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Unit 5: Fire Safety Installations

5.1 Basic Fire Sciencei. Definition of Fire: A process of combustion accompanied by a

rapid release of heat and light in varying quantities.ii. By products of fire: Gas and smoke. These products can impede

oxygen levels as well as causing visual impairment, leading toasphyxiation as well as inhibiting swift evacuation from building.

iii. Triangle of Fire: Combustion requires 3 elements in order to takeplace:

a) Fuel: Combustible solids, liquids or gases;b) Heat:c) Oxygen: Makes up approx. 21% of Earth’s atmosphere.

iii. Classes of Fires:a) Class A Fires: Ordinary, combustible materials, e.g Paper, wood, etc;b) Class B Fires: Flammable or combustible liquids, liquids or gases,

such as petroleum related products;c) Class C Fires: Energized electrical equipment (i.e Electrical Fires);d) Class D Fires: Combustible Metals, e.g Potassium, sodium, titanium,

etc.

Triangle ofFire

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5.2 How Fires are Extinguishedi. Fires can be extinguished by removing any one element from the

triangle of fire:– Cutting off the oxygen supply to the fire, e.g Using a blanket to

smother the fire;– Removing fuel supply to the fire, e.g cutting off the gas supply to the

stove will cut off the stove fire;– Removing heat supply the fire via cooling, e.g spraying water into the

fire.Types of Fire Fighting Systems

ii. Automatic fire fighting system: Includes sprinklers, foams, FM200;iii. Manual Fire Fighting equipment: Includes water hose reels, hydrants,

fire extinguishers;iv. Fire Alarm Systems: Designed to alert nearest fire station as well as in-

house fire fighting team to fight fire.

5.3 Manual Fire Fighting Systems5.3.1 Fire Extinguishers:i. Common Types of Extinguishing Agents

for Portable Fire Extinguishers: Water; Carbon Dioxide (CO2); Halon; Powder; Foam.ii. All extinguishers in buildings must be

charged, tested and maintained inaccordance to locality’s code ofpractice (SS: CP 55 in Singapore);

iii. Construction of Extinguishers inconformance to COP of locality (SS232for Singapore).

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iv. Types of Extinguishersa) Water: Extinguishing method: Removing heat source (Cooling); Removing oxygen source (Smothering);

Can be discharged from: Portable Extinguishers; Water hose reels (Connected to a main water supply line) or other forms

of water sprays; Fire Hydrants; Dry/Wet risers.

Advantages: Easily available as long as there is a consistent water supply; Cheap; High Specific Heat Capacity (4.2kJ/kg at atmospheric pressure) and High

latent heat of vaporization: (225kJ/kg at atmospheric pressure): Able tocool effectively through high heat absorption;

When vaporized, water expands up to 1600 times its original volume.This allows it to displace oxygen in the air, hence the smothering effect.

Disadvantages: Water is an excellent conductor of electricity, hence unsuitable for

Class C electrical fires; Not suitable for Combustible Metals (Class D fires); Not suitable for continuous use on radioactive substances; Tends to damage properties when used to extinguish fires.

Suitable classes of fire for water: Class A and Class B Fires.

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b) Carbon Dioxide (CO2): Extinguishing method: Removing oxygen source (Smothering);

Advantages: Non-combustible; Does not conduct electricity, hence suitable for all electrical fires; Easily liquefied and bottled; Low Boiling Point: Once discharged, it immediately vaporizes and

displaces the oxygen in the air, hence achieving the smothering effect onthe fire;

Since CO2 is a gas, it dissipates into the atmosphere readily, leaving notraces behind and hence no damage to property;

Can penetrate to all areas due to its gaseous form.

Disadvantages: CO2 is limited in putting out fires due to its readiness to dissipate into

the environment and low cooling capacity; Requires large quantities to put out large or deep seated fires; May create suffocating atmosphere in enclosed areas due to its ability

to displace oxygen; Should only be used when there is a nearby escape route for occupants

to evacuate before discharge. Suitable Classes of Fire for CO2: Classes A, B, C and D fires.

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c) Halon Extinguishing method: Removing oxygen source

(Smothering). Halon is a form of hydrocarbon: One of

the hydrogen atoms replaced byflourine, bromine, chlorine or Iodine.

Can be discharged from: Total flooding systems; Portable Fire Extinguishers.

Advantages: Non-flammable; Does not conduct electricity, hence

suitable for all electrical fires; Does not leave behind messy

residues; Does not damage sensitive

electronic equipment; Suitable for server rooms.

Suitable Classes of Fire for Halon: Classes A, B and C fires. Disadvantages: Expensive; Toxic: Evacuate occupants before usage. Limitations in exposure time

and concentration levels; Environmental Issue 1: Depletion of Ozone in Earth’s Upper

Atmosphere; Environmental Issue 2: Creates Greenhouse Effect by trapping heat in

Earth’s atmosphere; Limits of quantities used by Montreal Protocol. In Singapore, installation of Halon Systems have ceased since 1990; Not suitable for the following fires:

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d) Dry Powder Extinguishing method: Removing oxygen source (Smothering); Removing heat source (Cooling).

How it works: Uses chemical particles to extinguish fire; Forms a barrier to reduce oxygen required for combustion; Crust forms over burning material as heat reacts with the powder, further

smothering the fire via cooling. Usually discharged from Portable Fire Extinguishers. Advantages: Good for normal combustibles involving surface fires, as it puts out fire

rapidly; Chemical cloud provides effective screen against flame flashback, allowing user

to close in on fire safely to put out fire more effectively; Forms radiant heat barrier (Crusting).

Disadvantages: Leaves behind messy residue. Will cause damage to electronic

equipment; Does not leave behind lasting inert atmosphere on surface. If ignition

is expected, dry powder is not adequate; Toxic: May be detrimental to health.

Suitable classes of fire for Dry Powder: Classes AB or BC (Class D isavailable as well, but rare).

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e) Foam

Extinguishing method: Removing oxygen source

(Smothering); Removing heat source (Cooling).

How it works: Special liquid agentsmixed with air (sometimes a inertgas) to create foam concentrate; Ability to expand: In liquid form,

it blankets fire and forms layerover burning material to smotherfire;

Vaporized vapor inhibits oxygenfrom feeding fire;

Some foam mixtures can formvapor seal to blanket overburning material.

Defined by their ability to expand:

Advantages: Effective for fuel-related fires; When doused over fuel spills, fuel is rendered safe from combustion; Because it is in liquid and/or vapor form, it can be used to spray into

small spaces where there is suspected fuel residues; In vapor form, it can be used to disperse fuel vapors and reduce

oxygen levels via steam displacement. Disadvantages: Water based, so foams are excellent conductors of electricity and

cannot be used for electrical fires; Due to its water based nature, foam is unstable and it can easily be

broken down and dispersed. Large volumes required to put out fire; Easily diverted away from fire areas under strong winds.

• Suitable classes of fire for Dry Powder: Classes A and B fires.

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v. How Fire ExtinguishersWork

Activating the fire extinguisher – GasCartridge Typea) Pull the safety pin. This will unlock

the lever;b) Aim nozzle at base of the fire and

press the lever;c) When lever is depressed, actuating

rod pushes down and activates thespring-mounted valve;

d) End of actuating rod is a needlewhich activates the gas releasevalve connected to the gascartridge;

e) Gas is released from the cartridgeand the suppressant/extinguishingagent is released from the fireextinguisher.

Components of the Gas Cartridge FireExtinguisher

Activating the fire extinguisher –Stored Pressure Typea) Similar in operation to gas

cartridge type;b) Nozzle may be replaced by

extended hose and horn typenozzle;

c) Triggering the lever will siphonthe suppressant through thesyphon tube all the way to thehorn to be expelled.

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vi. Maintenance of Fire Extinguishers

a) Mandated by law.b) Maintenance of fire extinguishers are focused on three basic elements: Mechanical parts; Extinguishing agent/suppressant; Means of Expulsion.

c) Regular Maintenance (Usually once a year) will include the followingcheck list:– Location of the extinguisher at its designated location;– Extinguisher is free from obstruction in terms of visibility and

accessibility;– Operating instructions visible, facing outward;– Seal and tamper indicators are still in place;– Weighing of extinguisher to ensure suppressant quantity is adequate;– Check pressure gauge reading;– Check external nozzle for blockage, body of extinguisher free from

physical damage and corrosion.

d) Under the following circumstances, increase in frequency of inspectionsshould be considered: High frequency of fire hazards in the location; Extinguishers subjected to external damage or losses: Vandalism, theft,

abuse due to impact from external forces, etc; Exposure to abnormal atmospheres or temperatures; Presence of physical obstructions; Condition of deteriorating fire extinguishers.

e) Schedule for Recharging of Extinguishers: Extinguishers must berecharged after a stipulated time period or immediately after use.

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f) Hydrostatic Testing of Extinguishers: To test strength of cylinders as wellas detect any leakages in the cylinder.

g) Record Keeping Purposes for Fire Extinguisher Maintenance Schedule

• Necessary to ensure that everything is inorder.

• Maintenance records should include thefollowing: Maintenance date and name of

person/agency carrying outmaintenance schedule;

Date of last recharge and name ofperson/agency performing therecharge;

Hydrostatic re-test day and name ofperson/agency performing thehydrostatic test;

Date of next recharge.

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5.3.2 Hose Reelsi. High pressure hose, connected to a constant

water supply (e.g Booster pump system,localized plumbing water supply, etc);

ii. Consists of rubber hose and nozzle attached todrum;

iii. Drum may be mounted on wall, or portabletype designed to be connected to water supply.

Portable Hose Reel Wall Mounted Hose Reel Parts

Wall Mounted Hose Reel

iv. Inspection of Fire Hose Reels: Typically once a month or as per legalrequirements; To ensure they are free from leakage, especially valves, nozzles and

rubber hose reels; Nozzles should be able to function as per design: Typical nozzles can

be tuned for jet streams or cone sprays; Check connecting booster pump systems (if any) for signs of

malfunction or leakages; Testing of hose reel to ensure that it should be able to discharge water

at a rate of 0.4 Liters/Second; Ensure accessibility of hose reels (not obstructed).

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5.3.3 Dry Riser Mains

i. Used for medium heightbuildings (In Singapore, itis between 25m – 60m).

ii. Main vertical pipe risingto upper levels of buildingfor use by fire fighters tosuppress fire.

iii. Pipes are dry. In theevent of fire, water mustbe pumped into thesystem before it can beused.

iv. Parts of a Dry Riser System:a) Breeching Inlet: Water is

pumped into the breeching inletfrom a water source, e.g Hydrantor fire truck;

b) Riser Pipe: Main pipe directingwater to the respective floors;

c) Landing Valve: Each level of the building has one

landing valve; In the event of fire, fire hose is

attached to the landing valve toallow firemen to suppress fire;

d) Air release valve: For releasingtrapped air in water supply whichmay cause air lock and hamperfire fighting.

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v. Maintenance: Visual Inspection; Hydrostatic Testing.a) Visual Inspection:

b) Hydrostatic Testing

Hydrostatic Testing: Changing Dry Riser System to 200 PSI 0r 13.8 bar viaBreeching Inlet

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5.3.4 Wet Rising Mains

i. Used for high rise buildings (ForSingapore, the definition is more than60m);

ii. Similar in design to dry rising main,except that the piping is connected toa water supply system and supplied bya constant water main;

iii. Pipes are wet. In the event of fire, firefighters can proceed to the location offire and connect the hose reel directlyto fight fire without the need to pumpwater from ground level;

iv. If water supply is insufficient or nowater supply from the utility services,a breeching inlet for fire service isconnected to the water tank for fireservices to supply auxiliary water intothe system.

v. Maintenance: Visual Inspection of Wet Riser System; Flow test; Pressure test; Testing of Pumping Equipment; Checking of Water Supply and Storage.

Pump room of Wet Riser System

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a) Visual Inspection:

b) Flow Test:• Tested for sufficient flow under gravity and pump operations;• Higher flow rates for commercial/non-residential buildings;• Usually governed by Code of Practice.• CP 29 (Singapore Code of Practice):

c) Pressure Test:

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d) Testing of Pumping Equipment

e) Water Supply and Storage

5.3.5 Fire Hydrants

i. Usually installed outside a building or at theground floor of the building.

ii. Connected to a municipal/localized watersource.

iii. Provides an instant water supply for firefighters to plug into with a fire hose viacoupling system and suppress fireinstantaneously.

Male coupling of fire hose

Fire Hydrant

Female couplingof Fire Hydrant

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iv. How it works:a) Rigging up fire hose male coupling to hydrant’s female coupling;b) Hydrant gate valve box chamber cover is removed;c) Using of hydrant key to turn on hydrant gate valve. Hydrant valve is used

to turn on and off water but not to adjust water flow;d) Hose reel nozzle is used to control flow rate to suppress fire.

Fire Hydrant key

v. Maintenance:a) Inspection should be carried out once a

year by qualified persons;b) Check for: Any obstruction to fire hydrant

(Remove, if any); Fire hydrant gate valve should be in

“open position” at all times. If not, usethe hydrant key to open valve;

Check for adequate flow rate andpressure.

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5.4 Automatic Fire Fighting Systemsi. Definition of Automatic Fire Fighting System: The ability of the system

to control and suppress fire without human intervention.ii. Automatic fire fighting systems must have the ability to:

– Detect;– Actuate extinguishing medium;– Deliver extinguishing medium to suppress fire.

iii. Types of automatic fire fighting systems: Water sprinkler system; Water spray system; Foam system; Halon System; Carbon Dioxide System; Dry Chemical System.

5.4.1 Water Sprinkler System

i. Definition: Thermal Sensitive Devices; Designed to release water when pre-

determined temperature is reached.ii. Advantages of Water Sprinkler System: Gives advanced warning or alert to fire; Provides early/first line of response to fire; Provides cooling (removal of heat) and

reduces smoke at the scene of fire; Reduces potential damage to property in the

event of fire; Reduces interruption to activities caused by

uncontrolled fire; Causes less considerable damage compared

to other manual water systems, such as firehose reels.

Fire Sprinkler

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iii. Types of Water Sprinkler Systemsa) Wet Pipe Sprinkler System:How it Works:Water piping system is constantly filled with water;When surrounding temperature reaches a pre-determined

temperature, sprinkler is activated and water bursts from sprinklerto put out fire.

Used for:Used for normal conditions with no special requirements, e.g

commercial offices, shopping centres, etc.Not suitable for premises which are undergoing extremely low

temperatures, e.g freezers, as water in pipe may freeze and burst.

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b) Dry Pipe Sprinkler Systems:How it Works:Sprinklers attached to pipeline filled with compressed air (Usually

Nitrogen;When surrounding temperature reaches a pre-determined

temperature, sprinkler is activated and air is released from thesprinkler;Sudden drop in pressure activates the dry pipe valve and releases

water into the dry piping system;Used for:Extremely cold conditions, e.g in a chiller room, where water pipe

systems are unsuitable due to the problem of freezing.

Combined Dry Riser and Wet Riser Sprinkler System

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c) Pre-Action Sprinkler System:Similar to the Dry Sprinkler System;Air fills up dry pipe system. May or may not be pressured air;Fire detection by fire detection system.

How it Works:When fire is started, fire detection system first detects the fire;Water Control Valve is opened, water is released into dry pipe;Fire Alarm is triggered;Sprinkler does not open until fire reaches its predetermined

temperature (higher than the one set for the fire detection system).Advantages:Can be used for extremely cold conditions due to the dry piping

system used;Use for fire detection system, not sprinkler, to release water. Hence

water is released faster than dry piping system;Because water is released faster, there is potentially less damage to

property.

Preaction Sprinkler System

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d) Deluge Sprinkler System: Similar to Pre-action system,

except that sprinklers arepermanently open;

In the event of fire, water isimmediately released via controlvalve into the dry pipe andstraight to the scene of fire viathe open sprinklers;

Used for high hazard areas, e.gfuel storage warehouses.

5.4.2 Water Spray System

i. Definition: Fixed piped water system connected to a consistent watersupply to provide fire protection with water via a series of nozzles overprotected area;

ii. Similar to sprinkler systems. May be used in tandem with sprinklersystems, but are generally not used to replaced sprinkler systems.

iii. Used for: Specialized protection for problematic areas, e.g fuel storage; Providing optimal fire protection and extinguishment.

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5.4.3 Foam System

i. Production of Foam:a) Proportioning Process: Correct mixture of foam agent, air and water;b) Foam Generation Phase: Generation of foam;c) Distribution Method: Distribution of foam for storage or fire fighting

purposes.ii. Types of Foam

Systems:a) Fixed Foam

Systems;b) Semi-fixed Foam

Systems.

iii. Fixed Foam Systems

Complete installations; Used to protect fixed

installations, e.g fueldumps.

Foam is dischargedthrough fixed outletsshould the system beactivated.

Schematic Drawing of Fixed Foam SystemsActivation of Fixed FoamSystem

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iv. Semi-Fixed Foam System

How it Works: Similar to fixed foam system; Discharged foam outlet can be

linked to mobile vehicle, usually afire truck;

Water supply from hydrant can belinked to fire truck;

Foam and water is mixed to allowfire truck to discharge foammixture on fire.

Suitable for: Fuel storage facilitiesstored over a large area, so much sothat fixed foam system installation isimpractical.

Linking up of fire truck to Semi-fixedFoam System

Discharging of Foam from a FireTruck

5.4.4 Dry Powder System

i. Consists of: Dry chemical Supply; Fixed Piping; Actuating mechanism.

ii. Types of Systems: Total Flooding System; Local Application System.

iii. Total Flooding System: Entire protected area is covered; Only when protected area is totally enclosed and no re-ignition expected; Pre-determined amount of dry powder is released if system is actuated by fire.

iv. Local Application System: Nozzle is directly pointed to fire localized protection only); Only when protected area is totally enclosed and no re-ignition expected; Pre-determined amount of dry powder is released if system is actuated by fire.

Localized Dry Powder System forKitchen

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Total Flooding System using Dry Powder

5.4.5 Halon System

i. Consist of: Halon supply (Usually in

cylinders); Linked to existing fire alarm

system; Halon Cylinders are connected via

piping network to variouslocations designated forprotection.

ii. Types of Systems: Total Flooding System; Local Application System.

Release of Halon Gas viaHalon System

Halon cylinders stored insecured location

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iii. Total Flooding System Used to protect

enclosed locations; Cannot be used in

places with high humanconcentration due totoxicity;

Halon 1301 used due tohigher volatility andlower toxicity.

iv. Localized ApplicationSystem Used to protect

enclosed locations oversmaller area;

Use of Halon 1211 forlower volatility.

Total Flooding System

5.4.6 FM 200i. Usually seen as an alternative to

Halon system: Lower toxicity; Not harmful to ozone layer; No harmful residues left behind; Suitable for use where there is

sensitive equipment, e.g Serverrooms.

ii. How it works: When fire activates fire

suppression panel, FM200 isreleased to the nozzle;

Additional nitrogen fromnitrogen cylinder is also releasedunder high pressure to createsupersaturated mixture for firesuppression.

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i. Total Flooding System Used to protect enclosed

locations; Quantity of CO2 must be

calculated based onvolume of protectedspace and concentrationof CO2 required toextinguish fire ofcombustible materials;

ii. Localized ApplicationSystem Used to protect enclosed

locations over smallerarea;

Nozzle pointed directly atlocalized point ofprotected space.

5.4.7 CO2 System

5.5 Fire Detection and Alarm Systems

i. Definition: System designed to detect the presence of fire

by monitoring environmental changes associatedwith combustion.

ii. When fire is detected: Fire Alarm is sounded to warn occupants of

impending fire for evacuation purposes; Automatic fire suppression methods (E.g FM

200) is activated; Designated fire lifts homed to ground level for

use by fire fighting teams; Location of fire source can be identified by

system to guide in-house fire fighting team andsubsequently the fire fighters;

Firefighters from nearest fire fighting precinctcan be activated.

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5.5.1 Fire Alarm Components

i. Fire Alarm Panel Central processing unit of the system. May

be linked to sub panels at various floors atmultiple storey buildings;

Receives signal from manual call pointsand respective automatic detectors andrelays it to output devices (Auxillaryequipment, alarm, decam);

Must have separate emergency powersupply (Emergency Battery OperatingSupply, or EBOPs) inside panel to provideE-power to alarm system in the event ofpower failure;

Addressable systems: Providesinformation on: Origins of fire alarm; Which device has been activated; What type of signal is being

transmitted. Non-Addressable Systems: Older type.

Provides information only on the zonewhere the signal is being received.

Fire Alarm Panel

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ii. Automatic Detectors Primary Function: Detect environmental changes, e.g Smoke in the

atmosphere, and send signal to fire panel; Usually mounted at ceiling surfaces or in air ducts; Activated by one or combination of the following conditions:

Fire Detection can be classified as follows: Spot detector: Detection of fire at one point; Line Detector: Detect fire along a continuous line of path.

Smoke Detector

Types of Detectors:– Heat Detectors;– Smoke Detectors;– Flame Detectors;– Aspirating Detectors.

Detector Types and their RespectiveCharacteristics

a) Heat Detectors: Spot detectors; Comes in two prototypes: Fixed Temperature:

Activates only whensurrounding temperaturereaches predeterminedtemperature; Rate of Rise: Activates

when there is a suddentemperature flux (Notsuitable for environmentswhere temperaturechanges are frequent). Heat Detector

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b) Smoke Detectors Three main types: Light scattering; Light Obscuring; Ionization.

Suitable for confined areas where combustible materials produce smallsmoke particles are expected in the event of fire;

Not suitable for locations where smoke is constant, e.g Basement CarParks.

1. Light Scattering SmokeDetectors:

Spot detectors;Operating principle:Dependent on detectinglight scattered by smokeparticles onto photocell. How Light Scattering Smoke Detector Works

Smoke Detector

2. Light Obscuring Smoke Detectors: Line Detector; Operating Principle: Light source projected to photocell; When smoke particles enter the

smoke detector, light reachingphotocell is interrupted;

Signal is sent out from detector. Suitable for high ceiling areas, e.g

Atriums.3. Ionization Detectors: Spot Detectors; Operating Principle: Two electrodes charging air inside

detector (+ve and –ve charges); Current flow caused by charge; Smoke particles entering detector

attracts electrodes, reducingcurrent flow. Once current dropsbelow acceptable alarm, signal issent out from detector.

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c) Flame Detectors Detects specific portions of flame:

Visible and invisible light spectrums; Typically infra red and ultraviolet lights

from the flame of the fire: 5 – 15 HertzHz lights are typically identified;

Extremely sensitive, used only for highhazard areas, e.g aircraft hangars,petroleum storage facilities, etc;

Infra Red FlameDetector

d) Aspiring (Air Sampling) Detector Uses a pump to draw air into unit; Drawn air is sent to lab to test for

combustion products.

iii. Fire Alarm Devices Two types:

• Audible Alarm Sounders;• Visual Signaling Devices.

To warn occupants of impending fire so as toallow for orderly evacuation of premises.

a) Audible Alarm Sounders:Generate continuous tone of alarm bell;Should be min. 5 dB (Decibels) over

ambient noise (Standard ambient noise is60dB);Should not exceed 120dB;All alarm bells in building should activate

simultaneously, unless it is a multi-stagealarm system.

b) Visual Signaling Devices:Used in facilities where ambient noise

makes alarm sounders ineffective;Additional strobe lights/signaling devices

used in conjunction with standard alarmsounders to reinforce announcement.

Audible Alarm Sounder

Visual Signaling Devicesc/w Audible Alarm

Sounders

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iv. Manual Call Points

Installed for use by occupants to sound emergencyalarm should fire or an emergency be detected.Signal is sent to the fire alarm panel;

Usually used as secondary back up to automaticdetectors, or in locations where detectors are notinstalled;

Manual call points should be free from obstruction. Types available: Break Glass Type: Activation by breaking the

glass. This will trigger a switch which thensends signal to fire alarm panel. Glass panelmust then be replaced to shut off signal; “T-Bar” Type: Activation by pulling down the T-

bar. This action triggers a switch which thensends signal to fire alarm panel. Reactivationcan be done using specialized key.

Break Glass ManualCall Point

T-Bar Manual Call Point

i. False Alarms Defined as the unintended activation of alarm

devices when there is no actual fire. Inconvenience to building occupants, as well as

creating a hazard. If actual fire occurs, occupantsmay take it for granted that it is another falsealarm.

Possible causes include:

5.5.2 Common Problems Associated with Fire AlarmSystems

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ii. Loss of Effectiveness in Fire Alarm Systems When fire alarm panels lose effectiveness, they

may not be able to warn occupants of fire; May be caused by:

i. Voice communication systems (VCS) are installedin buildings which are designated to have a FireCommand Centre (FCC) by law.

ii. The VCS is designed for the following functions:– Allows for communication between occupants

or fire fighting members at the scene ofincident and the FCC. This allows fire fighters atthe FCC to determine the extent of theemergency;

– Early communication allows for FCC team tostrategize and plan for the best strategy totackle emergency and deploy sufficientmanpower to tackle emergency promptly;

– Broadcasting via speakers allows FCC team toevacuate occupants promptly once the incidentis ascertained.

iii. Two types of VCS (VCS equipment should be fire-rated):– One-way communication system;– Two-way communication system.

5.6 Voice Communication Systems

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a) 1-way Communication System: Basically a network of loudspeakers to

provide a one-way communication fromFCC to occupants; Speakers are typically located in major

areas of access by occupants or membersof publics, such as lifts, lift lobbies,staircases, as well as emergency locationssuch as escape staircases, places of refuge,etc. Consists of:Microphone at FCC;Selector switches allowing for FCC to

switch off alarm when announcementis made;Amplifier: Sends signal to FCC indicator

board with regards to which speakershave been activated;Loud speakers at various strategic

locations for broadcasting purposes.

Microphone andSelector Switches in FCC

Loudspeaker

b) 2-way Communication System: Basically a network of telephone sets to provide a

one-way communication between FCC andoccupants; Telephone set at FCC should be linked to all telephone

sets for 2-way communications; Besides FCC, telephone sets should be placed at

equipment laden areas, such as lift motor rooms, lifts,AHU rooms, etc, as well as places of refuge or otherhigh risk locations. Consists of:Telephone sets at FCC;Selector switches allowing for FCC to switch of

alarm when announcement is made;Amplifier: Sends signal to FCC indicator board

once telephone is activated to indicate locationof activation;Telephone sets at various strategic locations May

be housed in secure lock boxes if vandalism is aproblem.

VCS Telephone Set

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5.7 Smoke Control Systems Definition of Smoke: By-products of combustion in rising plume of hot air; Can be in gaseous or solid particles; Consist of burned and unburned portions of fuel, plus

other chemical components released from combustedmaterial.

Why smoke is dangerous: Most deaths during fires are caused by smoke inhalation. Few people actually

burn to death; Smoke reduces visibility, hence impeding escape;

When designing fire installations, it should be assumed that all forms of smokefrom fires are dangerous, and should be directed away safely from building in theevent of a fire.Smoke Control within building proper is to achieve the following objectives: Keep smoke away from designated escape routes; Limit the spread of smoke throughout the building.

Methods of Smoke Control: Pressurization (Containment of smoke); Venting (Removal of smoke); Smoke Curtain.

5.7.1 Pressurization

i. Pressurization of escape stairways/routes: To prevent smoke from entering escape route when access door is opened; Achieved by keeping the escape route area constantly pressurized by air; Activated by alarm system during fire.

ii. How it works:

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iii. Use of air-pressurized escape routes mandated by regulations:In Singapore, pressurization is provided for the following: Medium to high rise buildings (Exceeding 24m); Internal exit staircases with no other forms of natural ventilation; Basement staircases (More than 4 storeys).

iv. Pressurization Level:

v. Air Velocity: Maintain at 1.0 m/s when activated(Escape doors opened orclosed).

vi. Equipment: Each ventilation system is complete with mechanical ventilation fan , ducting

and other Mechanical ventilation accessories; Each ventilation system for each staircase, independent of one another.

5.7.2 Venting

i. Venting: Direct, method of directing smoke toexternal environment.

ii. Nature of smoke progression: Smoke tends to rise to the highest point within the

building (Ceiling, atrium, etc); As smoke builds up, it gets lower and lower,

eventually engulfing whole building and creatinghazard for occupants to escape.

iii. Purpose of Venting: Give sufficient time for occupants to evacuate

building; Give sufficient time for fire fighting team to locate

fire and extinguish it without being obscured bysmoke.

Extract smoke to prevent dangerous build up ofsmoke within building premises.

iv. Types of Venting: Natural ventilation; Mechanical Ventilation.

Mechanical SmokeControl Fan

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v. Technical Specifications for Vent Systems

Venting via Natural Ventilation Venting via Mechanical Ventilation

5.7.3 Smoke Curtainsi. Use for large buildings, such as shopping complexes.ii. Purpose: To prevent smoke from spreading sideways.iii. Designed to work with venting system: Creates smoke reservoir for

smoke to be directed out of building via venting system.iv. Designed to be fire rated (Min. as good as the roof structure).

Smoke Curtain in Shopping ComplexSmoke Curtain being ManuallyActivated for Testing Purposes

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5.7.4 Fire Dampers

i. Fire dampers: Passive fire protectiondevice installed inside HVAC and ACMVducts to prevent smoke fromspreading inside duct works;

ii. Fire damper must be fire rated (Usuallysimilar to the surrounding wall whichits ducting penetrates).

iii. How it Works: When fire occurs, thermal element

melts (i.e the fusible link), droppingthe fire rated door in the damper;

Another design would be to connectthe damper to the fire alarm totrigger the fire damper, instead of thethermal element.

When the door drops, smoke isprevented from spreading.

How the fire damper works

i. In the event of fires, designated fire lifts are designed to function the followingroles, even if the main power supply is cut:

– Ensure that the internal lift lighting and ventilation systems are working viaEmergency Battery-Operated Supply (EBOPs);

– The lift is able to function, so that it can still transport passengers and at thesame time home in to ground floor for use by fire fighters. This is achievedusing generator and/or battery power;

– In the event the building has no generator supply (For buildings which arelower than 60m), the lift is actually homed to the nearest floor. This isachieved by a separate battery operated system known as Automatic RescueDevice (ARD).

ii. Firemen can manually activate and control lifts via firemen switch (These areusually locked to avoid vandalism, with firemen or authorized crew with thekeys to manually control the fire lifts).

5.8 Fire Lifts

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i. Emergency lighting: Placed in strategic locations to direct occupants tothe nearest exits in the event of an emergency by providing luminance,particularly when normal lighting has failed due to power failure.

ii. Exit signs help to provide instructions to the nearest exit, while otheremergency lights help to provide luminance for evacuation purposes.

iii. During normal operations, emergency lights are connected to theemergency switch board or, in the case of ARD, normal switchboardpower supply;

iv. During a power failure, these emergency lights have their own batterypacks to last a prescribed duration until power resumes, and/or to giveample time for occupants to evacuate building.

v. Exit and emergency lights are designed such that even in a smoke-filledenvironment, they can still be highly visible.

5.8 Emergency & Exit Lights

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Illustration showing Exit Lighting and EmergencyLighting Placements in a building proper

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Tutorial Questions:1) Basics of Fire Science:i. Define “fire”, and identify the by products of fire (4 marks).ii. With the aid of a diagram, indicate the basic elements of fire (4 marks).iii. Identify the classes of fire and indicate the types of fire which these classes

denote. Give 1 example for each class of fire (8 marks).iv. Explain the methods whereby fire can be extinguished (4 marks).

2) Dry and Wet Riser Mains are used by fire fighting teams to fight fires in multi-storey buildings.

i. Indicate the height prescription for the installation of dry and wet riser mains(2marks).

ii. Indicate the key difference between a wet riser system and a dry riser system (2marks).

iii. Describe the components of a dry riser main system and explain how it can beused by fire fighting teams in the event of an emergency (8 marks).

iv. Describe how hydrostatic testing is carried out on the dry riser system and statethe criteria for compliance (4 marks).

v. Describe how the wet riser system can be used by fire fighting teams in the evenof an emergency (4 marks).

3) The fire alarm system is an integral feature in many buildings.i. Sketch/draw a simple schematic diagram of the fire alarm system (7 marks).ii. Briefly explain the how the fire alarm system works (5 marks);iii. Explain why false fire alarms can be detrimental to occupants in the building,

and list down the possible causes of false fire alarms (8 marks).

4) In the event of a fire, smoke is considered to be the most dangerous killer.i. Briefly describe the nature of smoke and its contents (3 marks).ii. List down the ways smoke can kill in the event of a fire (2 marks).iii. List down the objectives of smoke control techniques (2 marks).iv. List down three methods of smoke control (3 marks).v. Discuss the use of fire dampers in air ducting systems, including the

requirement(s) of fire dampers and how it works (10 marks).