|
|
|
INITIAL CONSIDERATIONS |
|
Relevant Standards |
BS 5839 part 1 1988, is
the standard for Fire Detection and Alarm Systems in Buildings, this
standard is the code of practice for system design, installation and
servicing.
This publication is not intended to replace BS 5839 Part 1, copies of this
standard can be obtained from the customer services department at :-
British Standards Institution.
389 Chiswick
High Road, London
W4 4AL
It is
important that any installation engineer, or electrical contractor
undertaking this type of work is fully conversant with BS5839, which covers
systems from simple manual installations to fully automatic fire detection
systems. |
|
Application / Survey |
The importance of design
planning cannot be overstated. Many parties are likely to have an interest
in a fire detection and alarm system. Those who should be consulted before
the design is finalised may include:
-
The System Installer / Contractor
-
The Local Fire Authority (fire officer)
-
Consulting Engineers or Building Services Engineers
-
Architects and engineers
-
The Health and Safety Executive
-
The Building Control Officer
-
The Fire Insurer
The consideration
prior to design, which should also be detailed within the system
specifications, may include:
-
The purpose of the system
-
Typical Fire Service attendance time
-
Occupant escape times
-
Other actions to be taken in the event of a fire
-
Other occupants (particularly for multiple-occupancy)
-
Service and maintenance requirements
-
System operation requirements
Fire alarm systems
are installed for many different reasons, and purposes.
They may be installed
for the protection of life, or the protection of property, or a mixture of
both.
Most buildings that
are intended to be occupied with people, will need both life and property
protection to differing degrees.
There is a
classification of systems in BS 5839: Part 1: 1998, which is used in this
guide. |
|
Systems for
Protecting Property
(P) |
A satisfactory fire
alarm system for the protection of property will automatically detect a fire
at an early stage, indicate its location and raise an effective alarm in
time to summon the fire-fighting forces (both resident staff and fire
brigade). |
|
|
Type P1 |
A system covering all
parts of the protected premises including voids over 800mm (8M) in height. |
|
|
Type P2 |
A
system covering only those parts of a premises having a Relative High fire
risk |
|
SYSTEMS FOR PROTECTING LIFE (L)
|
|
A
satisfactory fire alarm system for the protection of life can be relied upon
to sound a fire alarm while sufficient time remains for the occupants to
escape. |
| |
|
|
Type L1 |
A
system covering all parts of the protected premises including all voids over
800mm (8M) in height |
|
Type L2 |
A
system covering only those parts of a building where there is a high risk to
life if there is a fire anywhere in the building |
|
Type L3 |
A
system protecting escape routes and adjacent rooms |
|
MANUAL
|
| |
|
Type M |
A
system that provides only for manual initiation of an alarm with the use of
manual call points |
|
Note |
Both P and L types of systems should also include the use of manual call
points, this is mandatory. |
System Design
Review
|
Type P1 |
For
a Type P1 where the protection of the property in the absence of people
working in or near parts of the building, that may be susceptible to fire
damage. Every part of the building should be suitably protected. For this
purpose each effectively enclosed space should be considered separately.
|
|
|
|
|
|
-
Voids not more than 800mm (8M) deep need not be protected unless fire or fire
products can spread through them from one part to another.
|
|
|
-
Shafts for elevators, lifts, hoists, escalators and enclosed chutes
through floors and stairways should be protected by detectors at the top
of the shaft and within 1.5m of openings on to each floor.
|
|
|
-
Where and escalator or staircase has a sloping ceiling a detector may need
to be sited on that ceiling.
|
|
|
-
Where rooms are divided by partitions or storage racks reaching to within
300mm of the ceiling each section should be protected separately.
|
|
|
-
Extra detectors may be needed to cope with structural features in a room.
|
|
|
-
Consideration must be given to possible adverse airflows when air
conditioning and ventilation systems are in use.
|
|
|
-
If a detector is concealed, it may be desirable to use a remote visible
indication of its operation.
|
|
|
-
Care should be taken when siting to ensure that adverse conditions such as
high levels of shock or vibration are not encountered.
|
|
Type P2 |
Areas covered by a Type P2 system, the siting of detectors should be similar
to that in a P1 system. If a fire started outside of the protected area, and
then spreads to the protected area, the ferocity of the fire would now be
much higher than if the fire started in the protected area. In order to
prevent such a spread of fire, areas protected by a type P2 system, should
be separated from unprotected areas by a fire resisting construction.
|
|
