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System Design

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System Design

• Primary Detection

• Secondary Detection

• Standards

• Pipe Design

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Primary Detection

Where smoke will travel when air

conditioning is operating

• Air handling units

• Duct detection

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Primary Detection

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Primary Detection

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Secondary Detection

Where Smoke is likely to travel when air conditioning is

shut down or not installed

• Ceiling level detection

• In cabinet detection

• Void detection

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Secondary Detection

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Standards

• BS5839 Pt 1 CoP for Fire Alarm Systems in Buildings

• BS6266 CoP for Fire Protection for Electronic Data Processing installations

• BFPSA CoP for Category 1 Aspirating Detection Systems

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Siting Conventional Detectors toBS5839 Pt1 (Secondary Detection)

7.5m• Maximum size for fire zone is 2000m2

• Maximum area coverage per detector 100m2

• Grid overlay design concept gives spacing 5 m from walls - detector spacing 10m maximum

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Conventional Detector Layout (Secondary Detection) BS5839

5m 10m 10m 10m 10m 5m

5m

FIRE ZONE PLAN

10m

10m

10m

5m

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HSSD Layout (Secondary Detection) BS5839

Sample Holes

Sampling pipes

5m 10m

10m 10m 10m 5m

5m

FIRE ZONE PLAN

10m

10m

10m

5m

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Siting Conventional Detectors toBS6266 EDP Areas & High Airflow

Application Recommended coverage per detector Remarks and recommendationsEDP equipmentroom (ceilingheight about3m)

15 m sq. to 25 m sq. (see note) In the extreme case where theearliest possible warning of firein a cabinet is required, there isno substitute for detectors withinthe cabinet.

Without ventilation:20 m sq. to 30 m sq. (see note)

In false ceilings with beams thelower figure should be taken. Ifthe beams are deep so as tocompartmentalize the space, adetector should be fitted in eachsuch compartment

False floors,false ceilings

With Ventilation:(a) between 15 m sq. and 20 m sq. (see

note) for air velocities of 4 m sq. orless

(b) 10 m sq. for air velocities greater than 4 m/s

Tape stores Room protection, 10 m sq. to 30 m sq.(see note)

Electricaldistributionboards andemergencypower supplies

Room protection, 10 m sq. to 30 m sq.(see note)

In installations with enclosedemergency power cabinets,consideration should be given toproviding additional protectionby the installation of detectorsinside the cabinet.

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Siting Conventional Detectors toBS6266 EDP Areas & High Airflow

NOTE: Where the risk justifies the extra cost involved, or the maximum response to fire is required, or as ventilation rates increase, the area of coverage per detector should be reduced.However, under these circumstances, the higher area coverage may still be acceptable if the point - type smokedetectors are supplemented by a high sensitivityaspirating system that forms part of the fire alarm system.

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Siting Conventional Detectors toBS6266 EDP Areas & High Airflow

• Maximum size for fire zone is 500 to 750m2

• Maximum area cover per detector 25m2

• Grid overlay design concept gives 2.5 m from walls - detector spacing 5m maximum

5m

5m

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Conventional Detector Layout (Secondary Detection) BS6266

2.5m 5m 5m 5m 5m 2.5m

2.5m

FIRE ZONE PLAN

5m

5m

2.5m

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HSSD Layout (Secondary Detection) BS6266

Sampling pipes

FIRE ZONE PLAN

Sample Holes

2.5m

5m

5m

2.5m

2.5m 5m 5m 5m 5m 2.5m

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HSSD Duct samplingReturn air pipe

HARTDetector

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AIRTIGHT FITTING(EG. GROMMET)

2mm DIAMETER SAMPLING HOLES

SAMPLE TUBE

RETURN TUBE

AIRFLOWDetailed view of Duct pipework

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HSSD Air Handling Unit Sampling (primary)Samplingpipe

HARTDetector

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Sampling pipe centred on grilleEnd Cap

Grille

Distance from grille must be such that air velocity less than 6 m/s

Air Handling Unit Sampling

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Air Handling Unit

To HARTdetector

Samplingholes

Airflow out

False floor

Airflow in

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Air Handling Unit

Sampling holes

False floor

To HARTdetector

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Balanced sampling system

AHU Cabinets

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In Cabinet sampling

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In-cabinet Sampling from Underfloor Void

Equipment

cabinet

Sample tube can detect at different heights

Sample tube enters cabinet from underfloor trunk sampling pipe

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Sampling a Ventilated Equipment Rack

Sampling Pipe

Ventilation grille

Sampling points (Facing into airflow)

Equipment Rack

Airflow Direction