explosions. Based on research, if the fire is not sprinkler controlled, the fire size would be unlimited and therefore, fire size could not be established.
A building provided with an engineered smoke control system shall be sprinkler-protected.
c. Fire size
(1) Non-industrial buildings
The capacity of the engineered smoke control system shall be calculated based on the incidence of a likely maximum fire size for a sprinkler controlled fire as recommended in the following table:
| TABLE 7.4.5c.(1) : FIRE SIZE FOR NON- INDUSTRIAL BUILDINGS |
|---|
| Occupancy (Sprinkler-protected) | Fire Size |
|---|
| Heat Output (MW) | Perimeter of Fire (m) |
|---|
| Shops | 5 | 12 |
| Shops (fast response sprinklers) | 2.5 | 9 |
| Offices | 1 | 14 |
| Hotel Guest Room | 0.5 | 6 |
| Hotel Piublic Areas | 2.5 | 12 |
| Assembly Occupancy with Fixed Seating | 2.5 | 12 |
Amendment History
| Table 7.4.5C.(1) |
15 Sep 2020 |
15 Sep 2020 |
Clarification |
Existing Table 7.4.5C.(1) |
15 Sep 2020 |
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|
(2) Industrial buildings
The requirements for design fire size are applicable to sprinkler- protected industrial premises (factory and warehouse) without in-rack sprinklers and limited to the design of smoke control system based on Cl.7.4.
(a) Fire growth
The fire growth can be evaluated by the following generic fire growth curve (also referred to as ‘t2 fire’), that represents the general types of combustible material present within an enclosure:
Qmax = ∝ (t-ti)2 ------------------------------------- equation (1)
where:
Qmax = heat release rate (kW);
∝ = fire growth parameter (kJ/s3);
t = time (s);
ti = time
of ignition (s) (taken here as zero)
The fire growth parameter varies with the fire load density and the fire load configuration factor. However, for purpose of design, fire growth parameter can be generally defined as follows:
| TABLE 7.4.5c.(2)(A) : FIRE GROWTH PARAMETER FOR INDUSTRIAL BUILDINGS |
| Fire growth rate |
Fire growth parameter (kJ/s3) |
Time for Qg = 1MW (s) |
| Slow |
0.0029 |
600 |
| Medium |
0.012 |
300 |
| Fast |
0.047 |
150 |
| Ultra fast |
0.188 |
75 |
|
Note:
The fire growth rate that is applicable through available literature or standard such as the SFPE Handbook shall be adopted. In the instance where the fire growth rate lies in between the range as stated above, the more conservative fire
growth rate is to be used.
|
(b) Design fire – sprinkler-protected
(i) The heat output of the design fire is assumed to increase according to equation (1) until sprinkler operation is deemed to occur at time t8. Following sprinkler operation, the heat output of the fire is considered to remain constant.
(ii) The capacity of the smoke control system shall be based on the fire size that is controlled by activation of 2nd ring of sprinklers.
(iii) The operation of the sprinkler system at ts and the corresponding fire size can be determined by hand calculations based on fire engineering principles or the use of fire engineering tools such as FPETool from National Institute of Standards and
Technology (NIST). Whichever approach is used, the following design factors governing its calculation are as follows:
• Rate of fire growth
The type of fuel load and its configuration in the premises shall govern the rate of fire growth which can be represented using equation (1) and Table 7.4.5c.(2)(a).
• Sprinkler response time index (RTI)
The RTI is the thermal sensitivity of the sprinkler and shall be based on the manufacturer’s specification.
Example:
Standard response sprinkler – 105m0.5s0.5;
Fast response sprinkler - 50m 0.5s0.5;
ESFR - 26m0.5s0.5
• Temperature rating of sprinkler
The operating temperature of the sprinklers shall be based on SS CP 52 (e.g. 141°C or 68°C).
• Ambient temperature
Room temperature for air-conditioned spaces and non-air conditioned spaces can be taken as 25°C and 30°C respectively.
• Ceiling height
The ceiling height shall be based on the height, measured from the finished floor level to the soffit of the ceiling/roof.
• Spacing of sprinkler above fire
Sprinkler spacing shall be based on SS CP 52 (e.g. 3m by 3m or 4m x 3m).
Note: The application of FPETool from NIST or any other software in determining the activation time of the sprinkler system and the corresponding fire size has its limitations. Some of the software programs are based on Alpert’s correlations where
a number of fundamental assumptions are made such as flat smooth ceilings, unconfined smoke flow, axisymmetric plumes (not near walls or corners), location of detector close to the ceiling, etc.. Such assumptions shall thus be taken into consideration
when using this tool.
(iv) The capacity of the smoke control system shall also take into consideration the possibility of forklift or general goods vehicle on fire along the internal ramps/driveways. For design purposes, the design fire size shall be taken as follows:
| TABLE 7.4.5c.(2)(b)(iv) : VEHICLE DESIGN FIRE SIZE |
| Type of vehicle |
Design fire size |
| Forklift or car |
4MW |
| General goods vehicle |
10MW |
(c) Determination of perimeter of fire
(i) Fire perimeter for forklift/car and goods vehicle
The fire perimeter is used to determine the mass flow rate of smoke. For forklift or general goods vehicle, the perimeter of fire shall be taken as follows:
TABLE 7.4.5C.(2)(C)(I) : FIRE PERIMETER SIZE Type of vehicle Perimeter of fire Forklift or car 5m x 2m General goods vehicle 9m x 2.5m
| TABLE 7.4.5c.(2)(C)(I) : FIRE PERIMETER SIZE |
| Type of vehicle |
Perimeter of fire |
| Forklift or car |
5m x 2m |
| General goods vehicle |
9m x 2.5m |
(ii) Fire perimeter other than for forklift/car and general goods vehicle
Other than for forklift/car and general goods vehicle, the following equation is used to calculate the fire perimeter for a square fire of equal sides:
P = 4(Qc/Qr)0.5 -------------------------------- equation (2)
where:
P = fire perimeter (m);
Qc = convective heat output = 0.7Qmax (kW);
Qr = heat release rate per unit
area (kW/m2), see Table 7.4.5c.(2)(c)(ii)
Where elongated storage configurations such as racking or shelving are used, the fire perimeter is determined using the following equation:
P = 2[Qc/(Qr x d)] --------------------------- equation (3)
where:
Qc = convective heat output = 0.7Qmax (kW);
Qr = heat release rate per unit area (kW/m2), see Table 7.4.5c.(2)(c)(ii)
d = depth of rack (m)
For purpose of calculating the fire perimeter, the values for Qr given in Table 7.4.5c.(2)(c)(ii) are used.
| TABLE 7.4.5c.(2)(C)(II) : HEAT RELEASE RATE |
| Building Use |
Heat release rate per unit area, Qr (kW/m2) |
| Industrial |
260 |
| Storage |
500 |
Amendment History
| 7.4.5c.(2) |
|
Immediate |
Relocated from Appendix 18 of Fire Code 2013 |
|
--- |
-
|
d. Capacity
E
Explanations & Illustrations
Clause 7.4.5d. : Engineered smoke control system
Section
Figure 7.4.5d. - 1 : Scenario A
Section
Figure 7.4.5d. - 2 : Scenario B
Section
Figure 7.4.5d. - 3 : Scenario C
The engineered smoke control system can be designed based on smoke control zones, provided the system is capable of handling the largest demand of smoke produced under the worst case scenario. The worst scenario would be scenario C where the fire size occurring at 1st storey as shown in the figure above. As the smoke and hot gases rise through the upper levels, a very large quantity of smoke would be further generated through entrainment and greater cooling effect of smoke would occur.
The capacity of an engineered smoke control system shall be capable of handling the demand for smoke exhaust in a worst case scenario.
e. Clear layer
E
Explanations & Illustrations
Clause 7.4.5e. : Engineered smoke control system
Section
Figure 7.4.5e.
The clear height below smoke layer (Y) = 2.5m minimum.
The main purpose is to permit occupants to evacuate in a clear breathable layer. The maintenance of this clear layer will aid the firefighting operations. The lowest cceptable temperature of smoke layer to prevent loss of buoyancy is 20°C above ambient, i.e. 35°C (or 308K).
The highest temperature to prevent a radiation risk to people passing beneath the smoke layer should not exceed 200°C (or 473K). This temperature may appear high for areas such as means of escape, but it is considered acceptable.
The design smoke layer base shall be above the heads of people escaping beneath it. The minimum height shall be 2.5m.
(1) Smoke reservoirs to prevent the lateral spread of smoke, and to collect smoke for removal, shall be of non-combustible construction capable of withstanding smoke temperatures.
E
Explanations & Illustrations
Clause 7.4.5f.(1) : Engineered smoke control system
.tmb-firecode.png?Culture=en&sfvrsn=7f34e2a_1 "Fg.7.4.5f(1)")
Section
Figure 7.4.5f.(1)
Smoke reservoirs could be formed by using either the building’s geometry or by using smoke curtains/shutters/non-combustible downstands, such as fire resisting boards, glazing. The screens, which extend downwards from the roof or ceiling to form the smoke reservoir, should preferable be smoke tight. They should be resistant to the effects of the fire. The main reasons for restricting lateral spread of smoke by providing smoke reservoir are:
a. to prevent damage or even ignition to combustible parts of ceiling lining or service components if hot smoke layers are allowed to spread uncontrolled over unlimited areas; and
b. to prevent smoke layer (because of mixing with cold air in the course of lateral travel) become relatively cool and shallow. This will result in roof vents being unable to expel the smoke efficiently. Smoke vents would be most effective if the temperature of the smoke layer is high and that the layer beneath the vent is quite deep, thus developing a reasonable pressure differential to act to expel the smoke through the vent.
(2) For cases where smoke is removed from the room of origin, the smoke reservoir size for a smoke ventilation system shall not exceed:
E
Explanations & Illustrations
Clause 7.4.5f.(2) : Engineered smoke control system
.tmb-firecode.png?Culture=en&sfvrsn=cdc02197_1 "Fg.7.4.5f(2)")
Section
Figure 7.4.5f.(2)
Room of origin includes atria, large shopping floor, rooms or spaces. Large reservoir will present a large surface area to the smoke layer, which can lead to considerable heat losses from it. Smoke control system is therefore designed with maximum specified smoke reservoir size to prevent excessive heat loss from the smoke layer, which leads to loss of its buoyancy for effective smoke venting or exhaust from the building.
(a) 2000m² for a natural smoke ventilation system; and
(b) 2600m² for a mechanical smoke ventilation system.
(3) For cases where smoke is removed from a circulation space or atrium space, the smoke reservoir size for a smoke ventilation system shall not exceed:
E
Explanations & Illustrations
Clause 7.4.5f.(3) : Engineered smoke control system
-1.tmb-firecode.png?Culture=en&sfvrsn=4d868cf6_1 "Fg.7.4.5f(3)-1")
Section
Figure 7.4.5f.(3) - 1 : Smoke extraction from atrium circulation space
-2.tmb-firecode.png?Culture=en&sfvrsn=df98c57a_1 "Fg.7.4.5f(3)-2")
Figure 7.4.5f.(3) - 2
-3.tmb-firecode.png?Culture=en&sfvrsn=dd4ca788_1 "Fg.7.4.5f(3)-3")
Elevation A
Figure 7.4.5f.(3) - 3
For cases where smoke is allowed to spill into the circulation or atrium space before extraction takes place, the smoke reservoir sizes are halved. Individual smoke reservoir can be created for circulation or atrium space, subject to 1300m² for mechanical ventilation or 1000m² for natural ventilation.
The smoke reservoirs could be formed by using either the building’s geometry or by using smoke curtains/shutters/non-combustible downstands.
The depth of any screen used for subdivision shall be taken into account. Screens should terminate at a minimum of 500mm below the smoke layer base.
The main reasons for limiting the size of reservoirs are:
a. smoke from a fire leaves a workshop and enters the smoke reservoir in the circulation or atrium space, it will encounter turbulence and greater mixing occurs which produces more smoke; and
b. the movement of smoke from workshop into the circulation or atrium space would cause the smoke to lose heat to the surrounding structure through conduction and further loss occurring due to downward radiation. This movement would cause the smoke to lose some of its buoyancy.
For factory, the circulation or atrium space serves as a means of escape for people escaping from the workshop, before exiting to a safe area outside the building. The circulation or atrium space is therefore an additional stage to the escape route, which requires to be protected from the effects of fire and smoke.
For warehouse, which is primarily designed for storage, the smoke ventilation system provided would be for the purpose of heat and smoke release from the building. Warehouse should be treated differently from factory.
For warehouse, which is used for palletised storage, consideration should be given to the possible collapse of stacks or radiated heat spreading the fire to adjacent stacks. In tall warehouse, which is used for high rack storage, the smoke layer temperature may not go beyond 35°C and therefore, the smoke layer could well go below the level of the storage. Consideration should be given to the existence of ceiling jet occurring in the smoke layer.
(a) 1000m² for a natural smoke ventilation system; and
(b) 1300m² for a mechanical smoke ventilation system.
(4) Reservoir length
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Explanations & Illustrations
Clause 7.4.5f.(4) : Engineered smoke control system
-1.tmb-firecode.png?Culture=en&sfvrsn=32aa87c0_1 "Fg.7.4.5f(4)-1")
Figure 7.4.5f.(4) - 1 : Rectangle-shaped smoke reservoir
-2.tmb-firecode.png?Culture=en&sfvrsn=8c92abea_1 "Fg.7.4.5f(4)-2")
Figure 7.4.5f.(4) - 2 : Oval-shaped smoke reservoir
-3.tmb-firecode.png?Culture=en&sfvrsn=5e36c80a_1 "Fg.7.4.5f(4)-3")
Figure 7.4.5f.(4) - 3 : Square-shaped smoke reservoir
-4.tmb-firecode.png?Culture=en&sfvrsn=24672526_1 "Fg.7.4.5f(4)-4")
Figure 7.4.5f.(4) - 4 : Circle-shaped smoke reservoir
-5.tmb-firecode.png?Culture=en&sfvrsn=f3a702de_1 "Fg.7.4.5f(4)-5")
Figure 7.4.5f.(4) - 5 : Rhombus-shaped smoke reservoir
Smoke reservoirs can be formed of different shapes. In order to prevent smoke from excessive heat loss, the length of an individual smoke reservoir within a mall, factory or warehouse spaces shall not exceed 60m.
The maximum length of the smoke reservoir shall not exceed 60m.
(5) Stagnant regions
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Explanations & Illustrations
Clause 7.4.5f.(5) : Engineered smoke control system
-1.tmb-firecode.png?Culture=en&sfvrsn=cc6f0436_1 "Fg.7.4.5f(5)-1")
Section
Figure 7.4.5f.(5) - 1
A stagnant region occurred in a long smoke reservoir when venting or extraction is not properly distributed or when circulation/atrium or mall has a closed end.
-2.tmb-firecode.png?Culture=en&sfvrsn=6a707273_1 "Fg.7.4.5f(5)-2")
Section
Figure 7.4.5f.(5) - 2
A stagnant region could also be formed by physical obstruction in the smoke reservoir e.g. Beam. If a smoke layer is stagnant, it will cool down and will mix into the air below. If the air space under a smoke layer is stagnant, it will tend to fill up with hazy smoke of sufficient density to affect visibility. Venting or extraction should be well distributed in the smoke layer or smoke reservoir. The air inlets at low level should also be well distributed so that the air, which is being drawn in will purge as much of the low-level clear air as possible.
Adequate arrangement(s) shall be made in each smoke reservoir for the removal of smoke in a way that will prevent the formation of stagnant regions.
(6) Perforated ceiling
E
Explanations & Illustrations
Clause 7.4.5f.(6) : Engineered smoke control system
.tmb-firecode.png?Culture=en&sfvrsn=d8dd4f6d_1 "Fg.7.4.5f(6)")
Section
Figure 7.4.5f.(6)
If the smoke reservoir incorporates a false ceiling, then the space above the false ceiling may be included in the depth of the smoke reservoir provided the screens forming the reservoir extend up to the structural ceiling, the perforations in the false ceiling are at least 25% of the total area of the reservoir, and the space occupied by services etc. above the ceiling is not greater than 50% of the volume above the ceiling.
For cases where the smoke reservoir is above the false ceiling, the ceiling shall be of perforated type with at least 25% opening.
g. Discharge of smoke
(1) Removal of smoke
For cases where smoke is removed from a circulation space or atrium space, the rooms discharging smoke into the circulation space/atrium spaces shall either:
Amendment History
| 7.4.5g |
15 Sep 2020 |
15 Sep 2020 |
Clarification |
Discharge of smoke For cases where smoke is removed from circulation space or atrium space, the rooms discharging smoke into the circulation space/atrium spaces shall either: (1) have a floor area of not exceeding 1000m² (for natural ventilation system) or 1300m² (for mechanical ventilation system), or (2) be subdivided such that smoke is vented to the circulation space or atrium only from part of the room with floor area not exceeding 1000m² (for natural ventilation system) or 1300m² (for mechanical ventilation system), that is adjacent to the circulation space or atrium. However, the remainder of the room needs to be provided with an independent smoke ventilation system(s). |
15 Sep 2020 |
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(a) have a floor area of not exceeding 1000m² (for natural ventilation system) or 1300m² (for mechanical ventilation system), or
E
Explanations & Illustrations
Clause 7.4.5g.(1) : Engineered smoke control system
-1.tmb-firecode.png?Culture=en&sfvrsn=5a4d498b_1 "Fg.7.4.5g(1)-1")
Figure 7.4.5g.(1) - 1
The main purpose of controlling the max. floor area is to limit the distance to the circulation or atrium space as smoke and hot gases would tend to cool and lose its buoyancy if floor area becomes larger.
Where the workshop units are not larger than 1000m² (natural ventilation in the circulation or atrium space) or 1300m² (with powered extraction in the circulation or atrium space), smoke from these units are allowed to discharge into the circulation or atrium space. If the units are larger than the sizes mentioned above, the smoke layer from a fire in any of these units would lose temperature to a great extent thereby losing its buoyancy as it would be controlled by sprinklers located within the units. In addition, the smoke layer would also lose some heat to the building structures. Thus, the venting of smoke layer into the circulation or atrium space becomes not effective, as cooling of smoke takes place leading to dispersal of smoke and smoke logging.
-2.tmb-firecode.png?Culture=en&sfvrsn=450e8dbc_1 "Fg.7.4.5g(1)-2")
Figure 7.4.5g.(1) - 2
The combined floor area of multiple shops should not exceed 1000m2 or 1300m2 (power extraction) fronting circulation or atrium space. It is acceptable to use screen to channel the smoke from the shop into the circulation or atrium space, subject to maximum 14m separation between channel screens.
(b) be subdivided such that smoke is vented to the circulation space or atrium only from part of the room with floor area not exceeding 1000m² (for natural ventilation system) or 1300m² (for mechanical ventilation system), that is adjacent to the circulation space or atrium. However, the remainder of the room needs to be provided with an independent smoke ventilation system(s).
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Explanations & Illustrations
Clause 7.4.5g.(2) : Engineered smoke control system
.tmb-firecode.png?Culture=en&sfvrsn=408e7a1d_1 "Fg.7.4.5g(2)")
Figure 7.4.5g.(2)
Where a large workshop is extracted separately from the circulation/atrium space, it can have ceiling reservoirs up to twice the area permitted in the circulation/atrium space; 2000m² (natural ventilation system) or 2600m² (mechanical ventilation system) as no smoke is allowed to spill into the circulation/atrium space.
(2) Exhaust points
The minimum number and siting of exhaust points within a smoke reservoir shall be determined to prevent “plug-holing” effect at the exhaust points. The exhaust point shall comply with the following plugholing equation.
h. Limitations
E
Explanations & Illustrations
Clause 7.4.5h. : Engineered smoke control system
( No Illustration )
1. It has commonly been found that very large exhaust rates, typically larger than about 175 kg/s, become impractical as
large and heavy fans or ventilators would be required. Large and heavy fans or ventilators required additional
structural supports.
2. A minimum design temperature is required to maintain stability of the smoke layer. Smoke layers which have temperatures approaching that of the replacement air will have a tendency to mix with this air rather than to float above it.
The stipulated minimum design layer temperature is intended to be high enough to allow safe operation of the system for fires which are smaller than the full design size.
Owing to practical limitations, a smoke ventilation system shall have:
(1) a maximum mass flow not exceeding 175kg/s; and
(2) a minimum smoke layer temperature of 18°C above ambient temperature.
i. Replacement air
E
Explanations & Illustrations
Clause 7.4.5i. : Engineered smoke control system
Section
Figure 7.4.5i. - 1
The use of fan-driven inlet air supply can give problems with mechanical extraction. This is because the warmed air taken out will have a greater volume than the inlet air. As the fire grows and declines, the mismatch in volume between the inlet air and the extracted fire warmed air will also change. This can result in significant pressure differences appearing across any doors on the escape routes. Hence, to avoid this “push-pull” effect, replacement air shall be drawn by natural means.
Section
Figure 7.4.5i. - 2
A moving airstream in contact with a region of stationary air (or smoke, or gas) will have a lower pressure than the stationary air – this is the Venturi effect. Hence, a moving airstream will attract the stationary air towards itself. The force of attraction increases with increasing velocity of the airstream. In Figure 7.4.5i – 2, the clean airstream flowing through the door attracts the smoke towards itself. The smoke reservoir base follows the surface of constant pressure, and bulges downwards near the door. Unless the reservoir base is high enough above the door (at least 1.5m), the smoke base will come just below the top of the door.
Section
Figure 7.4.5i. - 3
Where inlets (e.g. door) cannot be sited at least 1.5m below the base of smoke layer, either a smoke curtain or a horizontal shelf could be used to prevent inlet air distorting the smoke layer. Figure 7.4.5i. – 3 shows a smoke-restraining curtain set back from the door. The curtain’s bottom edge is higher than the door. The incoming air stream will increase in vertical section as it travels from the door to beneath the curtain, and so will slow down. There are fewer tendencies to pull down the smoke base. There is less turbulence at the smoke/air interface mixing smoke into the air stream and any such mixed smoke is at a higher level. The curtain shall be more than 3m away from the door.
Section
Figure 7.4.5i. - 4
Using a horizontal shelf instead of a smoke curtain, which permits the same air expansion and gives the same results. The shelf-edge should be more than 3m away from the door.
Amendment History
| 7.4.5i. |
15 Sep 2020 |
15 Sep 2020 |
Clarification |
Replacement air (7) Where the automatic roller shutters are used at replacement air inlets in the design and installation of an engineered smoke control system, it shall be of perforated type having the required effective free area for the effective operation of the engineered smoke control system. |
15 Sep 2020 |
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|
(1) Replacement air shall by natural means be drawn directly from the external space.
(2) The design replacement air discharge velocity shall not exceed 5m/s to prevent the escapees being hindered by the air flow.
(3) Replacement air intake shall be sited at least 5m away from any exhaust air discharge.
(4) Replacement air shall be discharged at a low level, at least 1.5m beneath the designed smoke layer, to prevent fogging up of the lower clear zone.
(5) Where the inlet cannot be sited at least 1.5m below the smoke layer, a smoke curtain or a barrier shall be used to prevent replacement air disrupting the smoke layer.
(6) Where replacement air is taken through inlet air ventilators or door- ways, devices shall be incorporated to automatically open such inlet ventilators and doors to admit replacement air upon activation of the smoke ventilation system.
(7) Where the roller shutters are used as replacement air inlets in the design and installation of an engineered smoke control system or smoke purging system, they shall be of perforated type, having the required effective free area for the effective operation of the engineered smoke control system. Non-perforated type of roller shutters with solid surface shall not be used.
j. Emergency power supply
E
Explanations & Illustrations
Clause 7.4.5j. : Engineered smoke control system
( No Illustration )
All the associated systems/mechanisms, like the door venting actuators, are to be back-up by secondary power supply. This is necessary, as these devices are not incorporated with “standby” batteries that can operate the mechanisms to function as required in the emergency mode.
The engineered smoke ventilation system shall be provided with secondary source of power supply.
k. Mode of activation
(1) Automatic activation
(a) The engineered smoke ventilation system shall be activated by smoke detectors located in the smoke control zone. Use of smoke detectors for activation shall be carefully designed, so that accidental or premature activation of smoke detectors in a non- fire zone (due to smoke spills or spread from other areas) are avoided.
E
Explanations & Illustrations
Clause 7.4.5k.(1)(a) : Engineered smoke control system
(a).tmb-firecode.png?Culture=en&sfvrsn=f8d5221c_1 "Fg.7.4.5k(1)(a)")
Section
Figure 7.4.5k.(1)(a)
Scenario A :
A fire occurring at 3rd storey failed to activate the smoke detector at that level owing to its poor location. Instead, smoke is allowed to spill into the atrium void and smoke control system for the building is activated. This would release all the smoke curtains overlooking the atrium void, including the fire floor, which is not correct. As a result, smoke and heat will be retained in the fire floor. The correct sequence of events should be that the smoke detectors at the fire floor should be activated first, thereby locking the smoke curtain, while releasing all smoke curtains in other parts of the building.
Scenario B :
A fire occurring at the atrium floor caused smoke to spill and activate the smoke detector in 2nd storey. The smoke
curtain will remain locked but at other floors, the smoke curtains will descend down. As a result, part of 2nd storey will be smoke logged.
Smoke control system reacts to the first signal sent by the detector. To overcome the above problem, it is recommended that closer spacing of smoke detectors, closer than the permitted limit in SS CP 10, be adopted and that the detectors should be placed correctly in close proximity of the atrium void.
(b) Provision of activating smoke detectors shall comply with SS CP 10.
E
Explanations & Illustrations
Clause 7.4.5k.(1)(b) : Engineered smoke control system
( No Illustration )
The smoke ventilation system shall operate automatically upon detection of smoke by smoke detector placed strategically at the smoke control zone. The layout of smoke detectors shall comply with SS CP 10.
(2) Manual activation
R
Rationale - Clause 7.4.5k.(2)
The provision of remote manual activation and control switches located at Fire Command Centre or Fire Alarm Panel would permit better controlling of the smoke ventilation system.
In the event of the smoke detectors malfunctioning, the atrium smoke extract system can be activated by a manual switch, which performs the function of the smoke detectors in actuating the associated devices for the isolation and extraction of the smoke from the affected areas.
A remote manual activation and control switches, as well as visual indication of the operation status of the smoke ventilation system, shall also be provided at the FCC. Where there is no FCC, it shall be indicated at the main fire alarm panel.
l. Interlocking with other ACMV systems
E
Explanations & Illustrations
Clause 7.4.5l. : Engineered smoke control system
( No Illustration )
Mechanical ventilation to the following room or space should not be affected:
a. exit staircases and exit passageways;
b. smoke-stop and fire lift lobbies;
c. areas of refuge within the same building;
d. basement car parks;
e. fire command centres;
f. flammable liquid/gas storage room;
g. emergency generator; and
h. engine driven fire pump.
AHUs serving the affected smoke zone are to be shut down automatically upon activation of the smoke ventilation system, while the rest may continue to function.
Except for ventilation systems in Cl.5.2.1g. and Cl.5.2.1h., all other air-conditioning and mechanical ventilation systems within the areas served shall be shut down automatically upon activation of the smoke ventilation system.
m. Standby fans/ multiple fans
(1) Either a standby fan or multiple fans with excess capacity shall be provided for each mechanical smoke ventilation system, such that in the event the duty fan or the largest capacity fan fails, the required smoke extraction rate will still be met. The standby fan shall be automatically activated in the event the duty fan fails.
E
Explanations & Illustrations
Clause 7.4.5m.(1) : Engineered smoke control system
.tmb-firecode.png?Culture=en&sfvrsn=e907782a_1 "Fg.7.4.5m(1)")
Section
Figure 7.4.5m.(1)
(2) Fans shall be capable of operating at 250°C for 2 hours.
(3) Protected circuits
R
Rationale - Clause 7.4.5m.(3)
Since the smoke control system is installed to remove smoke and heat from the building to aid evacuation of occupants and firefighting operations, the system’s circuits shall be protected to ensure operational reliability and sustained operation during fire emergency.
The fans and associated smoke control equipment shall be wired in protected circuits designed to ensure continued operation in the event of fire.
(4) Electrical supply
R
Rationale - Clause 7.4.5m.(4)
The main purpose is to ensure that the electrical supply to the fans could be maintained continuously for at least 1 hour.
The electrical supply to the fans shall, in each case, be connected to a sub-main circuit exclusive thereto after the main isolator of the building. The cables shall be of at least 1-hr fire resistance rating in accordance with SS 299.
n. Smoke ventilation ducts
(1) Smoke ventilation ducts (both exhaust and replacement air ducts) shall be of at least 1-hr fire resistance rating. The rating shall apply to fire exposure from both the interior and exterior of the duct or structure and the duct shall also comply
with Cl.7.1.2h..
(2) Where a duct passes through another fire compartment with higher fire rating, the duct shall be constructed to have fire-rating as that of the compartment. Where a duct is installed in a single fire compartment and does not pass through another compartment,
smoke control ducts (both exhaust and replacement air ducts) within that compartment need not comply with the 1-hr fire resistance rating requirement subject to the following conditions:
(a) the smoke ventilation ducts (both exhaust and replacement air ducts) are constructed of at least 1.2mm thick galvanised steel sheet;
(b) sprinklers, designed to SS CP 52, shall be provided above and below the entire length of the ducts (regardless of the duct dimensions) to protect the duct surfaces from the effect of water spray through the activated sprinklers; and
(c) the construction and support of the duct shall conform to the appropriate requirements of the duct construction standards contained in ASHRAE Handbook, IHVE Guild books or SMACNA Manuals.
Amendment History
| 7.4.5n |
|
17 Apr 2015 (circular portion), 01 Mar 2019 (revised portion) |
Revised, formerly Cl.7.6.24. Extracted from SCDF's circular. |
|
17 Apr 2015 |
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o. Fire damper
(1) Fire dampers shall not be fitted in the smoke ventilation system, except where used in an engineered smoke control system. In such a situation, a combination of fire and smoke dampers shall be constructed in accordance with SS 333, and its electric actuator shall be tested in accordance with the requirements of UL 555S for at least 2 hours at 250ºC.
(2) The damper shall be in closed position during fail-safe mode.
(3) The combination fire and smoke damper, and any duct extension between it and the protected vent shaft, shall be of the same rating as the element of structure.
(4) Sprinkler protection shall be provided to the electric actuator.
(5) The electrical power supply cables to the electric actuator shall be fire resistant.
Amendment History
| 7.4.5o.(2) to (5) |
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01 Mar 2019 |
New |
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p. The time taken for a smoke ventilation system within a smoke zone to be fully operational shall not exceed 60 secs from the time of activation.
q. Fail-safe system
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Explanations & Illustrations
Clause 7.4.5q. : Engineered smoke control system
Section
Figure 7.4.5q.
Wrong positioning of roof ventilators can cause the wind to be deflected into the atrium roof space, thereby pushing the smoke downward into the building. Roof adjacent to tall buildings could be subjected to positive pressure. It is for the designer to prove that his design will be satisfactory.
For natural smoke ventilation system, the natural ventilators shall be-
(1) in the “open” position in the event of power/system failure; and
(2) positioned such that they will not be adversely affected by positive wind pressure.
r. Natural ventilation shall not be used together with mechanical ventilation.
E
Explanations & Illustrations
Clause 7.4.5r. : Engineered smoke control system
Section
Figure 7.4.5r.
The combination of natural exhaust ventilation and powered smoke exhaust ventilation in a building would create complications on the design of the distance between the bottom of the smoke reservoir and the floor and also the extent of the depth of the smoke reservoir.
s. Smoke curtain
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Rationale - Clause 7.4.5s
The intent of the smoke curtain is to contain the smoke and to prevent spillage of smoke to other areas.
All smoke curtains, where required, unless permanently fixed in-position, shall be brought into position automatically to provide adequate smoke-tightness and effective depth.
t. Obstruction to means of escape
E
Explanations & Illustrations
Clause 7.4.5t. : Engineered smoke control system
Section
Figure 7.4.5t.
Upon activation of smoke detector, the smoke curtain is automatically unfurled from its roller under gravity fall to impede smoke flow. The dropped curtains limit the area of smoke spread, maintain visibility and tenable conditions for escape purposes.
Smoke curtain in operation should not obstruct the escape routes. The clear height of smoke curtain across the escape routes should not be lower than 1.8m from its finished floor level.
A smoke curtain, or other smoke barrier, located at any access route forming part of or leading to a means of escape, shall not in its operational position obstruct said escape route.
u. Smoke or chanelling screens
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Explanations & Illustrations
Clause 7.4.5u. : Engineered smoke control system
Figure 7.4.5u. - 1
Wired glass or tempered glass could be used as smoke screen to form smoke reservoir, provided they are able to meet the designed highest temperature. Glass walls or panels acting as smoke screen shall not be of sliding, louvers or openable type.
Section
Figure 7.4.5u. - 2
Smoke screens, which are to meet the designed highest temperature, could be used to form smoke reservoirs to limit lateral spread. Smoke channelling screens are used to channel smoke away from the origin of fire to smoke reservoirs where extraction can be carried out, or away from the building entrance canopies to the external open space as shown above.
It is recommended that the spacing between channelling screens should not be more than 14m so as to prevent lateral spread of smoke and excessive cooling.
Where glass walls or panels are being used as smoke screens to form a smoke reservoir or as channelling screens, they shall be able to withstand the design highest temperature.
v. All smoke control equipment (including smoke curtains) shall be supplied and installed in accordance with BS EN 12101-1, BS EN 12101-3 and BS 7346 Pt 7 or equivalent.
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Explanations & Illustrations
Clause 7.4.5v. : Engineered smoke control system
( No Illustration )
Fixed screen shall be constructed of non-combustible materials capable of resisting the highest design temperatures. Automatic retractable smoke curtains are required to comply with BS 7346 and listed under Product Listing Scheme.
Amendment History
| 7.4.5v |
10 May 2019 |
9 Nov 2019 |
New requirement |
All smoke control equipment (including smoke curtains) shall be supplied and installed in accordance with BS 7346 or equivalent. |
10 May 2019 |
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