FPASA BULLETIN SF 14
FIRE SAFETY FOR COMPUTER INSTALLATIONS
Electronic computer and data processing equipment are essential and commonplace tools
for business, industry, government and research groups. People quickly become
dependant on the equipment. A minor problem which causes a computer to “go down” can
temporarily immobilise an institution until the fault is rectified. This usually only taken a
few minutes. A serious fire, however, might disable an installation for days, resulting in
enormous losses.
Some computer fires
London, UK.
-Electrical fault ignited paper element in air conditioning duct.
Berkshire, UK.
-Short circuit in refrigeration unit of air conditioning system.
Newcastle, UK.
-Short circuit inside the computer cabinet. Detectors alerted the
brigade who were unable to extinguish the fire with extinguishers due
to its advanced state – a fixed gaseous system would have
extinguished the fire before their arrival.
Durban.
-Fire started in offices and spread to involve computer suite not
separated by fire resisting construction. Smoke detectors connected
to fire station activated but too late to save the suite. Computer tapes
in strong room survived the fire.
Port Elizabeth.
-Two months downtime. Heat and smoke from a small fire
immobilised a large computer centre.
Records
Fire protection considerations for software and data has to be made for computer suites
and also for servers, personal computers etc. found in offices.
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The records are stored on:
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hard magnetic discs
flexible magnetic discs
magnetic tapes
paper products (punch cards)
photographic material
electronic hardware
compact discs
Important and duplicate records should be stored in a separate room of at least two hour
fire resistance. Refer also to SABS 0141, Code of practice for the processing, testing and
storage of silver-gelatine microfilm for archival purposes.
Computer records are damaged by fire in a number of ways:
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A sustained ambient temperature of 80°C, can cause damage to functioning computer
equipment
temperature above 40°C will damage magnetic tapes and flexible discs but damages
incurred between 40°C and 50°C can generally be reconditioned
flexible discs deteriorate rapidly above 66°C
paper products may become damaged when the ambient temperature increases above
170°C
microfilm damage will occur at temperatures above 90°C in the presence of steam or at
260°C in dry heat
contamination with smoke and corrosive gases
Build to protect
Computers and electronic equipment are valuable and should be located in a detached
building or in an area segregated from other parts of the building. Segregation is achieved
by enclosing the room with at least one hour fire resistant walls and ceilings. When the
building has a medium fire load, eg: a factory, the minimum fire resistance should be two
hours with four hours fire resistance when the building has a high fire load, eg: a
warehouse.
Other rooms required to accommodate programmes, maintenance staff, paper supplies
and recorded data, should be separated from the computer room and combustible
materials kept to a minimum – metal furniture with fire retardant upholstery is
recommended. Minimum amounts of paper should be allowed in the computer room.
Construction details for computer rooms are outlined in BS 6266 and NFPA 75 and include
reference to:
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restriction of the combustibility of the floor space and ceiling
fire-stopping of openings into the room
correct electrical installation according to standards
air circulation through each cabinet (air filters used in the air conditioning system
should neither burn freely nor emit large volumes of smoke if attacked by flames)
separate electrical power supplies, distribution boards etc. housed in cut-off rooms
fire dampers which close automatically under emergency conditions fitted to air
conditioning ducting
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Fire detection is delayed when the air conditioning system transports smoke away
from smouldering computer equipment during the initial phase of the fire when
the smoke is highly diluted
Fire Protection
Statistics show that most fires involving computer hardware start in the computer cabinets.
A typical fire is of the smouldering variety caused by overheating of overloaded or faulty
electrical components. If the smouldering fire goes undetected, or if the electrical power is
not shut down, the heat of the electrical component can ignite combustible material in the
vicinity. The fire then spreads, fanned by the computer’s cooling equipment.
Fire protection should include:
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Portable fire-fighting equipment – carbon dioxide extinguishers should be provided near
the computer installation.
Hose-reels or water type extinguishers should be considered for protecting paper
storage areas. Hose-reels outside the computer room are advantageous in fighting
external fire which threatens the room.
Automatic fire detectors of a type which will detect a fire during its earliest stage.
Isonisation type detectors are most suitable for detecting clean burning fires – BS 6266
recommends an equal number of these and optical detectors in the computer room.
Other considerations regarding the selection and installation of smoke detectors –
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An unusually high density of detectors is appropriate to the concentration of valuable
machinery which is easily damaged by even small amounts of smoke.
They should be installed in any air spaces where fire may spread undetected eg:
ceilings and floors.
Avoid aerodynamically ‘dead’ zones created by the location of air conditioning ducts or
conformation of the room.
Detectors are usually arranged symmetrically but they should be at least 1,5 m from
fresh air flows.
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of
Under floor detectors should be: easily accessible, positioned to prevent dust from
initiating false alarms; and positioned with consideration to air flows.
Detectors in the air conditioning ducts will protect: the air conditioning plant rooms;
return-air system; and the supply air system.
Approximately 20 detectors per zone.
Acceptance testing is essential when the effects of the air conditioning and positioning
furniture upon the detectors are not predictable. SABS 0139 details the positioning of
the
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appropriate test fires used in these situations.
After installation by competent persons, a maintenance contract will ensure that regular
inspections are conducted.
Coincidence switching – two separate signals are received before activation of the
extinguishing system. This reduces the possibility of unwanted discharges.
Additional functions performed when detectors operate: sound alarms; stop fans;
close air conditioning dampers; isolate power supplies. A manual shut down
conducted in a predictable manner may be essential in some cases.
An annunciator board should be positioned outside the computer room.
Sprinkler Systems
The following considerations apply:
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Many computer suites throughout the world are protected by sprinklers.
Sprinklers will normally be selected if the rest of the building is sprinklered.
Provided adequate precautions are taken against accidental activation, sprinklers offer
a viable alternative to total flooding – especially where large volumes are concerned.
A typical system
A good concept utilises addressable smoke detectors inside computer cabinets. Having
detected smoke within a cabinet, pre-programmed de-energisation of the cabinet is
initiated. (See Fig. 1)
When an electrical component overheats (T1 > 100°C) and produces smoke, an
addressable smoke detector installed in the cabinet must respond to smoke density (DI) at
instant (a) Fig.2) – typical for a smouldering fire.
At instant (a), a control device initiates shut down of the power supply to the cabinet – a
pre-programmed measure, allowing the computer to operate without the particular cabinet
being energised.
Also at (a), an audio-visual pre-alarm is initiated in the room; available operators will then
be able to extinguish the fire.
If, however, the fire is not extinguished and the flames spread (T 2 > 400°C), ceiling
mounted detectors will respond to smoke density (D2) (Fig.2) and total flooding of the room
will be initiated.
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Fire Precautions
A high standard of housekeeping is essential to ensure the safety of computer installations.
Before staff leave premises after working hours they should check the following:
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all doors and hatches between rooms are closed
waste paper removed
ancillary equipment unplugged from sockets
master switches in OFF position
automatic fire extinguishing system on automatic control
all records returned to storerooms and safes
doors locked
Finally, concise evacuation and damage control plans should be compiled and regular
practices of evacuations conducted.
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Detection systems – design considerations
Floor area coverage per detector – BS 6626
Application
Recommended coverage per
detector
Remarks and
recommendations
Computer equipment room
(ceiling height about 3 m)
For minimum room protection,
a
detector for every 25 m².
Where
equipment,
or
information
justifies,
additional
expenditure,
detector coverage could be
reduced to 15 m²
Without ventilation: 20 m² - 30
m²
Where the earliest possible
warning
of fire in a cabinet is
required, there is no substitute
for the incorporation of a
detector or sensing point inside
the cabinet.
False floor, false ceilings
In false ceilings with beams the
lower figure should be taken. If
the beams are deep so as to
compartmentalise the space, a
detector should be fitted in
each such compartment.
With ventilation:
Tape stores
Electrical distribution boards
emergency power supplies
Peripheral
stores, etc.
Corridors
rooms:
offices,
(a) between 15 m² and 20 m² for
air velocities of 4 m/s or less
(b) 10 m² for air velocities greater
than 4 m/s
Room protection: 10 m² to 30 The greater the ventilation, the
m²
smaller fire coverage necessary
Room protection: 10 m² to 30 In installations with enclosed
m²
emergency power cabinets,
additional protection is ensured
by the installation of detectors
inside the cabinets.
Each room should have at least
one smoke detector
Not more than 12 m apart For corridors subdivided by
doors at least one detector in
each section.
Note: For coincidence systems, minimum recommended coverage areas should be used.
References:
Fire Protection for electronic data processing installations
British Standard Code of Practice BS 6266: 1982
Standard for the protection of Electronic Computer/Data processing equipment Code 75, NFPA
Fire Prevention No. 173, FPA UK
Information Bulletin, Siemens Ltd
Fire Protection Handbook, NFPA
Code of Practice for the Prevention, automatic detection and extinguishing of fire in buildings, SABS
0139
Published by
Fire Protection Association of Southern Africa
(Incorporated Association not for Gain)
(Reg.No. 73/00022/08)
P O Box 15467
Impala Park
1472
4/2000