Module 14 Flashcards
what is the BS for fire alarms?
BS 5839-1 : 2013
define AFD?
.. Automatic fire detection and fire alarm System (other than a single self-contained smoke or fire alarm) in which an alarm of fire can be initiated automatically
AFD can be classed as the following? 2 systems?
a) two-state fire detection systems: fire detection and fire alarm systems that are capable of indicating only two output states, namely ‘normal’ or ‘fire’ conditions;
b) analogue fire detection systems: automatic fire detection and fire alarm systems in which a signal representing the value of the sensed phenomenon is processed and represents ‘normal’, ‘fire’ and at least one other abnormal condition.
define manual system ?
Manual system
System containing no automatic detectors and in which an alarm of fire can only be initiated manually
AFD vs Manual
Manual
Manual fire detection and fire alarm systems are often sufficient to satisfy legislation in workplaces in which no one sleeps
Automatic fire detection is usually required by legislation to supplement the manual system in premises in which people sleep.
AFD may be necessary to satisfy legal requirements under the following circumstances?
.. where the automatic fire detection forms part of a fire engineering solution
b) where fire protection systems, such as door closing facilities or smoke control systems, are to be operated automatically in the event of fire
c) where the low level of occupancy of a building, or part of a building, is such as to create the potential for fire to prejudice means of escape by occupants before they are aware of the fire.
considerations to determine what alarm should be installed?
.. Is the fire detection and warning system appropriate to the risk?
•Considerations:
−What is the risk?
−Life or property?
how to determine what AFD is required?
.. Extent of automatic fire detection should be determined by a fire risk assessment
- The factors affecting choice of detection technique are speed of detection, nature of combustibles, rate of fire growth, etc
- Is there adequate coverage by system components?
- Does every space need a detector/call point/sounder?
Categories defined by objective rather than coverage
•Five categories of life protection, two of property protection plus manual.
define L system?
Category L Systems
Category L Systems are automatic fire detection systems intended for the protection of life. They are further subdivided into L1 to L5
define L 1-5 AFD systems?
.. Category L5
The location of detectors is designed to satisfy a specific fire safety objective (such as to protect the occupants of an inner room).
L4
Detectors installed within those parts of the escape routes comprising circulation areas and circulation spaces, such as corridors and stairways
The objective of a category L4 system is to enhance the safety of occupants by providing warning of smoke within escape routes.
Category L3
Detectors installed within escape routes and in rooms which open onto escape routes
The objective of a category L3 system is to give a warning of fire at an early enough stage to enable all occupants, other than possibly in the room of fire origin to escape safely, before the escape routes are impassable owing to the presence fire, smoke or toxic gases.
Category L2
A system identical to an L3 system, with the additional objective of affording early warning of fire in specified areas of high fire hazard.
Category L1
Systems installed throughout all areas of the building
The objective of the L1 system is to offer the earliest possible warning of fire, so as to achieve the longest possible time for escape.
define P system?
Category P Systems
Automatic fire detection and alarm systems intended for the protection of property. These are subdivided into Categories P1 and P2.
Define P 1 system
.. Category P1
Detectors installed throughout all areas of the building
The objective of a category P1 system is to offer the earliest possible warning of fire, so as to minimise the time between ignition and the arrival of fire fighters.
define p 2 system
.. Category P2
Detectors installed in only defined parts of the building.
The objective of the P2 system is to provide early warning of fire in areas of high fire hazard or areas in which the risk to property or business continuity from fire is high.
detection zone requirements
If the building is less than 300m² a zone may cover more than one floor
•Single zone should be no bigger than 2000m²
•Search distance should not exceed 60m
•Large uncompartmented warehouses should not exceed 10,000m².
sounder level requirements ?
.. Generally 65 dB(A) •May be reduced to 60 dB in: −Stairways −Enclosures less than 60m² −Specific points of limited extent.
Where background sound is over 60dB(A) the alarm should be 5dB above background noise
•Sleeping accommodation 75dB(A) at the bedhead
•Maximum sound 120dB
•Do not mix bells & sounders.
when are visual alarms required?
.. Provided if noise levels are likely to exceed 90dB(A)
- In readily visible locations
- Flash rate between 30 – 130 flashes per minute
- Different to other visual signals
- Multiple unsynchronised signals can cause seizures
- Sufficient to attract attention.
alarms for hearing impaired?
Alarms For Hearing Impaired People
•Can be fixed or portable
•Visual or tactile device (can be pager, vibrating pillow pad or visual alarm)
•Normally radio linked.
manual call point requirements
.. Manual Call Points •All call points identical •At all final exits •At storey exits (not in the stairwell) •Max 45m travel •Travel distance reduced to 25m if: −Limited mobility −Rapid fire development.
. 1.4m above floor, less if wheelchair users
•Surface mounted or recessed showing at least 15mm
•If casual or malicious operation use hinged cover (variation).
4 types of detector ?
Heat
Smoke
Combustion Gas ( CO Doctor)
Infrared or ultraviolet ( flame Detectors)
requirements of heat detectors?
.. Fixed temperature
•Rate of rise
•Or mixture of above
•Comply to BS EN 54-5.
requirements of smoke detectors ?
.. Point type detectors −Ionisation (current flow in chamber) −Optical (light scatter) •Video surveillance, analysed electronically (no product standard exists to define performance) •Optical beam detectors •Aspirating systems.
requirements of combustion gas detectors ?
.. Detects carbon monoxide
•Due to diffusion of the gas through certain forms of construction detectors could operate some considerable distance away (giving misleading information)
•Sensors have a finite life.
flame detectors
.. Use infrared/ultraviolet radiation
•Wavelengths that ozone layer filters out from the sun.
multi - sensor detector definition?
.. Use more than one sensor
•Enhance performance and reduces false alarms
•Could be heat during the day, smoke at night, using a timer.
