Design Principles of Fire Detection and Alarm Systems for Buildings

8/13/2019 Design Principles of Fire Detection and Alarm Systems for Buildings

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COURSE TARGET

Dates of changes

Life and Property Categories

Design process Manual call points

Detectors area of coverage

Sounders and noise levels

Zone size

Technology of system components

Cable requirements

Standby supply

False alarm management

The role of the Responsible Person.


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Some standards updates

BS5839 pt1 1988

WAS WITHDRAWN ON 15 JULY 2003

FROM 15/7/2003.

ALL SERVICING, DESIGNS AND INSTALLATIONS

WILL BE TO THE NEW BS 5839-pt1,-8,:2002


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Why has the standard been updated?

The current edition of BS 5839 part 1 was written in 1988. Since thenthere have been:

Changes in technology

Changes in custom and practise

The new standard takes the above into account as well asrecommendations found in the European standard BS EN 54, 1-14.


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Categories of Life and Property Systems

M - Manual call points L5 - (could follow a risk assessment).

L4 - Principle escape routes

L3 - Escape routes and areas leading onto escape routes

L2 - Defined areas (Hazards / areas of high risk)

L1 All areas

P1 - System installed in all areas of the building few sounders

P1M - As P1 but with sounders throughout

P2 - System installed in defined parts of the building few sounders.

P2M - As P2 but with sounders throughout.


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Consultation

Consult the fire authorities Special risks, uncertainties

E.g. connection to remote manned centre, delays etc

Input from interested parties: Building control officers

Insurers / owners

Consultant / architect

Occupiers

Service contractor

Property

and or life

protection


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BS5839 PT 1 2002 Fire Alarm Design

The process of designing a system is to define the following Detection zones

Communication with the fire brigade

Audible / Visual alarm signals

DDA Staged alarms

Manual call point locations

Types of detectors

Location of detection and area of coverage Considerations to design out False Alarms

Control and indicating equipment

Network systems

Power supplies Interfacing to plant lift shutdown, Air Con, etc

Electrical safety

User responsibility and customer training.


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MANUAL CALL POINTS

Breaking frangible element operates switch Located so clearly visible, on the way out

All the call points must be similar

do not mix hammer and thumb push types

Use plastic element (not glass) in food prep areas If necessary, use drip proof, waterproof or hazardous area types

Some shops do not have public call points


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Call points (sec 20.2c)

MCPs should be sited at all exits to the open air regardless of it being adesignated Fire Exit or not.

1 - 4 story high, accommodation blocks, MCPs sited on landing or stairs

adjacent to landing.

In buildings with multi-stories / and or phased evacuations, MCPs should

not be sited on stairways, therefore site MCP's on landing to stairs only.


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SITING manual call points

Escape route 1st floor

Ground floor

Landing

Stairwell

Final exit to open air


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Choosing the point Detector

Heat: Few false alarms. Less sensitive than smoke detectors and not foruse on escape routes. Ideal for kitchens and boiler houses. The rate of

rise is the most sensitive.

Smoke, Ionisation: sensitive to initial stages of fire. (ionisation devices

being phased out)

Smoke, Optical: sensitive to larger particles from smouldering fires.

Immune to wind speed.

Combined optical and heat: can be as sensitive to initial fires as the

ionisation detector.


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Choosing the point detector

Kitchens fixed temperature is best RoR may be too sensitive

Loading bays lorry fumes may cause alarms overhead heaters may causealarms in cold weather, RoR should be used

Smoking rooms RoR should be used

Kitchens keep smoke detectors approx 7.5 mtr away from door.

Keep ionisation detectors away from high air flow fans = faults occur Optical smoke is best for most locations escape routes, open office areas

etc,

Flame detectors are good for generator / gas installations etc

But beware of welding and friendly flames will cause false alarms.


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COVERAGE for point detectors

Spacings specified in BS 5839 part 1 For detectors mounted on flat horizontal ceilings limits are based on:

100sq m for smoke detectors

50sq m for heat detectors

Any point in a room to a detector should be less than: 7.5m for smoke detectors

5.3m for heat detectors


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SMOKE DETECTOR: spacing

OPEN AREA

7.5m

10.6m5.3m

area

10.6 x 10.6= 112sq m

(approx. 100sq m)


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HEAT DETECTOR: spacing

OPEN AREA

area

7.5 x 7.5= 56.3sq m(approx. 50sq m)

5.3m

7.5m3.8m

Heat detection is not allowed in corridors

If they are used as escape routes, this is

due to smoke logging and travel / visual restrictions.


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SMOKE DETECTOR: spacing in narrow escape routes

CORRIDOR 2m WIDE

9m

2m

in room smoke detection on

ceiling or above door L3 ONLY

Sec.13.5.3.17.9m

Note: detectors should be onthe centre in this calculation


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DETECTORS: distance from ceiling

spreading

14 deg

Smoke detectors:

25mm min, 600mm max

Heat detectors:

25mm min, 150mm max

min

Ceiling / slab

Lintel / girder max

detector


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DETECTORS: near isolated obstructions

Detectors not less than

2 x depth of isolated

obstruction Example: luminaire

CCTV, Projector,

Emergency light.

ceiling

2XP

P

luminaire


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Sound Levels Sec 16.1-2

Generally sound pressure levels should be no less then 65 dB.

However at specific points of limited extent within any area, sound

pressure levels of 60 dB are acceptable.

Examples of such areas include:

Staircases, small enclosed spaces, cellular offices. Enclosure that are no more than approximately

60m in area.


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Sound loss over distance

100dB 94dB 88dB 82dB

1mtr 2mtr 4mtr 8mtr

Note 1. As you double the distance you loose 6 dB.

2. Sound levels differ in HTM 82 STANDARDS

= Hos itals, Nursin homes etc.


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ALARMS: sound levels. Sleeping risk

20dB(A)

30dB(A) = LOSS THROUGH FIRE DOOR

= LOSS THROUGH NORMAL DOOR

75dB(A)

85dB(A)

125dB(A) 95dB(A)

8 MT

3


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Z3

Z1

Z2

ZONE AREAS

2000sq m per zone - maximum

area

Generally, one zone limited toone storey

For small buildings less than

300sq m

can be all one zone

irrespective of storeys Total floor area 300sq m allone zone


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TECHNOLOGY : standard - non addressable

Z1

Z2

Z3

Conventionalpanel (P)

z1

z2

z3

TECHNOLOGY A l dd bl l


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TECHNOLOGY:Analogue addressable panel

I/F

654321

Addressablepanel

7 8 9 10 11 12I/F1314151618 17

I/F 19

Exact location of f ire, with options to alter the parameters of the detection

sensitivity, time delays. This system is more often specified for

complicated cause and effects for lifts, plant shut down etc.


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SITING the fire alarm panel

Availability to staff Away from unauthorised access/tampering

Availability to the fire brigade

Near to adequate lighting

In area of low fire risk

In a relatively quiet area.


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Cabling

STANDARD fire resistant cable should be used in buildings that

require single phased evacuation

(soft skin i.e.: FP200, Fire tuff.)

ENHANCED fire resistant cable should be used in buildings

requiring phased evacuation e.g. high rise buildings i.e.: (MICC).

Fix using metal clips or metal trays and trunking

Mechanical protection MICC or armoured self-protected

Protect other cables if vulnerable, below 2m height.

All cables linking manual call points detectors and

mains power to the control panel should be fire resistant cable.


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STANDBY BATTERIES

Category M and L

Standby period 24 hour +30 mins alarm load.

Category P Standby period 24 hour longer than the time the

building is unoccupied or a max of 72 hours which ever

is the less.


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False Alarm Managementand

USER RESPONSIBILITIESBS5839 pt1, 2002 sec3&7.


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CATEGORIES OF FALSE ALARM

Four False alarm categories:

1. Equipment false alarms

Faults in equipment

2. Unwanted alarms (equipment works perfectly) Fire-like phenomena, e.g. smoking, burning toast, hot work,

building work

3. Malicious false alarms

4. False alarms with good intent.


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ACCEPTABLE RATE OF FALSE ALARMS

Any false alarm is undesirable BS5839 Pt1 1988 rate now unacceptable

Complete elimination impossible

RP to monitor periodically & action to reduce Many factors may give rise to false alarm

Proportional to qty devices fitted, higher if mainly smokedetectors. Filtering may reduce

Manual & Heat detectors few false alarms

Possible future action by fire authority


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CAUSES OF FALSE ALARMS

fumes

steam

tobacco smoke;

dust

insects

aerosol spray

high air velocities

hot work bonfires

incense candles

electromagnetic interference

high humidity

water ingress

temperature changes

accidental damage


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MAINTENANCE and the LAW

Fire Precautions (Workplace) Regulations require a system of

maintenance

Systems with no battery backup are not legal

The service provider should advise users to replace urgently

Failure to keep the fire detection and alarms in good working order is acriminal offence

Arranging a suitable system of maintenance is so easy to do, thatneglecting to do it is blatant flouting of the law.


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The Health and Safety (signs & signals regulations) (1996)

This regulation requires that fire warning systems shall be provided with

a guaranteed emergency supply in the event of a power cut.

This means that systems not having standby power supply (battery back

up) are no longer legal.

This is also a law, failure to comply being an offence.

Ref clause 46.2.b.4 THE H&S.S.S REGS 1996.


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MAINTENANCE - Routine Testing Responsible Person

Routine testing and inspection user or RP

Weekly operate MCP

Occupants report any poor audibility

Different MCP each week, recorded in log book If 150 MCP, then 150 weeks for RP to test all

Monthly attention by user or RP

Generator if part of standby power supply

Visual inspection of vented battery

If RP is not trained for this Competent person monthly visit.


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MAINTENANCE - CP

Inspection and servicing

Periodic servicing - Competent Person 3 monthly inspect and top up vented cells

Periodic inspection based on risk assessment, may

be up to 6 months

Annual test now generally test all over a 12 month

period Maintenance Engineer to issue servicing certificate if

tests acceptable.


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USER RESPONSIBILITIES

Log book updated correctly

Check cie at least every 24 hours

Arrange for maintenance by CP

Train other occupants, fire alarm and procedures

Limit false alarms

MCP and detectors not obstructed

Action on any relevant changes in the building

Hold small quantity of spare parts Action following Pre Alarms


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Zero Maintenance the RISK

Risk of no maintenance

Eventually fire alarm

will stop working

Alarm may be delayed

- loss of life

Brigade may not be called

- Loss of property

Continual false alarms will

make people complacent

The fire alarm will give

false alarms

In a genuine emergency

People may not evacuate.

IF THE FIRE ALARM DOES NOT WORK,

THE PREMISES MAY NOT BE SAFE, AS A PLACE OF WORK


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Hazards of a zero maintenance fire alarm

Regular Recalibration of specialist gas type detectors, 5-15 years

External circuit fault may happen any time

Standby batteries life 4 years is normal

Contamination of devices from dirty / harsh environments

Damaged detectors undetected

Alterations to building may happen any time.


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Responsible persons duties

Supervise the system

Training of all users

Liaison with building engineers

Authorisation of work on the system

Ensuring detectors are unobstructed Clear access to control panel

Control of keys or access codes disks etc

Identify persistent false alarms details entered in log book

Identify any changes in working processes false alarm issues

Identify areas of risk for shutting down in a fire condition.


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Reducing automatic false alarms

Responsible person requires a permit to work for contractors

Contractors sign a book make a method statement including how they can

reduce false alarms

IE:- hot works, carpet cleaning, drilling, cutting bricks, plastering, paint

stripping, washing down etc

All the above helps avoid false alarms and real fires

Training for staff.


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Routine testing by the responsible person

Daily attention clause 47.2 user responsibilities

Check panel shows normal if not enter in log book action taken

Check lob book to ensure previous faults have been actioned

Weekly attention-

Activate one different MCP and confirm the sounder audibility and

operation results entered in the log book. No time limit if you have 50 MCPs then it will take 50 weeks.


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FILTERING OUT FALSE ALARMS

Activation of

single smoke det

False alarm found

And cancelled

Investigate delay

allows inspection

before automatically

transmitting the

signal to the ARC.

Coincedence detection

may be required toOverride the

investigation delay.

Seek and find

e.g. 5 mins *5 mins times out

Real fire

Operate MCP

Coincedence

Detector = override

EVACUATE

* ALWAYS CONSULT THE FIRE AUTHORITIES BEFOREINSTIGATING AN INVESTIGATION DELAY.

Schematic for design against false alarms


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g g

SELECT the AREA

Are the special measures acceptable

to the interested parties?

Are the special measures detrimental to

The system objectives ?

Is this frequency now acceptable ?

Formal proposals for further special

Measures to minimize false alarms or their effects

Identify likely frequency of false alarms

Identify means by which proposed system

will minimise false alarms

Identify circumstances, processes and actions with

Potential to cause false alarms

Consider proposed protection

For this area

Proceed to

Next area.

Is this frequency acceptable ?yes

no

yes

no

no

yes

no yes


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CERTIFICATION

In triplicate, all certs must signed by the person directly responsible

Design Certificate

Installation Certificate

Commissioning certificate

Acceptance Certificate

Verification certificate

(optional) Maintenance Certificate.


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SUMMARY

Designers Now have clearer recommendations from BS5839 on being

flexible to design out false alarms.

Installers more pragmatic - call points H = 1.4m+/-0.2m

Commissioning more knowledge / training

Service organisations details how to limit agreed quantities of false alarms.

LPC1014 / BAFE 203 third party accreditation or registered installers

Users legal obligation on user and guidance / employer for service.


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SUMMARY OF FALSE ALARM MANAGEMENT

Consultation with all parties

Appoint a responsible person - RP Supervise painting, decorating, hot work

Record and compensate for any change of use

Keep fire alarm logbook up to date

Agree an acceptable rate of false alarms (e.g. less

than 1 false alarm per 100 detectors per annum) in a

clean environment *** Ensure service and maintenance carried out

If no effort to limit system is not compliant

*** NOTE:- In a factory 1FA / 75 detectors is more realistic.40 or less detectors max 2 FAs PA is average.

L S


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Design Principles of Fire Detection and Alarm Systems for Buildings