Note: Descriptions are shown in the official language in which they were submitted.
CA 02194200 2000-OS-17
METHOD OF VENTING SMOKE
FROM HIGHRISE RESIDENTIAL BUILDINGS
Technical Field
The invention relates to methods for removing smoke
from highrise residential buildings in the event of a fire.
More particularly the invention relates to a method for
removing smoke from highrise residential-buildings by supply
ing or exhausting air through a common duct connected to the
building corridors.
Background
Building codes generally require that highrise
buildings have a system capable of removing smoke caused by a
fire. Removal of smoke from corridors is important both as
part of the firefighting smoke purging operations generally
and to assist firefighters by improving visibility so that the
location of the fire can be determined and the fire extin
guished.
In highrise residential buildings, venting to remove
smoke is largely achieved through openable windows. Within
internal corridors, where there are no external openable
windows, venting of smoke can be effected through the building
air handling system. In prior art systems, separate supply
and exhaust shafts are provided and connected to each floor's
corridor through motor-controlled damper. A disadvantage of
the prior art system is that it thus requires two motorised
dampers per floor and an expensive control system and wiring.
To maintain reliability of the system, extensive maintenance
and testing is required. There is therefore a need for a
simpler, less expensive but effective system for venting smoke
from the corridors of highrise buildings.
Brief Description of Drawings
In drawings which illustrate a preferred embodiment
of the invention:
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Fig. 1 is a schematic diagram showing the system of the
invention in normal mode;
Fig. 2 is a schematic diagram showing the system of the
invention in pressurization mode;
Fig. 3 is a schematic diagram showing the system of the
invention in exhaust mode;
Fig. 4 is a schematic diagram showing the system of the
invention where smoke is in the ventilation shaft;
Fig. 5 is a schematic diagram showing the system of the
invention where smoke is in the corridor;
Fig. 6 is a schematic diagram showing a typical corridor
layout;
Fig. 7 is a schematic diagram showing a typical central
core floor plan;
Fig. 8 is a schematic diagram showing a prior art system
in supply mode; and
Fig. 9 is a schematic diagram showing a prior art system
in exhaust mode.
Summary of Invention
The invention provides a method of venting smoke
from a building having a plurality of floors, each floor
having a plurality of suites with openable windows, each suite
opening into a corridor, comprising the steps of:
a) providing a venting shaft communicating with
each floor;
b) providing an air supply and exhaust grille
opening into each corridor and communicating with
the venting shaft;
c) providing a supply source of pressurized air,
and an exhaust source of reduced pressure each
communicating with the venting shaft, and damper
means for selectively closing or opening the com-
munication of the supply source of pressurized air
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and exhaust source of reduced pressure to the
venting shaft;
d) under conditions where pressure is desired in
at least one of the corridors, activating the
supply source, opening the communication of the
supply source to the venting shaft and closing the
exhaust source communication to the venting shaft;
and
e) under conditions where venting of smoke or air
is desired in at least one of the corridors, acti
vating the exhaust source, opening the communica
tion of the exhaust source to the venting shaft and
closing the supply source communication to the
venting shaft.
Description
Figures 8 and 9 show the prior art design for a
corridor smoke venting system in a residential building. The
corridor area of each floor 10, 12, 14 is equipped with a
supply air grille 16 connected by vents 18 to supply air fan
20. (The grilles typically are provided with a balancing
damper as shown). A motorized damper 22 controls the flow of
air from the supply air fan to the supply air grille. The
corridor area of each floor is also equipped with an exhaust
air grille 16 connected by vents 18 to smoke exhaust fan 28.
A motorized damper 24 controls the flow of air from the
exhaust grille 24 to the smoke exhaust fan 26.
In the normal supply mode of the prior art system
shown in Fig. 8, supply dampers 22 are open and exhaust
dampers 24 are closed. Thus the supplying air will also serve
to pressurize the corridor with respect to the adjoining rooms
or suites, and the normal flow of air is from the supply air
grille 16 through the corridor into the rooms and out of the
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exterior windows 30 or kitchen exhaust systems within the
suites (not shown).
In the event a fire alarm is triggered, as shown in
Fig. 9, the supply air fan 20 shuts down, all supply dampers
22 close and the exhaust air damper 24 on the floor where the
fire is located will open to clear the corridors of smoke.
The opening of the exhaust air damper 24 may be either manual
or automatic. Operation is normally controlled by the fire
alarm panel, sometimes called the Central Alarm and Control
Facility (CALF). Air is then pulled out along the corridor by
the exhaust system, which may cause some smoke to enter the
corridor system if a fire is within a suite. This is problem-
atic as it may hinder firefighters and cause additional smoke
damage.
Another disadvantage of the prior art system is that
it requires two motorised dampers 22, 24 per floor and an
expensive control system and wiring. To maintain reliability
of the system, extensive maintenance and testing is required.
The present invention is a "push/pull" venting
system which provides a simpler and therefore more reliable
venting system. It uses one ventilation shaft 44 for both
supply and exhaust through ducts 41. A single air grille 42
with a balancing damper is provided on each floor. The supply
air fan 20 and exhaust fan 28 are connected to the common
ventilation shaft 44. As in the prior art system, the supply
air fan remains operational under normal conditions, as shown
in Fig. 1, with supply damper 43 open and exhaust damper 45
closed. The supplying air pressurizes the corridor and helps
keep odours originating in one suite from migrating to the
core area and other suites.
In the event of a fire in a suite, as shown in Fig.
2, the supply air continues to operate to push air into the
corridor in the same way as under normal conditions. In most
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cases this will assist in confining the smoke to the suites to
minimize damage to non-fire suites and corridors. This also
assists in forcing smoke out through the exterior openings and
leaks in the building exterior.
In the event of a fire in a corridor, as shown in
Fig. 3, a corridor smoke detector 47 will detect the fire and
sound an alarm. On activation of a corridor smoke detector,
the corridor supply fan 20 will stop and the supply damper 43
closes. The exhaust damper 45 opens and the exhaust fan 28
then starts to operate to exhaust air from all floors and
smoke from the corridor where the fire is located, through the
same ducting 41, 44 used for supply.
The system has fire dampers 50 at each floor which
remain open to exhaust all floors simultaneously, except when
a high local air/gas temperature causes ther damper to close
to prevent f ire f rom spreading through the vents . The exhaust
fan is sized to vent the total flow from all floors. The flow
through the exhaust grilles 42 is balanced to prevent smoke
from entering non-fire floors and to provide minimum flow
rates for smoke exhaust. Manual controls are provided in the
fire alarm panel so that firefighters may control whether to
vent or pressurize the corridors depending on whether smoke in
the corridor is originating in the ventilation shaft 40 (see
Fig. 4) or in a suite (see Fig. 5).
The invention thus provides a system which elimin-
ates the individually motorized damper controls at each floor
level. The exhaust system can be actuated manually at the
Central Alarm and Control Facility or automatically by the
corridor smoke detector.
To provide an operable system according to the
invention, a minimum exhaust rate must be achieved at each
floor level to vent the corridors of smoke. It has been found
that six air changes per hour for the corridor plus three
changes per hour for the largest suite are acceptable
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guidelines. The supply rate is determined according to
standard engineering practice to provide smoke control and
normal ventilation/pressurization requirements. To achieve
both pressurization and smoke venting tasks, the supply/
exhaust grilles at each floor level must be carefully selected
and balanced. Grille characteristics, duct sizing, supply and
exhaust fan characteristics, ambient temperatures and
anticipated smoke temperatures must all be taken into account .
The forces required to open exit doors with or
without the operation of the venting system must be taken into
account to ensure they are nor excessive. Also the combined
presence and effects of elevator and stair shafts, building
leakages, smoke control systems, window breakages and door
openings must be analyzed to ensure that the smoke venting
system does not adversely affect the movement of smoke in the
building.
For proper operation, emergency power must be
provided to the fans and controls to ensure operation for a
period of at least one hour in the event of a power failure.
Also conductors providing power to the supply and exhaust fans
must be passively protected from a fire in the floors being
pressurized/vented, to survive a one hour standard fire.
Testing
Field testing of the system is necessary to ensure
that the designed exhaust capacity is achieved on all floors
and to confirm that the venting system does not result in
adverse smoke movement. The construction of the building and
most of its facilities must be substantially completed before
the field testing can be meaningfully conducted. This
includes the building envelope and all external windows,
internal partitions including the corridors, doors, floorings
including carpeting, other smoke control systems, balancing of
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corridor air supply and smoke exhaust system, and preferably
fire alarm system and corresponding interlocks and controls.
The field tests are conducted in four groupings:
a) Functional tests
All the functional controls for fire alarms and inter-
locks, remote fan damper operations, automatic supply/ exhaust
mode changeover, elevator controls are tested and verified.
b) Base Measurements
Pressure differentials across selected barriers within
the corridor smoke venting system are measured. The measured
values provide the reference data for the venting system.
c) Pressure and Flow Measurements
Pressure differentials across the same barriers as the
base measurements are measured with the corridor smoke venting
system running and repeated with various combinations of door
and window openings. Other forms of smoke control systems, if
designed to run with the corridor venting system are operated
simultaneously during the measurements. The exhaust flow
rates at selected points are verified.
d) Smoke Bomb tests
Smoke bombs or smoke generators are actuated at selected
locations to provide a visual indication of the corridor
venting system.
As will be apparent to those skilled in the art in
the light of the foregoing disclosure, many alterations and
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modifications are possible in the practice of this invention
without departing from the spirit or scope thereof. Accord-
ingly, the scope of the invention is to be construed in accor-
dance with the substance defined by the following claims.
