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Legend: Explanations & Illustrations Rationale Note Revision history Print

Clause 7.1 - AIR-CONDITIONING AND MECHANICAL VENTILATION SYSTEMS

7.1.1 General

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Where an air-conditioning system is provided in lieu of a mechanical ventilation system for emergencies, all the requirements specified in this Code for mechanical ventilation systems shall apply to the air-conditioning system.

7.1.2 Construction of ductwork

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Ducts for air-conditioning and mechanical ventilation systems shall be constructed in compliance with all of the following requirements:

a. Materials

Air-conditioning or other ventilation ducts, including framing thereof, shall be constructed of steel, aluminium, glass fibre batt or mineral wool batt or other approved materials. 

b. Support 

Air-conditioning or other ventilation ducts shall be adequately supported. 

c. Duct linings & coverings

Duct covering and lining shall be non-combustible. However, if it is necessary to use combustible material, it shall:

(1) when tested in accordance with methods specified in this Code, have a surface flame spread rating of not lower than Class 1, except in areas of a building where Class 0 flame spreading rating is required for the ceiling construction under this Code, a Class 0 rating for the covering and lining materials shall instead be required;

(2) when involved in fire, generate a minimum amount of smoke and toxic gases; and

(3) be at least 1m away from a fire damper.

d. Flexible joints and connections

(1) Flexible connections at the ends of ventilation ductwork connecting terminal units, extract units and ventilation grilles shall not exceed 4m.

(2) Flexible joints, which are normally provided to prevent and/or allow for thermal movements in the duct system, shall not exceed 250mm in length.

(3) Flexible joints shall be made of material classified as ‘not easily ignitable’ when tested under BS 476: Part 5.

e. Duct enclosure

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Enclosure of ducts shall comply with the requirements in Cl.3.8.9a..

f. Ductwork through smoke-stop or fire lift lobbies

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Ventilation ducts should not pass through smoke-stop or fire lift lobbies. Where unavoidable, the part of the ventilation duct within the lobby shall be enclosed in masonry construction with fire resistance rating at least equal to that of the elements of structure. If other forms of fire resisting construction are used, a fire damper shall be fitted where the duct penetrates the lobby enclosure.

g. Ductwork through separating walls

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No air-conditioning or ventilation duct shall penetrate separating walls.

h. Fire-rated duct

(1) Where proprietary fire-rated materials are used to construct the fire- rated duct, the fire rating of the fire-rated duct shall have the same period of fire resistance as the wall or floor it penetrates.

(2) Proprietary fire-rated duct shall be tested to BS 476 Pt 24 or equivalent and its usage be approved by the SCDF.

(3) Running of non-fire-rated duct and/or other building services above the proprietary fire-rated duct should be avoided. When unavoidable due to physical constraints, the supports to such non-fire-rated duct and/or other building services running above the proprietary fire-rated duct shall be strengthened, such that the tensile stress generated on the supports shall not exceed 10N/mm2. The non-fire-rated duct and/or building services shall also be adequately protected to prevent collapse in a fire which will otherwise affect the stability of the proprietary fire- rated duct below.

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(4) Fans forming part of a fire-rated duct shall also be enclosed in the same fire-rated enclosure.

(5) Control panels serving engineered smoke control and smoke purging systems shall be clearly visible and located within a common location readily accessible for operation and maintenance, preferably within circulation space, with a mounting height of not less than 1.5m or more than 1.8m from the finished floor level. For smoke purging systems in car parks, the control panel shall be sited at least 1.5m away from any car park lot or other fire hazards. If a common accessible location is not possible, the control panels shall be protected with at least 1-hr fire resistance rating.

R Rationale - Clause 7.1.2h.(5)

The control panel serving the fans of smoke control systems are crucial and should not be located within any smoke layer to ensure that the integrity of the smoke control system is not compromised in an fire emergency. The exhaust systems would not be operable in the event of failure of the control panels.

7.1.3 Pipework

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Insulation for pipework associated with the air-conditioning and mechanical ventilation systems shall comply with the following requirements:

a. Flame spread rating

Insulation material for pipework, together with vapour barrier lining and adhesives shall, when tested in accordance with the methods specified in this Code, have a surface flame spread of not lower than Class 1. However, in areas of buildings where Class 0 flame spread is required for the ceiling construction under this Code, a Class 0 rating for the insulation material shall be required.

b. Plastic and foam rubber insulation

Notwithstanding the requirements of Cl.7.1.3a., the use of plastic and foam rubber insulation materials of a lower classification is permitted if:

(1) it is of the self-extinguishing type; and

(2) the insulation is covered by or encased in a metal sheath or hybrid plaster or other non-combustible cladding material,

provided that any opening in the element of structure or other part of a building penetrated by the pipework shall be effectively fire-stopped by replacement of the insulation material at the junction of penetration with fire resistant material having equal fire resistance rating. A fire-rated proprietary pipework system can be used if it is tested in the manner acceptable to the SCDF.

7.1.4 Air plenum

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A concealed space between the ceiling and floor above it, ceiling and roof, or raised floor and structural floor of a building can be used as a plenum provided:

a. The concealed space contains only:

(1) mineral insulated metal sheathed cable, aluminium sheathed cable, copper sheathed cable, rigid metal conduit, enclosed metal trunking, flexible metal conduit, liquid tight flexible metal conduit in lengths not more than 2m, or metal-cladded cables;

(2) electric equipment that is permitted within the concealed spaces of such structures, if the wiring materials, including fixtures, are suitable for the expected ambient temperature to which they will be subjected;

(3) other ventilation ducts complying with Cl.7.1.2a. to d.;

(4) communication cables for computers, television, telephone and inter-communication systems;

(5) fire protection installations; and

(6) pipes of non-combustible material conveying non-flammable liquids.

b. The supports for the ceiling membrane are of non-combustible material.

c. Exception

Low-smoke and low-flame plenum rated PVC cables conforming to NFPA 262 can be run exposed in plenum, provided that:

(1) the plenum space is protected by a sprinkler system or gaseous total flooding system; and

(2) a FCU or AHU using a plenum for air return and serving more than one room, is installed with smoke detector(s) at the return air plenum space to shut down the FCU/AHU upon detection of smoke.

7.1.5 Fire Dampers

Any fire damper shall have a fire resisting rating of not less than that required for the compartment wall or compartment floor through which the relevant section of the ventilation duct passes. Fire dampers shall be of the type approved by the SCDF and constructed in accordance with the requirements in SS 333.

a. Provision of fire dampers

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Ventilation ducts which pass directly through a compartment wall or compartment floor shall comply with the following:

(1) where the ventilation duct does not form a protected shaft or is not contained within a protecting structure, the duct shall be fitted with a fire damper where it passes through the compartment wall or compartment floor; and

(2) where the ventilation duct forms a protected shaft or is contained within a protecting structure, the duct shall be fitted with fire dampers at the shaft inlets and outlets.

b. Installation of fire dampers

(1) Fire dampers shall be installed so that the casing completely penetrates through the compartment wall or floor, and the casing shall be retained, either:

(a) on both sides by means of flanges in such a manner that it can expand under fire conditions without distorting the blades in the closed position, or

(b) on the accessible side by means of one flange only, which can be fixed to the damper and to the wall through slotted holes to allow for expansion.

(2) Flanges shall be butted against the face of the compartment wall or floor and fixed to the damper casing.

(3) Ductwork connected to the damper shall be attached in such a manner as to ensure that the damper remains securely in position and is fully functional in the event of damage of ductwork.

(4) The clearance between the damper body and the sides of the penetration shall not be less than that of the tested prototype and be not greater than half the width of the angled section of the collar.

(5) The space between the damper body and the opening in the wall or floor shall be fire-stopped.

(6) Vertically positioned fire dampers shall be installed in such a manner that the direction of air flow assists in the closure of the damper.

(7) Connections to fire dampers

The distance between the plane through a closed fire damper and ducting, flexible connections, duct coverings, internal linings and the like, shall be

(a) not less than 1m when such parts are made of materials with fusing temperatures less than 1000oC;

(b) not less than three times the diagonal or diameter of the damper; and

(c) not less than 2m when such parts are made of materials that are combustible, except for vapour barrier to provide thermal insulation.

(8) Fire damper inspection access doors

Each fire damper installation shall be provided with an inspection access door in the ventilation duct, either upstream or downstream, as appropriate. The access door dimension shall measure 450mm (length) X 450mm (width); for smaller ducts, the door width dimension can be reduced to the width or depth of the duct. Access doors shall be hinged and fitted with sash locks, and be constructed of minimum 1.25mm suitably braced sheet steel. Openings in ducts shall be stiffened by a sheet steel frame.

c. Prohibition of fire dampers

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Fire dampers shall not be fitted in any of the following locations:

(1) openings in walls of a smoke extract shaft, or a return air shaft which also serves as a smoke extract shaft, or

(2) openings in walls of a protected shaft when the openings have a kitchen exhaust duct passing through it, or

(3) opening in walls of a protected shaft when the openings have a fume hood exhaust duct passing through it, or

(4) anywhere in an air pressurising system, or

(5) in locations explicitly prohibited in this Code.

d. Standards

Where a fire damper is required by this Code to be installed in an air- conditioning and mechanical ventilation system, its type, details of installation, connection of accessories, inspection door, etc., shall be in accordance with SS CP 333.

7.1.6 Fire resisting floor ceiling and roof ceiling

a. The space above a suspended ceiling which forms part of a fire-rated floor ceiling or roof ceiling construction shall not contain ducting, unless said ducting was incorporated in a prototype that qualified for the required fire resistance rating, in which case the ducting shall be identical to that incorporated in the tested prototype.

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b. Openings in the ceiling, including openings to enable the ceiling to be used as a plenum, shall be protected by fire dampers identical to those used in the tested prototype. Such openings in the ceiling shall be so arranged that:

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(1) no opening is greater in area than that in the corresponding prototype test panel;

(2) the aggregate area of the openings per unit ceiling area does not exceed that of the prototype test panel; and

(3) the proximity of any opening to any structural member is not less than that in the prototype test panel.

7.1.7 Locations of intakes and return air openings

a. Openings for the intakes of outdoor air to all air handling systems, mechanical ventilation systems, pressurisation systems of exit staircases and internal corridors, and smoke control systems shall be no less than 5m from any exhaust discharge openings.

b. All return air openings and outdoor air intakes shall be located and arranged such that sources of ignition, such as lighted matches and cigarette butts, which accidentally enter the openings and intakes cannot be deposited onto the filter media.

7.1.8 Air handling unit (AHU) room

a. Air plenums

Air handling systems shall not use protected shafts of exits, smoke-stop lobbies, including its concealed space for supply, exhaust or return air plenums.

b. Compartmentation

R Rationale - Clause 7.1.8b

Rooms having no usage other than housing air handling equipment or package units, and their associated electrical controls are typically not regarded as areas of high risk and therefore compartmentation is not required. However, fire dampers shall be provided within the air ducts of the air handling equipment where they penetrate through compartments to prevent fire spread.

(1) Where the air handling equipment serves more than one compartment, fire dampers shall be provided in air ducts at penetrations through the compartment walls and floors to comply with the requirements in Cl.7.1.5.

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(2) Where AHU rooms are vertically stacked, each AHU room shall be separated by a compartment floor at every level.

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c. Smoke detectors

(1) Smoke detectors of approved type shall be incorporated in the return air stream immediately adjacent to:

(a) AHUs serving more than one storey or compartment, or

(b) a single AHU in excess of 15000 m³/h.

(2) The function of smoke detectors, where required by this Code, is to initiate action to shut down the AHU automatically when the smoke density in the return air system has become unacceptable for recycling.

d. Stop switch

Where the AHUs in a building are not centrally controlled, each AHU exceeding 8500m³/h shall be provided with a manual stop switch to facilitate quick shutting down of the fan in the case of fire. For ease of access, this switch shall be located on the wall next to the door opening of the air handling equipment room.

7.1.9 Ventilation system for exits

a. Air plenums

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Protected shaft of exits, smoke-stop lobbies, including their concealed spaces shall not be used for supply, exhaust or return air plenum of air handling systems.

b. Exit staircase and internal exit passageway

A mechanical ventilation system for each exit staircase and internal exit passageway, if provided, shall be an independent system of supply mode only exclusive to the particular staircase, and it shall comply with all of the following requirements:

(1) Supply air for the system shall be drawn directly from the external space, with intake point not less than 5m from any exhaust discharge openings.

(2) For exit staircase serving more than four storeys, supply air shall be conveyed via a vertical duct extending throughout the staircase height and discharging through outlets distributed at alternate floors.

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(3) Where the supply air duct serving the exit staircase has to penetrate the staircase enclosure, the portion of the duct where it traverses outside the staircase shall be enclosed in masonry construction or drywall complying with Cl.3.8.7b. of at least the same fire resistance as the elements of structure, and it shall not be fitted with fire dampers.

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(4) The ventilation system shall be of supply mode only, and of not less than 4 air changes per hour.

(5) The mechanical ventilation system shall be automatically activated by the building fire alarm system. In addition, a remote manual start-stop switch shall be made available to firefighters at the FCC, or, where there is no FCC, at the fire alarm panel.

(6) Visual indication of the operational status of the mechanical ventilation system shall be provided.

7.1.10 Ventilation system for smoke-stop lobby and fire lift lobby

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a. The ventilation system shall be of supply mode only of not less than 10 air changes per hour.

b. Supply air shall be drawn directly from the external space with intake point not less than 5m from any exhaust discharge or openings for natural ventilation.

c. Any part of the supply duct running outside the smoke-stop or fire lift lobby which it serves shall either be enclosed or constructed to give a 1-hr fire resistance rating. The SCDF may, at its discretion, require a higher fire resistance rating if the duct passes through an area of high fire risk.

d. The mechanical ventilation system shall be automatically activated by the building fire alarm system. In addition, a remote manual start-stop switch shall be made available to firefighters at the FCC, or, where there is no FCC, at the main fire alarm panel.

e. Visual indication of the operational status of the mechanical ventilation system shall be provided.

7.1.11 Ventilation system for engine-driven fire pump room and generator room

Where mechanical ventilation is installed to provide a smoke-free environment for the room housing the engine-driven fire pump or emergency generator, such systems shall be independent of each other and of any other system serving other parts of the building, and shall comply with all of the following requirements:

a. Supply air shall be drawn directly from the external space and its intake point shall not be less than 5m from any exhaust discharge openings. Exhaust discharge shall also be direct to the external space.

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b. Where the corresponding ducts run outside the room they shall either be enclosed in a structure or be constructed to give at least the same fire rating as the room which they serve, or that of the room through which they traverse, whichever is higher. The rating shall apply to fire exposure from both interior and exterior of the duct or structure. Where the duct risers are required to be enclosed in a protected shaft constructed of masonry or drywall complying with Cl.3.8.7b., they shall be compartmented from the rest of the shaft space containing other ducts or service installations.

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c. No fire damper shall be fitted in either supply or exhaust duct required under this clause.

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d. A duct serving areas other than rooms housing equipment stated in this clause shall not pass through such rooms.

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7.1.12 Ventilation system for Fire Command Centre (FCC)

The FCC can either be air-conditioned, naturally ventilated or mechanically ventilated. The air-conditioning or mechanical ventilation shall be independent of each other and any other system serving other parts of the building. Where mechanical ventilation is required, it shall also comply with all of the following requirements:

a. Supply air shall be drawn directly from the external space and its intake point shall not be less than 5m from any exhaust discharge openings. Exhaust discharge shall also be direct to the external space.

b. Where the corresponding ducts run outside the FCC, they shall either be enclosed in a structure or be constructed to give at least the same fire rating as the room which they serve or that of the room through which they traverse, whichever is higher. Where the duct risers are required to be enclosed in a protected shaft constructed of masonry or drywall complying with Cl.3.8.7b., they shall be compartmented from the rest of the shaft space containing other ducts or service installations.

c. No fire damper shall be fitted in either supply or exhaust duct required under this Clause.

d. A duct serving areas other than the FCC shall not pass through the room.

7.1.13 Exhaust system for kitchen

a. Provision

A mechanical exhaust system for the cooking area of a kitchen in a hotel, restaurant, coffee house or the like shall be independent of those serving other parts of the building. It shall also comply with all of the following requirements:

(1) The hood and ducts for the exhaust shall have a clearance of 500mm from unprotected combustible materials.

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(2) The exhaust shall discharge directly to the external space and shall not be less than 5m from any air intake openings.

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(3) The exhaust duct, where it runs outside the kitchen, shall either be enclosed in a structure or be constructed to give at least the same fire rating as the kitchen or that of the room through which it traverses, whichever is higher. The rating shall apply to fire exposure from both interior and exterior of the duct or structure. Where the duct riser is required to be enclosed in a protected shaft constructed of masonry or drywall complying with Cl.3.8.7b., it shall be compartmented from the rest of the shaft space containing other ducts or services installations.

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(4) No fire damper shall be fitted in kitchen exhaust ducts.

b. Sharing of kitchen exhaust system

Sharing of kitchen exhaust system for food and beverage outlets is allowed, provided all of the following conditions are complied with:

(1) For food courts

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(a) The food court shall be under a single ownership/operator.

(b) All kitchen exhaust ducts running outside the food court shall have 1-hr fire resistance rating, or shall not be less than that for the elements of structure, whichever is higher.

(2) For restaurants/small F&B outlets (e.g. snack bars, food kiosks, etc.)

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(a) Restaurants and small F&B outlets that are sharing the same kitchen exhaust system shall be located on the same storey and within the aggregate zone area not exceeding 2000m2. The maximum length of the aggregate zone covering from the first to the last restaurant/F&B outlet shall not exceed 50m.

(b) The aggregate floor area of the restaurants and F&B outlets shall not exceed 1000m2.

(c) Common ducts shall be provided with a common exhaust fan.

(d) The building shall be protected by an automatic fire sprinkler system.

(e) The exhaust hood shall be fitted with a wet chemical fire extinguishing system.

(f) The fire rating of the common kitchen exhaust duct running outside the restaurants shall have 1-hr fire resistance rating, or shall not be less than that for the elements of structure, whichever is higher.

(Note: Kitchen exhaust ducts include both horizontal and vertical ducts.)

c. Kitchen exhaust duct

(1) A kitchen exhaust duct running outside a building shall not be located within 3m of any unprotected openings. This separation distance can be reduced to 1.5m if the unprotected opening is on the same plane as the duct. (See Diagram 7.1.13c.(1) - 1 and 2)

(2) Where the distances mentioned above cannot be achieved, a fire resistant construction having at least ½-hr fire resistance shall be placed between the duct and the unprotected opening. (See Diagram 7.1.13c.(2))

(3) A non-fire-rated kitchen exhaust duct shall not be located above an LPG storage cabinet, unless they are separated from LPG cylinders by a minimum of 2-hr fire-rated masonry construction above and beside the cylinders. (See Diagram 7.1.13c.(3))

(4) The kitchen exhaust duct shall be located at least 3m from any unprotected LPG cylinders. Non-fire-rated kitchen exhaust duct shall be located at least 600mm from the vapouriser or any liquid-phase LPG pipeline. (See Diagram 7.1.13c.(4))

d. Maintenance

! Note to QPs on Clause 7.1.13d

Building owners, MCSTs and eating outlet operators shall ensure that the entire (interior and exterior) kitchen exhaust duct and kitchen hood shall be degreased and cleaned at least once every 12 months. The work shall be carried out by a specialist and the records of cleaning and degreasing shall be kept by the owner/MCST/operator for verification by the authority having jurisdiction.

All kitchen exhaust systems shall be properly maintained. The entire (interior and exterior) exhaust duct and kitchen hood shall be degreased and cleaned at least once every 12 months. The work shall be carried out by a specialist and the records of cleaning and degreasing shall be kept by the owner/operator for verification by the authority having jurisdiction. This requirement shall be included in the Fire Safety Instruction Manual

7.1.14 Ventilation system for rooms involving use of flammable and explosive substances

a. Dedicated system

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Mechanical ventilation systems, where required for rooms which involve the use of flammable and explosive substances, shall be independent from those serving other parts of the building. They shall comply with all of the following requirements:

(1) Ventilation system shall consist of exhaust and supply parts with a rate of 20 air changes per hour or any other rates acceptable to the SCDF. The exhaust shall direct to the external space and shall not be less than 5m from any air intake openings.

(2) Where such ducts run outside the room they shall either be enclosed in a structure or be constructed to give at least the same fire rating as the room which they serve or that of the room through which they traverse, whichever is higher. The rating shall apply to fire exposure from both interior and exterior of the duct or structure. Where the duct risers are required to be enclosed in a protected shaft constructed of masonry or drywall complying with Cl.3.8.7b., they shall be compartmented from the rest of the shaft space containing other ducts or service installations.

(3) No fire damper shall be fitted in either a supply or exhaust duct required under this Clause.

(4) Ducts serving other areas shall not pass through rooms involving use of flammable and explosive substances.

b. Sharing of supply air duct

A common fire-rated supply air duct can serve various compartments within the same floor level or other floor levels, provided:

(1) the compartments are sprinkler-protected;

(2) the compartments are of the same purpose group;

(3) the duct is fitted with a fire damper where it passes through the wall or floor of each fire compartment; and

(4) a dedicated exhaust duct is provided for individual fire compartments and shall be maintained in operation (with the minimum flow rate) even it is under fire mode situation to prevent smoke entering into other fire compartments.

7.1.15 Ventilation system for rooms housing batteries

Rooms housing batteries shall comply with the following requirements:

a. The batteries shall be of either vented or sealed type.

b. The room ventilation system shall be designed to limit the maximum concentration of Hydrogen (H2) gas to 1% of the total volume of the room during the worst case event of simultaneous “boost” charging of the batteries. The inlets and outlets of the ventilation system shall be properly located so that there is no stagnant area in the room.

R Rationale - Clause 7.1.15b

The revision is in line with NFPA to limit the maximum concentration of hydrogen to 1% of the total volume of the room. The ventilation rate for the room shall be computed in accordance with BS EN IEC 62485 or 6 air changes, whichever is higher.

c. Adequate hydrogen gas detectors shall be provided inside the room to monitor the hydrogen concentration and to activate the fan, if necessary, to ensure that the hydrogen concentration level at any part of the room does not exceed 1% of the total volume of the room. Display panels showing the readings of the detectors shall be located at the entrance to the room. At the same time, an alarm signal shall be sent to a manned station such as security control room, guard house or FCC.

d. The design of the battery room ventilation shall be in accordance with BS EN IEC 62485-2 & BS EN IEC 62485-3.

e. For mechanically ventilated battery rooms, the ventilation requirement shall be based on Cl.7.1.15d., or 6 air changes per hour, whichever is higher.

f. No fire damper shall be provided in the essential ventilation system and ducts passing through other compartments shall have 2-hr fire resistance rating.

g. Essential fans and associated electrical controls shall be backed up with a secondary source of power supply.

Last Updated: 20 February 2019