L2 Fire
Alarm
IS 2189 :
2008: Indian Standard. Selection, Installation And. Maintenance Of
Automatic Fire. Detection And Alarm System
IS 11360
(1985): Specification For Smoke Detectors For Use In Automatic Electrical Fire
Alarm System [CED 22: Fire Fighting]
A fire
alarm system is number of devices working together to detect and alert people
through visual and audio appliances when smoke/fire is
present. These alarms may be activated from Smoke Detectors, Heat Detectors, MCP etc.
Smoke
detectors do not have a listed spacing. They have a recommended spacing of 30
feet between detectors. However, smoke detectors can be installed up to 41
feet apart in corridors up to 10 feet wide. The main fact to remember is that all
points on the ceiling must be within 21 feet of the detector.
Commercial
systems are categorized as follows (All include manual call points):
·
L1
– Detection provided throughout the entire premises
·
L3
– Detection provided on all escape routes and adjoining areas
· L3/L2
– Detection provided on all escape routes and adjoining areas, as well as
additional detection in specified high risk areas
·
L4
– Detection provided on all escape routes only
· L4/L2
– Detection provided on all escape routes and additional detection in specified
high risk areas
When
a system is installed in a premises where there is more than one interlinked
system in operation, then the suffix “X” is used.
Many
fire authorities are now insisting on specific standards of fire alarm systems
within buildings. These categories are defined in the recommendations of
BS5839. One of the most common categories which is being asked for is a
BS5839 category L2 Fire Alarm System. The prefix 'L' for the category
type stands for life protection. This means that the primary purpose of a
category L2 Fire Alarm is to protect life. Whereas BS5839 system designs
with a 'P' prefix are primarily designed to protect damage to property.
L2 Fire
Alarm Systems are designed to offer automatic detection on all escape
routes within a building, with the addition of all rooms adjoining to the
escape route. An L2 Fire Alarm design should also take into account any
further areas of high risk which may not necessarily be covered with detection
on the escape routes and adjoining rooms. Examples of these areas could
be boiler rooms, plant rooms and other areas with heavy plant machinery (such
as in roof voids).
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An Example of an L2
Fire Alarm Design
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L2
Fire Alarm designs should also incorporate audible sounders throughout the
building which operate when the fire alarm system is activated. These
sounders should achieve a minimum sound pressure of 65 dB (A) throughout
the building and a minimum of 75 dB (A) at the bedhead where there people
sleeping within the building.
An
L2 Fire Alarm should also include manual call points on all exits to open air,
and in buildings above a single storey all entrances to stairwells on the
floors above the ground floor. In large buildings it should also be noted
that nobody should have to travel for more than 35 metres to reach a call
point. This means that further call points may be needed to be positioned
within the property to achieve this. Call points may also need to be
positioned in high risk areas. One example of this may be a paint booth
where high flammable substances are present. A call point may need to be
positioned in close proximity to enable an alarm to be raised quicker should an
incident occur.
Awareness
of the system user is also essential, less able bodied people may or may not be
capable of exiting without assistance, but high levels of people with sporting
injuries or with hearing difficulties may require a system which addresses
their needs.