CA1224959A - System for inhibiting the spread of fire in a building structure - Google Patents

Abstract

A SYSTEM FOR INHIBITING THE
SPREAD OF FIRE IN A BUILDING STRUCTURE
ABSTRACT

Closure means are provided in the delivery and/or vent paths of an air conditioning system together with control means which respond to the presence of combustion in the associated compartment of a building structure to effect closure of the closure means when combustion therein is detected. Preferably closure means are provided at the entry and exit points of both the vent and delivery lines to each compartment so that the compartment in which combustion starts is automatically sealed off from the other compart-ments to inhibit the spread of the combustion products through the air conditioning system. It is also preferred that the closure means, when moved to the closed position, divert the combustion products into a vent passage or service duct leading directly to the outside of the building structure.

Description

r~

~YSTEM FOR INHIBITING THE SPREAD
-0~ E IN A BUILDING STRUC~URE

,I?~ELD AND BACKGROUND OF THE INVENTION

This invention relates to systems for inhibiting the spread of fire in a building structure.
An air conditioning system in a building structure requires a delivery path for delivering conditioned air to each compartment of the building and a ~ent path for extract-ing foul air from each compartment to maintain pressure balances and habitable conditions in those compartments.
The building services, e.g. ducting, which provide these delivery and vent paths must pass through walls of the compartments. Therefore even if the compar-tment walls are constructed to provide a measure of fire retardation the products of a fire in one compartment can spread to other compartments through the air conditioning system. Commonly

2~ when the fire starts in carpetting, curtaining and furnit~ure padding, a large quantity of smoke and toxic gases is produced.before the combustion spreads through flames and intense heat. It is often the inhalation of the smoke and toxic fumes th~t is the greatest danger to life before there is any substantial spread of flames.

SUMMARY OF THE INVENTION

According to the invention, there is provided a system for inhibiting the spread of the products of combustion within a building structure, comprising closuxe means for mounting in the air conditioning delivery and/or vent paths associated with a compartment of a bui~ding structure, and control means responsive to the presence of combustion, preferably a smoke de-tector, which control means when actuated effect closure of said closure means~ The closure - means should act to close at least the vent path at or adjacent the point where it exits from the compartment. I

~ 2 It is advantageous to pro~ide also said closure means in the air delivery path at or ad~acent lts point of entry into the compartment, Such closure means would also be closed automatically when said control means are actuated in order to prevent further air from being pumped into the compartment thereby to assist in causing sti~ling of the fire in the compartment.
Preferably closure means are provided in said vent path, and most preferably also in said delivery path at or adjacent at their points of entry to and exit from said compartment. When closure means are so provided in both the delivery and vent paths both at entry to and exit from the compartment, it is possible to seal off quickly the entire compartment once combustion is detected. Therefore when for example a smoke detector or any one of a plurality of such detectors in the compartment detects smoke and other products of combustion, a control system is actuated t~
trigger closure of said closure means in the delivery and vent ducts where they enter and exit the compartment. In 2~ this way a fire can be contained and confined within the compartment. Since pressurized air is no longer pumped into the compartment, the air pressure balance therein is main-tained substantially constant and the fire is thereby denied an air supply so that the increasing concentration of smoke and other products of combustion tends to douse the fire.
In a building structure, each compartment would generally be provided with a set of the aforesaid closure means and a control system therefor which includes detectors for location in the respective compartments so that a fire starting in any individual compartment can be confined to that compartment.
The aforesaid control means may include means to give an alarm and/or advise a control panel of the actuation of the presence of combustion.
The invention further provides a method of inhibiting the spread of the products of combustion within a building structure, which method comprises detecting the presence of combustion in a compartment of the building structure and in response thereto automatically closing an air conditioning J~ ~?~i'3~

.. ~ 3 ~

~en~ path fox ex~rac~;ing foul air fxom the çompartment, at or adjacent the point where the vent path exits from the compartment, ~dvantageously the air conditioning delivery path is also closed automatically at or adjacent its point o~ entry into the compartment~ Most preferably the vent path, and desirably also the delivery path, is closed automatically at or adjacent its points of entry to, and e~it from, the compartment.
It is particularly advantageous to use in a system ~0 according to the invention, at least one duct closure assembly comprising a duct or duct section comprising closure means movably mounted in the duct or duct section between an open position in which it permits fluid flow through the duct and a closed position in which it inhibits such fluid flow, ~5 and vent means in the wall of the duct or duct section, the arrangement being such that, in said open position, the closure means inhibits flow through said vent means an~, in said closed position, the closure means inhibits flow through the duct or duct section while allowing substantially 2Q unrestxicted flow through said vent means. The closure means may be controlled by control means which are responsive ~ to the presence of combustion, e.g. smoke and/or heat detec-tion means. For example the closure means can be used in conjunction with one or more smoke detectors which when activated produce a signal to release a latching device holding the closure means in its open position, whereupon the closure means moves under gravity or under the action of biassing means, e.g. a spring, to its closed position.
Apart from use of the aforesaid duct or duct section assembly in the above described system where the products of combustion are confined within the compartment in which the combustion originates, such an assembly can be used in an arrangement whereby the vent aperture communicates with a flue duct e~tending outside the building structure thereby to discharge the products of combustion to the ambient atmosphere. The building structure could be provided with a ser~es of such flue ducts for discharging combustion products to atmosphere at each floor level. Another possibility is to use lift or other purpose made shafts for such discharge flue r~ r~

ducts.
Yet a~other possibillty could ~e to retuxn the results of eo~bustion baek into the purpose made ~ising Builders Ser~iees Duct from which both de~ivery and extract ducts could e~anate.
An extraction fan or fans could be provided to draw combustion products through the lift or similar shaft. The fan(s) could be started automatically by the aforesaid control means which, when actuated, causes closing of said closure 1~ means.
An embodiment of the invention provides an assembly comprising a duct extending through a partition between separate compartments of a building structure for passage of air therebetween, closure means movably mounted in the ~5 duct between an open position in which it permits air flow through the duct and a closed position in which it inhibits such air flow, control means to maintain the closure means in its open position which control means are responsive to the presence of combustion to release the closure means when com~ustion is detected and the closure means being adapted to move to its closed position when so released, and a vent - aperture in the duct, the arrangement being sueh that, in its open position,-the elosure means inhibits flow through said ~ent aperture and, in its elosed position, the closure means inhibits flow through the duct while allowing substan-tially unrestricted flow through the vent aperture.
In some embodiments of the invention, said ~ent aperture, which is generally in an upper part of the wall of the duet, may eommunieate with a vent passage leading to the outside of the building structure. Preferably the vent passage communicates with a plurality of compartments of the build-ing structure.
The closure means may be in the form of a pivotally mounted elosure member, e.g a hinged flap, The invention ineludes a duet or duet seetion for an assembly as aforesaid, whieh d~et has therein said elosure means mounted as afore-said, said means to maintain the closure member in its open position and said ~ent aperture which is controlled by the closure means as aforesaid.

~ 5 -The inve~ti~n further provides ~ method of controlling an air ~low in a duct extending through a partition between separate co~par~ments of a building structure, which c~mprises provi~ng in the' duct closure rneans held in an open position permitting air flow through the duct and closing a vent aperture in the wall of the duct by means responsive to the presence of combustion which are actuated, when a particular temperature is exceeded, to release the closure means to close the duct to prevent hot air and fumes ~0 and other material created by a fire in one compartment ~rom reaching another compartment and t~ divert the hot air and fumes through said vent aperture for return to said one compartment or for venting to the outside of the building structure.
~5 An advantage of such an assembly is that it provides a means of diverting the pressurized air carrying the products of a conflagration either back into the compartment in which the fire started or directly to the outside of the building structure. When the air is returned to the compar~ment of the fire there will be a tendency to douse the fire as the increasing concentration of smoke without an added oxygen supply takes effect.
In a further embodiment, ~he above-mentioned assem~ly has a vent aperture provided in a portion of th wall of the duct spaced from the top thereof, e.g. a vent aperture disposed in a side po,rtion of the duct wall, and means are provided to move said closure means from said open position thereof to said closed position thereof when said combus-tion responsive contrcl means release the closure means when 3Q combustion is detected. Generally said means to move the closure means are provided with resilient means,acting on the closure means, which may therefore be spring loaded in some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

~ mbodiments of the invention will now be described by ~ay of example and with reference to the accompanying drawin~s in ~hich:~

.. ~ 6 -Figure l ~S a di~grammat~c plan view of part of a ~ullding struct~re f~tted with an air conditioning system;
Figure 2 is a dia~ammatic detail of a fire shunt located in the extract duct of the a~r conditioning system;
Figures 3 and 4 are perspective viewsof the fire shunt unit;
Figures 5A to C are diagrammatic views showing operation of the fire shunt of Figures 3 and 4;
Figure 6 is a diagrammatic plan view of a floor of an "open planl' design having air conditioning ~acilities;
Figure 7 is a diagrammatic sectional representation of an air conditioning duct section for use in a system accord-ing to the invention and shown in the free-flow position;
Figure 8 is a diagrammatic sectional representation of the duct of Figure 7 showing the flow diverting condition thereof;
Figure 9 is a diagrammatic perspective view of another duct section arrangement; and, Figure lO is a diagrammatic perspective representation 2~ o~ a further embodiment of a duct section in accordance with ~ the inve~*ion. c~

DETAILED DESCRIPTION

Referring to Figure l of the drawings, a building structure has a number of separate compartments, one of which is shown in Figure l and is designated by reference numeral (10). The building structure has an air conditioning system which includes a delivery duct (ll) and an extract or vent duct (12) which extend through each compartment. In each compartment branches of the main delivery and extract ducts may extend to separate inlet and outlet air apertures located at different parts in the false ceiling of the compartment. In some possible arrangements the space above the false ceiling containing the delivery duct, may itself comprise a portion of the extract duct system with connec-tions therefrom to the neighbouring compartments. Conditioned air is driven by a fan, represented diagrammatically by numeral (13) through the delivery duct which extends through 7 _ t~e ~uilding compartments and into the individual compart-ments through the inlets therein. Foul air from the compart-ments is extracted through the duct system~(12) by means of a fan diagr~mmatically represented by numeral (14), so as to maintain a pressure balance in the compartments.
In the system embodying the invention shown in the drawings, flow control devices, as illustrated in Figures 2 to 5, are located in the delivery and extract ducts. Flow control devices (15 and 16) are provided in the extract duct (12~ and delivery duct (11) respectively at positions in those lines adjacent where they pass out of the compartment (10) into the adjoining compartment through a fire proofed dividing wall (19). Flow control devices (17 and 18) are also provided in the delivery duct (11) and extract duct (12), respectively, at positions in the adjoining compart-ment adjacent the fire proofed partition wall (30) between the two compartments.
Referring to Figures 2 to 5, each flow control device comprises a vent aperture (20) in the upper part of the 2~ respective duct, or a duct section fitted in such duct.
A hin~e flap (21) is normally held to close the vent aperture by a releasable latching device (22), which for example ;~
comprises a la~tching member associated with a solenoid for ~ove~ent between a "latc~" position and an "unlatched1' p~sition. When the latching device (22) is in its "unlatched"
position the flap (21) drops to close the duct or duct section-to inhibit fiow therethrough and acts to divert such flow through the vent aperture (20) and back into the compart-ment (10~ ~rom which it came. Further constructional details of such a flow control device are given in Figures 7 to 10 which are described hereinafter.
A control system is provided for actuating the flow control devices (15 to 18). A smoke detector (23) may for éxample be provided and located either in the extract duct (12) adjacent the outlet flow control device (15) or at any other suitable place in the compartment. Indeed several such smoke detectors may be provided at strategic positions in the compartment. When the detector detects the presence of smoke it generates an electric signal which is communicated 3r~3 to the latching device (22) of flow control device (15) so that the flap becomes "unlatched" and drops to close the outlet of the extract duct to the next compartment. In so doing, the smoke and toxic fumes flowing along the extract duct are diverted through the vent aperture (20) back into the compartment (10). Electric contro] signals are also trans~itted to "unlatch" the latching mechanisms (22) of the flow control devices (16,17,18) in order to effectively seal off the compartment. In this way the further delivery of air to the compartment is also prevented so that the combus--tion taking place in the compartment tçnds to be stifled by the products of such combustion which are diverted back into the compartment.
Therefore on detection of combustion in the compart-ment, which very often will initially produce smoke which can be detected by any suitable known smoke detector, the outlet of the extract duct from the particular compartment is closed by flow control device (15) to prevent the products of the combustion being drawn out by the extractor fan (14) into other compartments of the building. The next step is to close the inlet of the delivery duct to the compartment by elosing flow eontrol device (17). This prevents further air being dri~en into the compartment by fan (13) which would tend to promote the combustion. The closing o~ flow control device (16) at the outlet of the compartment of the delivery duct prevents smoke and other combustion products passing into other compartments of the building through the delivery duct after the pressure of the excessive heat in the compart-ment (10) builds up suffieiently to be able to drive out such products through the pressurized delivery duct. The closing of flow eontrol deviee (18) at the inlet to the compartment of the extract duct similarly stops pressure in the compartment ~10) from forcing the combustion products back through the inlet of the extract duct to the compart-ment (10). The flow control devices (15 to 18~ do not need to be closed in sequence, but flow control device (15~ must be closed as quickly as possible after detection of combus-tion with the closure of the other flow control devices taking place simultaneously or subsequently.

It is possible although probably less desirable to operate a system as described above but using known types of flow control devices which do not incorporate a vent aperture for allow.ing a ready recycle of the products of combustion back into the compaxtment in which the combustion is taking place. ~~
In other embodiments the flow control devices ~15 to 18) may be controlled by heat responsive devices rather than from smoke detectors.
~0 In any of the constructions described above the closing of any one of the flow control devices.or indeed of the devices shown in Figures 7 to 10, which are described herein-after, can be used in conjunction with means, e.g.
electrically operated signalling means, to advise a control panel of the presence of combustion and in which particular compartment of the building and/or to sound an alarm.
A feature of the system described above is that if any of the flow control devices failed to close when triggered, the flow control devices in the adjacent aompartment should ~Q opera~e to isolate the products o combustion to those compartments.
The invention also provide~ systems adapted to take account of possible malfunctions of the individual flow control devices as described above for isolating a building compartment when combustion starts therein. Instead of providing a smoke de-tector only in flow control device (15), a smoke detector could be provided in each of the flow control devices (15 to 18), with control circuitry provided to receive signals from all the smoke detectors and to effect closure of all the flow control devices when a signal is received from any one or more of the smoke detectors.
In this way, failure of any individual smoke detector would not prevent closure of the flow control devices.
Furthermore the four flow control units of each compart-ment of the building structure, are linked in their owncircuit, and the circuits of adjacent compartments can be linked together and indeed cross linked to each and every other flow control unit in the building structure. In this way each and every flow control unit is linked to each and ~ r g~
- :LO - , every othe~ flow contro:L unit to provide a means of restrict-ing spread of the products of combustion throughout the building structure if there is a failure of one or more of the flow control units.
In systems in accordance with the invention where the flow control units of each compartment are not linked by an electrical control system so that closure of one unit effects closure of the other three units for that compartment, each flow control unit then operates individually. Such systems do not then effect a rapid cut off in the supply of oxygen to the compartment, since the flow control de~ice shutting off the supply of pressurized conditioned air to the compartment does not take place immediately following closure of the flow control device preventing venting off the products of combustion from the compartment through the extract duct.
In such systems, the vent apertures of the flow control devices, instead of communicating directly with the compart-ment to return the combustion products thereto, would be connected to pass such products outside the compartment into 2~ an extract passage or a respective such passage :Eor a group of compartments for venting outside the building structure.
This extract passage could be provided by a lift or other purpose made shaft fitted with an extract fan for opera-tion - during an extraction step. An electronic control system could be provided to detect closure of the flow control devices in the building. If this system detects that flow control devices associated with more than one compartment .7, are actuated indicating a failure of at least one such device in the compartment where combustion started, the

3~ system could send a signal to start the extract fan in at the top of the lift shaft to extract combustion products from each compartment or from each floor through extract ducts in each room which communicate directly with the lift shaft or any other separate extract duct provided at each floor. Alternatively the separate extract duct could discharge directly out of the building to the ambient atmos-phere at a preferred position at each floor.
~ eferring to Figure 6, a floor of a building structure has a central passageway (31), the walls of which need to provide a ~-hour fire delay, The "open plan" floor is then subdi~ided into individual compartments as required. The Rislng Builders Brick duct (32) for services normally has a

4-hour fire delay as should the construction around the lift shaft (33) and the stairways (34). The air condition system includes extract paths (35) and a delivery path (36). Flow control devices (37), as described above, are provided in the delivery and extract paths (36,35) as shown to pass the products of combustion, extracted through the air condition-ing system when there is a fire, either to the lift shaft (33) or the service shaft (32) or a purpose made vertical flue duct (38) inside or outside the service shaft.
Referring to Figures 7 and 8, an air conditioning duct 11~, e.g. either the delivery or vent duct of a system shown 15 i~ ~igures 1 to 6, extends through a partition wall 111 between two ccmparbmen~s 112, 113 of a building. me direction of air flow is shown by the arrows. The duct 110 is located in an aperture in the wall 111 by means of a sleeve 114 made of one or more sections of a load bearing and fire retardant material.
~he duct 110 has a vent aperture 115 in an upper part thereof and a hinged control flap 116 held to close the vent aperture 115 by a fusible link 109, e.g. a rivet or similar element made of a fusible material. The length of the flap is preferably equal to the depth of the duct. When the heat inside or outside the duct reaches the "control"
temperature the free edge of the flap 116 is released and the flap hinges downwardly to engage a stop 117 provided by ~7 a piece of angle iron or similar element located at the ~ottom of the duct, to close the duct. The flap could be longer;than the depth of the duct so that the stop 117 isnot required. The flap also acts to deflect the hot air and toxic fumes upwardly through the vent aperture 115, which is now open, as shown by the arrows in Figure 8.
The air moves under pressure of driving fans in the duct or by natural convection upwardly through the vent aperture so that smoke, toxic fumes and hot air are returned to the compartment 112 in which the conflagration started. The duct sealing arrangement described above can be built into standard duct sections or can be supplied as a separate flanged un~t f~r location intermediate along the length of a duct installation. The duct may be of ~arious different cross-sections, e.g. square, rectangular, round or "modified"
rectangular ducts which has rounded, outwardly projecting side walls. In the case of round or "modified" rectangular ducts it ~ill be necessary to provide a separate closure unit to be introduced in the duct system and fitted to adjoining "transformation" sections.
The system shown in Figure 9 is similar to that shown in Figures 7 and 8, except that the vent aperture in the upper wall o the main air duct 110 discharges into a connect-lng duct section 120 which extends a short distance upwardly of the duct 110 and then extends sidewards thereof to communicate at its outlet end with a vertical flue duct 121 extending through the building structure. The air ducting from each compartment of the building structure similarly communicates with the flue duct 121 which receives the products of a conflagration, e.g. toxic fumes, combustion particles and black smoke, in any compartment of the structure and discharges such products directly to the ambient atmos-phere, - In the arrangements of Figures 1 to 9, the vent aperture may be at the top of the duct and the closure means, in the ~orm of a plate, drops under gravity to its closed position.
There may be constructions where space above the duct is restricted, particularly if a central common outlet flue for all the building compartments is used requiring an '7 individual connecting duct section with the ~ent aperture -of each compartment. In such a situation a construction according to the present invention is preferable whereby a "side" position for the vent aperture can be employed.
Referrlng to Figure 10 the duct 130, which is of rectangular section, has a vent aperture 131 in a side wall thereof. The aperture 131 is n~rmally closed by a control flap 132 which is connected to the duct side wall by a spring loaded hinge 133 extending along a vertical side of the aEerture 131. The flap 132 is held in its position closing the ~ent aperture 131 by a fusible link, ~2~ 3 . - 13 -e.g. one or more rivets or similar elements 134 made of a usible material. Air flow is then permitted through the duct as shown by arrows X.
When the heat inside or outside the duct rises to a degree to melt the fusible link holding the flap open, the spring provided in the hinge assembly 133 acts to move the flap 132 to close the duct 130 and also to open the vent aperture 131. The heated air and fumes then flow through the vent aperture as shown by arrows Y. In its ~0 closed position the flap may be held against stops provided on the wall of the duct opposite to the~vent aperture.
However such stops are not required if the flap is made longer than the width of the duct. The continuing pressure of air assists in closing the flap and in maintaining the flap in its closed position, since the fans for driving the air along the duct would still be working.
~ n the embodiments of any of Figures 7 to 10, the closure plate or flap may be released by a latch member controlled by a control system as described above in relation to Figure 2.
2~

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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flow control assembly suitable for use in an air conditioning system having a duct comprising valve means pivotally mounted in the duct for movement between an open position in which it permits fluid flow through the duct and biased to a closed position in which position it inhibits such fluid flow, and vent means provided in the wall of the duct and positioned so that the valve means, in its open position, inhibits flow through said vent means and, in its closed position, the valve means inhibits flow through the duct while allowing substantially unrestricted flow through said vent means, said valve means being used in conjunction with one or more smoke detectors which, when activated due to presence of smoke, produce a signal to release a latching device holding the valve means in its open position, whereupon the valve means is free to move to its closed position.

2. An assembly according to claim 1 wherein the valve means are controlled by control means which are responsive to the presence of combustion.

3. An assembly according to claim 2 wherein the valve means are controlled by temperature responsive control means.

4. An assembly according to claim 3 wherein said temperature responsive control means is a fusible element.

5. An assembly according to claim 1 comprising a duct extending through a partition between separate compartments of a building structure for passage of air therebetween, valve means mounted in the duct, at a position adjacent the partition, for movement between said open position and said closed position, and control means to maintain the valve means in its open position which control means are responsive to the presence of combustion to release the valve means when combustion is detected, the valve means being adapted to move to said closed position when so released, to inhibit flow through the duct while allowing substantially unrestricted flow through the vent aperture.

6. An assembly according to claim 2, in which means are provided to move said valve means from said open position thereof to said closed position thereof when said control means release the valve means when combustion is detected.

7. An assembly according to claim 6 wherein said means to move the valve means are provided with resilient means acting on the valve means to move the valve means from said open to said closed position.

8. An assembly according to claim 5 wherein the duct communicates with a vent passage leading to the outside of the building structure.

9. An assembly according to claim 8 wherein said vent passage is provided with an extraction fan.

10. An assembly according to Claim 8 or Claim 9 wherein said vent passage is a lift shaft.

11. A method of controlling an air flow in a duct extending through a partition between separate compartments of a building structure, which comprises providing in the duct, pivotal valve means held in an open position permitting air flow through the duct and closing a vent aperture in a wall of the duct by control means which are actuated, when combustion is detected in one of said compartments, to release the valve means to close the duct to prevent products of combustion in one compartment from reaching another compartment and to divert such products through said vent aperture for return to said one compartment or for venting to the outside of the building structure.

12. A system for inhibiting the spread of the products of combustion from one compartment to another of a multi-compartment building structure, comprising closure means mounted in the air conditioning delivery and/or vent paths associated with each compartment of the building structure, and control means for respective ones of the compartments responsive to the presence of combustion in the compartment associated therewith to effect closure of at least one closure means for the affected compartment to isolate air flow to and from that compartment from the remainder of the compartments, said closure means being positioned to close at least one vent path at or adjacent the point where it exits from the compartment and said closure means being biased to a closed position for automatically closing when said control means are actuated.