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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WAS WITHDRAWN ON 15 JULY 2003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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THANK YOUANY QUESTIONS?