Fire Enclosure Testing Method Statement
The following information is essential prior to Air Pressure
Testing attending site to carry out a Fire enclosure Integrity Test.
The procedures detailed below should be made available to all site
managers/engineers, project/contract managers to ensure the smooth
planning and completion of a fire enclosure Integrity Test.
Objective
The Integrity of an enclosure is defined as the ability of the
structure to adequately retain an extinguishing agent at a suitable
level and concentration to suppress a fire condition.
For any Gaseous Fire Suppression Installation to be effective,
the design concentration must first be achieved and then suitably
maintained within the risk - to achieve this, the test enclosure must
be effectively sealed to prevent excessive air leakage.
The Fire Integrity
Test has been developed to help locate the source of leaks and, from
the data collected, predict the retention time without the necessity
to actually discharge any extinguishant.
In order to determine with any degree of confidence that the
hazard area will hold the agent for the required time period, a Fire
Enclosure Integrity Test in accordance with ISO 14520 / NFPA must
be conducted.
The fire integrity test is usually based upon a descending interface
being formed; in this case the extinguishant is discharged into the
enclosure and gradually escapes through air leakage paths being replaced
by the ingress of air, thus forming a descending interface. The retention
period is the time it takes for this descending interface to reach
the tallest item of equipment requiring protection.
If this is less than the 10-minute requirement then the enclosure
will have been deemed to fail the fire integrity test and will require
remeadial sealing works.
1.
Test Methodology
Our Fan/s are temporarily located
within the test doorway to pressurise and depressurise the test enclosure. A series of pressure and airflow measurements
are taken from which the leakage characteristics of the enclosures
are established.
2.
Test Equipment
A enclosure Test Kit consists of a frame that will fit
into and seal a standard doorway in the enclosure, one or more variable
speed fans (if the enclosure is large) with low flow facilities, capable
of giving a differential pressure of not less that 25 Pa across the
enclosure boundary. To test larger enclosures we use our two/three
fan system to ensure we achieve the required pressure
3.
Enclosure Evaluation
Obtain or prepare a sketch plan showing walls, the location
of doors and other openings through which air will flow during the
test, along with the location of any ducts penetrating the enclosure
(including any dampers). Measure
the protected enclosure volume as necessary and record the following:
a. The gross volume of the protected enclosure,
Vg
b. The overall height of the test enclosure,
Ho
c. The height of the highest hazard within the
enclosure,
H
d. The Net Volume of the protected enclosure, V
e. The Quantity of extinguishant utilised in
the Discharge
Q
f. The Design Concentration,
C
Show the status (i.e. whether open or closed when the
system is discharged) of each door, hatch and damper, and which accesses
/ opening(s) is (are) to be used for the fan unit.
4. Fire
Integrity Test Procedure preparation (prior to the test)
All Dampers serving the test enclosure shall be closed
and the air conditioning / supply / extract fans switched off as if
in a discharge condition prior to the fire integrity test being conducted. If not, personnel should be readily available
to carry out these works just before the fire integrity test. If any specific arrangements have been incorporated
in the system design these should be compensated for within the test
programme (e.g. delayed operation of dampers, fan run down periods,
A/Cs not shutting down, etc).
All closable openings should be sealed and no temporary
sealing works should be in place unless previously agreed and arranged
by all parties. The temporary sealing or blanking off of fans, dampers,
ducts or any other openings etc is not permissible for insurance purposes;
if present these must and will be identified in the report, and as
a result will not probably not comply.
If any equipment has to be moved this must be carried
out by trained site personnel we are not permitted to move any items
of equipment without the permission of the client.
Procedure
a.
Advise supervisory personnel in the
area of the test.
b.
Remove objects likely to be disturbed
by the turbulence from the fan/s as this cause injury.
c.
Block open sufficient doors outside
the enclosure envelope to provide an adequate return path for air
between the fan unit and the enclosure leaks while correcting any
breach of any requirements of the facility, including requirements
for security, fire protection, environmental boundaries.
d.
Set all air-handling equipment and
extraction systems to the state they would be in at the time of a
system discharge.
e.
Close all doors and windows in the
enclosure envelope and affix warning notices.
f. The
enclosure will be pressurised to between 10 – 25 Pascals.
Client Requirements
In order to proceed with the
Fire Integrity Test the enclosure must be in a suitable condition
and have the following minimum requirements:
There must be a power supply available close (5 metres)
to the door of the enclosure in which the test is being conducted. This should be preferably 240 Vac (or 110 v)
- always confirm which supply is available. (please
note: if neither are available then the test cannot go ahead)
The door in which the fan kit is to be positioned should
have a clean frame and clear access to the front, rear and sides. This door will be open whilst the test is performed.
The door size should be between 30 to 44 inches wide and approx
100 inches tall. If the size differs from this always advise
prior to testing.
The test enclosure should be in a safe condition to work
in, e.g. free from asphyxiating hazards (well ventilated) and of a
reasonable temperature to work in.
It is recommended (but not essential) that no other services
or work are being undertaken at the actual time of the test, especially
if it interferes with the building envelope. It is also important
that no doors / windows are opened during the fire integrity test.
The extinguishing system (if installed) should be isolated
and in a safe mode of operation for the duration of the fire integrity
test (Manual Mode).
Time Scales for the Fire Integrity
test/s
Depending on the size of the area being tested, the pre-test
inspections, measurement and surveys will take approximately two hours
to complete on a room up to 1,000 m3. Larger test enclosures will usually take longer
to survey and this must be catered for.
The Test equipment (one fan unit) will take between 10
and 20 minutes to set up (as long as the access door is available)
once the equipment is at the location.
The fire integrity test will take between 10 minutes
to half an hour to complete depending upon the condition of the enclosure
and the leakage characteristics. If specific cooling considerations
need to be accounted for then the test duration can be shortened /
pulsed.
Results will be produced within the hour from the final
enclosure test performed with a detailed report following in the post
shortly afterwards.
Total expected time on site (excluding induction etc)
is; 4 hours for one enclosure or 6 hours for two enclosures (depending
upon size and number of engineers).
The
Size of the enclosure being tested
If an enclosure volume is between 1,500 m3
and 3,000 m3 then normally two fans will be required as
a minimum and the enclosure will take longer to test due to the additional
volume to survey, etc. This
will incur additional charges. If
an enclosure volume exceeds 5,000 m3 then more kits and
more engineers will be required at an additional cost and these would
need to be advised well in advance to ensure availability. It is essential
that time scales are agreed prior to attending site, our usual lead
in is approx 1 wk, however we can sometimes better this if we can
undertake the test out of hours, this can also reduce the impact of
on site testing during working hours.
Having set up and zeroed the equipment, the enclosure
under test is depressurised to approximately 15 Pascals. This is undertaken with the protected enclosure
set up to simulate that which would occur after a discharge, i.e.
HVAC shut down, dampers shut etc.
The door fan unit is then activated and run up to achieve a
room pressure approximating that, which would be created during an
Extinguishant discharge, e.g. the equivalent column pressure of the
extinguishant when discharged. The test room pressure required is calculated
from the initial concentration of extinguishant and the maximum height
of the protected test enclosure. If
it is not possible to achieve this pressure difference because the
test enclosure is excessively leaky, a pressure difference of at least
10 Pascals should be created before readings are taken.
All dampers are inspected to check that they are closing
properly. The walls, floor
and roof of the test enclosure are inspected for significant leaks,
and the cause of any major air currents noted / identified.
Finally, doors and hatches are inspected to ensure that they
are closing properly and that seals have been fitted.
Depending upon the
characteristics of the test enclosure and the nature and size of the
installed air handling plant, some parts of the leakage check may
be undertaken with the air conditioning still operating if temperature
build‑up in the enclosure is a particular problem.
The test enclosure room pressure and flow pressure measurement
(for each fan unit used) is measured and recorded. The gauges should remain stable for at least
30 seconds prior to the operator taking measurements. If the gauges do not remain steady the cause
should be investigated.
If the test enclosure fails to satisfy the requirements
a detailed survey is carried out (if permissible) making note of the
leakage areas to allow remedial sealing works to be carried out. This
can be undertaken there and then by pressurising the room and using
a smoke machine, this will show the exact air leakage paths, and enable
the contractor to directly seal the air leakage areas.
In general, most variations or fluctuations in the pressure
measurements will be caused by the wind. Damping equipment can be used to minimise the
effect of the wind upon the measurements, however, it is important
to effectively seal all external surfaces in an enclosure where pressure
variations caused by the wind have been noted.
Having achieved satisfactory readings of room pressure
and flow pressure, and performed an inspection of the enclosure under
test, the equipment is de‑activated and removed from the doorway(s)
in use. All signs and wedges must also be recovered.
If the measured leakage area yields predicted retention times
that are too short to be acceptable, a detailed inspection for leakage
sites may be undertaken while the protected envelope is depressurised,
remedial works carried out and the test enclosure re-tested.
It should be noted that there is no need to shut down
any Computer / Comms equipment within the test enclosure for the duration
of the fire integrity test, in general all machines can remain fully
operational. There is also no need to shut down re-circulating air
conditioning units, this is the cassette type mounted in the ceiling
void (or on the wall) or the large floor mounted units within the
test enclosure (sometimes located outside the risk area) if there
is a fresh air makeup then this is closed if a damper has been fitted.
The
only equipment which needs to be shut down is; a) the extraction system,
which is generally closed under normal operation and b) any dampers
fitted to fresh air supply ducts and return air extract ducts. This
is only for the duration of the fire integrity test, which, at most,
should only take ten minutes. Fusible link dampers, which are not
connected to the fire alarm system, are left in the normal operating
position.
Access is restricted if there is only one door to the
test enclosure (in which fan kit is located) and this is only for
a 10 minute duration. However,
if access is required, the test kit can be removed in 60 seconds.
If there are alternative doorways into the enclosure these can be
used to gain access and the test re-run when the door is closed.
Once all above works are finished, liase with the client and confirm that
all works have been completed to a satisfactory standard, that the
areas have been left clean and tidy and that the client is satisfied
with the manner in which the works have been completed and that the
standard is acceptable. The fire integrity test reports will be forwarded
within one working week thereafter
Guide
to achieving a positive Pressure Test - Sealing Works
The
NFPA 2001 standard for the fire protection industry specifically addresses
issues that impact on Enclosure Integrity Testing. Historically, the
vast majority of discharge test failures have been caused by lack
of enclosure integrity. The proper initial concentration is achieved,
but the enclosure doesn't retain it for the required time. The new NFPA Appendix B Enclosure Integrity
Test is a suitable alternative means of verifying adequate enclosure
integrity for total flooding systems. Similar rules have now been
adopted in the ISO 14520 & LPR 16:2000 universally recognising
enclosure leakage as a major cause for system failures.
The
Fire Enclosure Integrity Test on its own is not a complete replacement
for the discharge test. Other
aspects of the system installation must also be approved per section
4-7 in the body of the 1996 NFPA 2001 Clean Agent Standard.
1) Greater overall fire protection of the hazard will be obtained through
having at least a one-hour fire rated separation surrounding the enclosure.
Compartmentation is considered one of the key first elements
in effective fire protection.
2) Greater environmental control (humidity, dust and temperature) and lower
ongoing maintenance costs will be provided by a tight enclosure.
3) Greater protection from smoke contamination originating outside the hazard
is obtained with a tight enclosure.
4) The increased cost of providing additional drywall and dampers will be
offset by lower maintenance costs (possibly lower initial acceptance
test costs if a discharge test is not performed) and also reduced
costs to maintain an acceptably tight test enclosure over time.
5) Authorities Having Jurisdiction now require 12 Monthly Enclosure Integrity
Testing to ensure continued performance. Slab to slab walls make the enclosure easier
to "re-accept" in the future.
Careful Penetration Planning/coordination
Achieving
and maintaining a high degree of air tightness is facilitated by having
the location and design of certain penetrations, specifically for
cables, planned in advance. The
installation of round pipe sleeves or other engineered re-sealable
openings is recommended. Sufficient extra capacity should be installed
to handle expected future expansion.
Sealing openings between cables within bundles is a very common
and difficult problem to solve once all cables are in place.
Dampers (HVAC)
All
ducts leading into or out of the space must be mechanically dampered,
even if the air handler serving them will be shut down and the ducts
terminate at ceiling level. Dampers
should be smoke rated
Even
if a Clean Agent protected enclosure is designed and built to be as
tight as possible, a certain degree of leakage must be expected to
occur.
The
leakage mechanism is somewhat as follows:
During the
retention period, the agent/air mixture, being heavier than air, will
generally leak out of lower openings.
Air will enter through openings high in the room at the same
rate to replace it. If air-moving devices in the room are shut down,
this incoming air tends to collect at the top of the room. The upper level of the Clean Agent mixture descends
over time. This boundary layer
between the original agent/air mixture and the infiltrated air is
known as the descending interface.
However, if
any air moving equipment is left on during the retention period (blowers,
air conditioning units, and UPS equipment), the incoming air becomes
completely mixed with the original agent/air mixture.
This causes the average concentration throughout the room to
decay. This phenomenon is known as mechanical mixing.
If a descending
interface forms, the allowable height to which it can descend in l0
minutes is a crucial factor.
This minimum protected height is usually where the upper probe
would have been placed during a discharge acceptance test (tallest
equipment cabinets, usually consisting of essential equipment).
The
minimum protected height is best defined as: the highest combustible
item in the room and in certain cases the most essential item of equipment
is utilised as the required protected height.
Design the room and its equipment (cable trays are the most
common problem) so that all combustibles are kept below the 75% level
(measured from the floor slab). The 75% level is an NFPA 2001 guideline, and
allows for a reasonable amount of Clean Agent leakage (up to 25% of
the room volume) whilst not severely restricting the equipment design.
Small
rooms (say up to approximately 200 cubic metres) have historically
been the most difficult to pass using a discharge test. There appears
to be two reasons for this. One
is that Clean Agent is more likely to be lost during the initial discharge,
especially if there is an unprotected ceiling void above.
This appears to be reduced if a "soft" discharge
is used. Contact Clean Agent equipment manufacturers
for more guidance.
The
predominant reason appears to be because small rooms have much less
favourable surface to volume ratios.
For example, a 400 cubic metre room has ten times the volume
of a 40 cubic metre room, but has only three times the wall area.
Relatively speaking, the small room has to be much tighter
to retain the agent. As the
Room Integrity Test is even more stringent than the discharge test,
this can make small rooms difficult to accept if they aren't practically
airtight. In these circumstances it is extremely important that a
If
all air moving equipment is to be shut down in the event of a fire,
the Minimum Protected Height (e.g. 75% of room height) and Minimum
Initial Concentration should be specified in the bid request documents.
It is necessary to specify a minimum initial concentration to design
for if an Enclosure Integrity Test is to be used for acceptance.
It is recommended that the Minimum Protected Height be no higher
than 75% of the room height, especially if the enclosure volume is
less than 200 cubic metres.
Test Enclosure Integrity Specifications
On new installations,
it is generally the main contractor, if one is present, who is responsible
for the overall room tightness. The
Contractor in turn would then require that all his sub-contractors
perform the necessary sealing which relates to their work. Any work being done on the installation by second
level contractors (e.g. cable installers) not operating under the
Main Contractor must also be subjected to this requirement under their
contracts. If the Clean Agent
system is being installed as a retrofit, one contractor must be made
responsible for sealing existing holes.
If no building contractor is involved in the retrofit, the
Clean Agent installer may be able to arrange for this service.
The
prescriptive specifications give guidance on what must be sealed,
while the performance specification determines whether the job was
done right. In order to pass the Enclosure Integrity Test,
the contractor may have to seal items which are not specifically described
in the prescriptive specifications.
Enclosure Integrity Performance Specification
Enclosure leakage should be eliminated to at least
the degree necessary to enable the Clean Agent protected enclosure
to pass a test conducted in accordance with the 1996 NFPA 2001 Enclosure
Integrity Procedure. It is possible
to calculate in advance using NFPA 2001,Appendix
B, what the maximum allowable Equivalent Leakage Area would be for
the enclosure. If this is done the performance specification
could be even more specific.
Enclosure Integrity Prescriptive Specifications
The
following items cover enclosure leakage in a general fashion, and
should be placed in the General Contractor's specification. He should then repeat those appropriate to specific
subcontractors in their specifications. If the client or AHJ requires that the materials
and techniques used must produce a one or two-hour fire rated enclosure,
this must be specified.
Because
historically the walls and roof of unprotected ceiling voids above
suspended ceilings have not had to be well sealed to retain agent,
existing building practice, if retained, will produce enclosures where
large leakage areas will be measured, resulting in unacceptably low
predicted retention times. It is recommended that where possible the walls
and roofs of unprotected ceiling voids be sealed as tightly as the
protected enclosure below. If
this is not possible or practical (in a retrofit for example), it
is generally possible to accept the enclosure using the Suspended
Ceiling Leakage Neutralisation Method.
It is recommended however that every attempt be made to seal
the ceiling void first.
Test Enclosure Sealing Requirements
The perimeter walls of the protected test enclosure
should extend from the structural floor to the structural floor above,
or the roof / solid slab ceiling level.
Alternatively, the (suspended) ceiling of the test enclosure
should be of a solid plasterboard construction, taped and painted.
Access panels may be required if access is essential.
Where an under floor space continues out of the Clean
Agent protected area into adjoining rooms, airtight fire rated partitions
should be installed under the floor directly under above-floor border
partitions. These partitions should be caulked top and bottom.
If a removable floor tile extends under a doorway over such
a partition, it should either be: permanently sealed in place, installed
with a flexible seal between it and the wall below or the tile should
be discontinued at the doorway with a permanent airtight ledge created
up to which the floor tiles abut.
If adjoining rooms share the same under floor air handlers,
then the partitions should have dampers installed of the same type
as required for ductwork.
All holes, cracks, or penetrations
leading into or out of the protected area should be sealed. Pipe chases and cable trays should be sealed
around both the outside and inside at a point where they pass through
the envelope of the protected zone.
All walls should be caulked around the inside perimeter of
the room where the walls rest on the floor slab and where the walls
intersect the ceiling slab or roof above.
Porous block walls should be sealed slab-to-slab to
prevent gas from passing through the block.
Multiple coats of paint may be required.
All doors should have door sweeps or drop seals on
the bottoms, weather stripping around the jambs, latching mechanisms
and door closer hardware. In
addition, double doors should have a weather-stripped astral to prevent
leakage between doors and a co-ordinator to assure proper sequence
of closure.
Windows should have solid weather-stripping around
all joints. Glass to frame
and frame to wall joins should be sealed.
All floor drains should have traps designed to have
water or other compatible liquid in them at all times.
All unused and out-of-service ductwork leading into
or from a protected area should be permanently sealed off (airtight)
with metal plates caulked and screwed in place at the point where
they breach the envelope of the protected zone.
All ceiling tiles should have a weight of at least
5 pounds (2.27kg) per square foot.
Lightweight vinyl coated acoustic tiles should not be used.
The possibility of ceiling tiles being displaced during
a discharge should be addressed at the design stage. Possible options include tile clipping, nozzle
deflectors, lowering the nozzles a certain distance from the ceiling
and ensuring proper nozzle location.
Contact Clean Agent equipment manufacturers for guidance.
Clean Agent System Specifications
This section covers only the issue relating to the
Clean Agent system design, which has an impact on the Enclosure Integrity
Test. A complete specification
should cover the appropriate 1996 NFPA 2001 articles and features
of particular interest to the client.
The system should be designed and installed to provide
an adequate concentration throughout the protected enclosure upon
discharge, as calculated in NFPA 2001 or the relevant design documents.
The protected enclosure extends from the floor slab to (the slab above/the
suspended ceiling).
HVAC Specifications
Ductwork,in service with the building air handling
unit, should have gasketed low leak agent/smoke type dampers with
flexible seals (option: conforming to UL-555S "Standard for Leakage
Rated Dampers For Use in Smoke Control Systems", Class I leakage
rated). Rigid metal-to-metal blade seals should not
be used. Dampers should be
spring-loaded or motor-operated to provide near airtight shut-off. (Option: The dampers should be of the spring
close, motor open type.)
The
dampers should be installed as close as possible to the duct's point
of entry into the room. All duct joints between the damper and the duct
entry point should be sealed. The
gap between the damper frame and the duct wall should be sealed. A minimum 6" square access panel should
be installed to permit internal inspection of the damper.
It is recommended that whenever possible, any in-room
air conditioning units be shut down upon discharge to reduce the possibility
that they will expel the mixture from the sub-floor.
Ideally, the Clean Agent protected enclosure will be
a "dead" room from a static pressure standpoint by the time
the Clean Agent discharges. If
the dampers are truly tight, and the in-room air conditioning units
are shut down, close to zero pressure is usually achieved.
Occasionally, however, significant imbalances exist in the
building HVAC system, which could increase the leakage of Clean Agent
from the enclosure. If a significant
static pressure is uncovered during the Enclosure Integrity Test which
is not solved by improving damper seals or sealing leaks, it may prove
to be necessary to have that zone of the building's air handlers shut
down in addition to closing the dampers.
Approval/Acceptance Of
Clean Agent System
The following article covers only the acceptance of
the Clean Agent system, which is the Clean Agent installer's responsibility.
Historically, the vast majority of discharge test failures
have been caused by lack of enclosure integrity. Nonetheless, if a discharge test is not being
carried out, it is essential that other aspects of the system installation
be verified and tested.
The contractor should provide a test report. After the tests are completed and the system
has been accepted, the system should be brought to full operating
condition.
It is important to note that while the Clean Agent
contractor is often responsible for providing the Enclosure Integrity
Test, he is not responsible for the sealing unless specifically stated in his contract.
Guide to achieving a positive Pressure
Test - Sealing Works
The
NFPA 2001 standard for the fire protection industry specifically addresses
issues that impact on Enclosure Integrity Testing. Historically, the
vast majority of discharge test failures have been caused by lack
of enclosure integrity. The proper initial concentration is achieved,
but the enclosure doesn't retain it for the required time. The new NFPA Appendix B Enclosure Integrity
Test is a suitable alternative means of verifying adequate enclosure
integrity for total flooding systems. Similar rules have now been
adopted in the ISO 14520 & LPR 16:2000 universally recognising
enclosure leakage as a major cause for system failures.
The
Fire Enclosure Integrity Test on its own is not a complete replacement
for the discharge test. Other
aspects of the system installation must also be approved per section
4-7 in the body of the 1996 NFPA 2001 Clean Agent Standard.
1) Greater overall fire protection of the hazard will be obtained through
having at least a one-hour fire rated separation surrounding the enclosure.
Compartmentation is considered one of the key first elements
in effective fire protection.
2) Greater environmental control (humidity, dust and temperature) and lower
ongoing maintenance costs will be provided by a tight enclosure.
3) Greater protection from smoke contamination originating outside the hazard
is obtained with a tight enclosure.
4) The increased cost of providing additional drywall and dampers will be
offset by lower maintenance costs (possibly lower initial acceptance
test costs if a discharge test is not performed) and also reduced
costs to maintain an acceptably tight enclosure over time.
5) Authorities Having Jurisdiction now require 12 Monthly Enclosure Integrity
Testing to ensure continued performance. Slab to slab walls make the enclosure easier
to "re-accept" in the future.
Penetration Planning
Achieving
and maintaining a high degree of air tightness is facilitated by having
the location and design of certain penetrations, specifically for
cables, planned in advance. The
installation of round pipe sleeves or other engineered re-sealable
openings is recommended. Sufficient extra capacity should be installed
to handle expected future expansion.
Sealing openings between cables within bundles is a very common
and difficult problem to solve once all cables are in place.
Dampers (HVAC)
All
ducts leading into or out of the space must be mechanically dampered,
even if the air handler serving them will be shut down and the ducts
terminate at ceiling level. Dampers
should be smoke rated
Even
if a Clean Agent protected enclosure is designed and built to be as
tight as possible, a certain degree of leakage must be expected to
occur.
The
leakage mechanism is somewhat as follows:
During
the retention period, the agent/air mixture, being heavier than air,
will generally leak out of lower openings.
Air will enter through openings high in the room at the same
rate to replace it. If air-moving
devices in the room are shut down, this incoming air tends to collect
at the top of the room. The
upper level of the Clean Agent mixture descends over time.
This boundary layer between the original agent/air mixture
and the infiltrated air is known as the descending interface.
However,
if any air moving equipment is left on during the retention period
(blowers, air conditioning units, and UPS equipment), the incoming
air becomes completely mixed with the original agent/air mixture.
This causes the average concentration throughout the room to
decay. This phenomenon is known as mechanical mixing.
If
a descending interface forms, the allowable height to which it can
descend in l0 minutes is a crucial factor.
This minimum protected height is usually where the upper probe
would have been placed during a discharge acceptance test (tallest
equipment cabinets, usually consisting of essential equipment).
The
minimum protected height is best defined as: the highest combustible
item in the room and in certain cases the most essential item of equipment
is utilised as the required protected height.
Design the room and its equipment (cable trays are the most
common problem) so that all combustibles are kept below the 75% level
(measured from the floor slab). The
75% level is an NFPA 2001 guideline, and allows for a reasonable amount
of Clean Agent leakage (up to 25% of the room volume) whilst not severely
restricting the equipment design.
Small
rooms (say up to approximately 200 cubic metres) have historically
been the most difficult to pass using a discharge test. There appears
to be two reasons for this. One
is that Clean Agent is more likely to be lost during the initial discharge,
especially if there is an unprotected ceiling void above.
This appears to be reduced if a "soft" discharge
is used. Contact Clean Agent equipment manufacturers
for more guidance.
The
predominant reason appears to be because small rooms have much less
favourable surface to volume ratios.
For example, a 400 cubic metre room has ten times the volume
of a 40 cubic metre room, but has only three times the wall area.
Relatively speaking, the small room has to be much tighter
to retain the agent. As the Room Integrity Test is even more stringent
than the discharge test, this can make small rooms difficult to accept
if they aren't practically airtight. In these circumstances it is
extremely important that a
If
all air moving equipment is to be shut down in the event of a fire,
the Minimum Protected Height (e.g. 75% of room height) and Minimum
Initial Concentration should be specified in the bid request documents.
It is necessary to specify a minimum initial concentration to design
for if an Enclosure Integrity Test is to be used for acceptance.
It is recommended that the Minimum Protected Height be no higher
than 75% of the room height, especially if the enclosure volume is
less than 200 cubic metres.
Test Enclosure Integrity Specifications
On
new installations, it is generally the main contractor, if one is
present, who is responsible for the overall room tightness.
The Contractor in turn would then require that all his sub-contractors
perform the necessary sealing which relates to their work. Any work being done on the installation by second
level contractors (e.g. cable installers) not operating under the
Main Contractor must also be subjected to this requirement under their
contracts. If the Clean Agent system is being installed
as a retrofit, one contractor must be made responsible for sealing
existing holes. If no building
contractor is involved in the retrofit, the Clean Agent installer
may be able to arrange for this service.
The
prescriptive specifications give guidance on what must be sealed,
while the performance specification determines whether the job was
done right. In order to pass the Enclosure Integrity Test,
the contractor may have to seal items which are not specifically described
in the prescriptive specifications.
Enclosure Integrity Performance Specification
Enclosure leakage should be eliminated to at least
the degree necessary to enable the Clean Agent protected enclosure
to pass a test conducted in accordance with the 1996 NFPA 2001 Enclosure
Integrity Procedure. It is possible
to calculate in advance using NFPA 2001,Appendix
B, what the maximum allowable Equivalent Leakage Area would be for
the enclosure. If this is done the performance specification
could be even more specific.
Enclosure Integrity Prescriptive Specifications
The
following items cover enclosure leakage in a general fashion, and
should be placed in the General Contractor's specification. He should then repeat those appropriate to specific
subcontractors in their specifications. If the client or AHJ requires that the materials
and techniques used must produce a one or two-hour fire rated enclosure,
this must be specified.
Because
historically the walls and roof of unprotected ceiling voids above
suspended ceilings have not had to be well sealed to retain agent,
existing building practice, if retained, will produce enclosures where
large leakage areas will be measured, resulting in unacceptably low
predicted retention times. It is recommended that where possible the walls
and roofs of unprotected ceiling voids be sealed as tightly as the
protected enclosure below. If
this is not possible or practical (in a retrofit for example), it
is generally possible to accept the enclosure using the Suspended
Ceiling Leakage Neutralisation Method.
It is recommended however that every attempt be made to seal
the ceiling void first.
Test Enclosure Sealing Requirements
The perimeter walls of the protected test enclosure
should extend from the structural floor to the structural floor above,
or the roof / solid slab ceiling level.
Alternatively, the (suspended) ceiling of the test enclosure
should be of a solid plasterboard construction, taped and painted.
Access panels may be required if access is essential.
Where an under floor space continues out of the Clean
Agent protected area into adjoining rooms, airtight fire rated partitions
should be installed under the floor directly under above-floor border
partitions. These partitions
should be caulked top and bottom.
If a removable floor tile extends under a doorway over such
a partition, it should either be: permanently sealed in place, installed
with a flexible seal between it and the wall below or the tile should
be discontinued at the doorway with a permanent airtight ledge created
up to which the floor tiles abut. If adjoining rooms share the same under floor
air handlers, then the partitions should have dampers installed of
the same type as required for ductwork.
All holes, cracks, or penetrations
leading into or out of the protected area should be sealed. Pipe chases and cable trays should be sealed
around both the outside and inside at a point where they pass through
the envelope of the protected zone.
All walls should be caulked around the inside perimeter of
the room where the walls rest on the floor slab and where the walls
intersect the ceiling slab or roof above.
Porous block walls should be sealed slab-to-slab to
prevent gas from passing through the block.
Multiple coats of paint may be required.
All doors should have door sweeps or drop seals on
the bottoms, weather stripping around the jambs, latching mechanisms
and door closer hardware. In
addition, double doors should have a weather-stripped astral to prevent
leakage between doors and a co-ordinator to assure proper sequence
of closure.
Windows should have solid weather-stripping around
all joints. Glass to frame
and frame to wall joins should be sealed.
All floor drains should have traps designed to have
water or other compatible liquid in them at all times.
All unused and out-of-service ductwork leading into
or from a protected area should be permanently sealed off (airtight)
with metal plates caulked and
screwed in place at the point where they breach the envelope of the
protected zone.
All ceiling tiles should have a weight of at least
5 pounds per square foot. Lightweight
vinyl coated acoustic tiles should not be used.
The possibility of ceiling tiles being displaced during
a discharge should be addressed at the design stage. Possible options include tile clipping, nozzle
deflectors, lowering the nozzles a certain distance from the ceiling
and ensuring proper nozzle location.
Contact Clean Agent equipment manufacturers for guidance.
Clean Agent System Specifications
This section covers only the issue relating to the
Clean Agent system design, which has an impact on the Enclosure Integrity
Test. A complete specification
should cover the appropriate 1996 NFPA 2001 articles and features
of particular interest to the client.
The system should be designed and installed to provide
an adequate concentration throughout the protected enclosure upon
discharge, as calculated in NFPA 2001 or the relevant design documents.
The protected enclosure extends from the floor slab to (the slab above/the
suspended ceiling).
HVAC Specifications
Ductwork,in service with the building air handling
unit, should have gasketed low leak agent/smoke type dampers with
flexible seals (option: conforming to UL-555S "Standard for Leakage
Rated Dampers For Use in Smoke Control Systems", Class I leakage
rated). Rigid metal-to-metal blade seals should not
be used. Dampers should be
spring-loaded or motor-operated to provide near airtight shut-off. (Option: The dampers should be of the spring
close, motor open type.)
The
dampers should be installed as close as possible to the duct's point
of entry into the room. All duct joints between the damper and the duct
entry point should be sealed. The
gap between the damper frame and the duct wall should be sealed. A minimum 6" square access panel should
be installed to permit internal inspection of the damper.
It is recommended that whenever possible, any in-room
air conditioning units be shut down upon discharge to reduce the possibility
that they will expel the mixture from the sub-floor.
Ideally, the Clean Agent protected enclosure will be
a "dead" room from a static pressure standpoint by the time
the Clean Agent discharges. If
the dampers are truly tight, and the in-room air conditioning units
are shut down, close to zero pressure is usually achieved.
Occasionally, however, significant imbalances exist in the
building HVAC system, which could increase the leakage of Clean Agent
from the enclosure. If a significant
static pressure is uncovered during the Enclosure Integrity Test which
is not solved by improving damper seals or sealing leaks, it may prove
to be necessary to have that zone of the building's air handlers shut
down in addition to closing the dampers.
Approval/Acceptance Of
Clean Agent System
The following article covers only the acceptance of
the Clean Agent system, which is the Clean Agent installer's responsibility.
Historically, the vast majority of discharge test failures
have been caused by lack of enclosure integrity. Nonetheless, if a discharge test is not being
carried out, it is essential that other aspects of the system installation
be verified and tested.
The contractor should provide a test report. After the tests are completed and the system
has been accepted, the system should be brought to full operating
condition.
It is important to note that while the Clean Agent
contractor is often responsible for providing the Enclosure Integrity
Test, he is not responsible for the sealing unless specifically stated in his contract.
The following information is essential prior to Air Pressure
Testing attending site to carry out a Fire enclosure Integrity Test.
The procedures detailed below should be made available to all site
managers/engineers, project/contract managers to ensure the smooth
planning and completion of a fire enclosure Integrity Test.
Objective
The Integrity of an enclosure is defined as the ability of the
structure to adequately retain an extinguishing agent at a suitable
level and concentration to suppress a fire condition.
For any Gaseous Fire Suppression Installation to be effective,
the design concentration must first be achieved and then suitably
maintained within the risk - to achieve this, the test enclosure must
be effectively sealed to prevent excessive air leakage.
The Fire
Integrity Test has been developed to help locate the source of leaks
and, from the data collected, predict the retention time without the
necessity to actually discharge any extinguishant.
In order to determine with any degree of confidence that the
hazard area will hold the agent for the required time period, a Fire
Enclosure Integrity Test in accordance with ISO 14520 / NFPA must
be conducted.
The fire integrity test is usually based upon a descending interface
being formed; in this case the extinguishant is discharged into the
enclosure and gradually escapes through air leakage paths being replaced
by the ingress of air, thus forming a descending interface. The retention
period is the time it takes for this descending interface to reach
the tallest item of equipment requiring protection.
If this is less than the 10-minute requirement then the enclosure
will have been deemed to fail the fire integrity test and will require
remeadial sealing works.
4.
Test Methodology
Our Fan/s are temporarily located
within the test doorway to pressurise and depressurise the test enclosure.
A series of pressure and airflow measurements are taken from
which the leakage characteristics of the enclosures are established.
5.
Test Equipment
A enclosure Test Kit consists of a frame that will fit
into and seal a standard doorway in the enclosure, one or more variable
speed fans (if the enclosure is large) with low flow facilities, capable
of giving a differential pressure of not less that 25 Pa across the
enclosure boundary. To test larger enclosures we use our two/three
fan system to ensure we achieve the required pressure
6.
Enclosure Evaluation
Obtain or prepare a sketch plan showing walls, the location
of doors and other openings through which air will flow during the
test, along with the location of any ducts penetrating the enclosure
(including any dampers). Measure
the protected enclosure volume as necessary and record the following:
a. The gross volume of the protected enclosure,
Vg
b. The overall height of the test enclosure,
Ho
c. The height of the highest hazard within the
enclosure,
H
d. The Net Volume of the protected enclosure, V
e. The Quantity of extinguishant utilised in
the Discharge
Q
f. The Design Concentration,
C
Show the status (i.e. whether open or closed when the
system is discharged) of each door, hatch and damper, and which accesses
/ opening(s) is (are) to be used for the fan unit.
4. Fire
Integrity Test Procedure preparation (prior to the test)
All Dampers serving
the test enclosure shall be closed and the air conditioning / supply
/ extract fans switched off as if in a discharge condition prior to
the fire integrity test being conducted. If not, personnel should be readily available
to carry out these works just before the fire integrity test. If any specific arrangements have been incorporated
in the system design these should be compensated for within the test
programme (e.g. delayed operation of dampers, fan run down periods,
A/Cs not shutting down, etc).
All closable openings should be sealed and no temporary
sealing works should be in place unless previously agreed and arranged
by all parties. The temporary sealing or blanking off of fans, dampers,
ducts or any other openings etc is not permissible for insurance purposes;
if present these must and will be identified in the report, and as
a result will not probably not comply.
If any equipment has to be moved this must be carried
out by trained site personnel we are not permitted to move any items
of equipment without the permission of the client.
Procedure
f.
Advise supervisory personnel in the
area of the test.
g.
Remove objects likely to be disturbed
by the turbulence from the fan/s as this cause injury.
h.
Block open sufficient doors outside
the enclosure envelope to provide an adequate return path for air
between the fan unit and the enclosure leaks while correcting any
breach of any requirements of the facility, including requirements
for security, fire protection, environmental boundaries.
i.
Set all air-handling equipment and
extraction systems to the state they would be in at the time of a
system discharge.
j.
