CA1058946A - Means for retarding the spread of fire from a space in an environment isolating structure - Google Patents

Abstract

TITLE
MEANS FOR RETARDING THE SPREAD OF FIRE FROM A SPACE IN AN
ENVIRONMENT ISOLATING STRUCTURE

INVENTOR
Tibor Z. Harmathy ABSTRACT OF THE DISCLOSURE
A means for retarding the spread of fire from a space in an environment isolating structure, e.g. a building or a ship, comprises a duct system for conveying gases away from a fire in the space, an access gate operable to connect the space to the duct system, a fan for aiding the movement of the gases along the duct, and a means for opening the gate and starting the fan when a fire occurs in the space. The cross-sectional area of the duct system is related by formulae to the area of air intake to the space and the pressure head to be de-veloped by the fan in order to i) drain away smoke and flames from the space containing the fire, ii) produce a depression in the space and thereby prevent the flames and smoke from entering any neighboring spaces, and iii) draw sufficient air into the space to ensure relatively low fire temperature and a relatively short fire duration. Preferably a release.
gate isolates the exit end of the duct system from the out-side atmosphere until a fire occurs in the space.

Description

1~3S~3~4 .
Thls invention xelates means for retardiny the spread of fire from a space in an environment isolatincJ structure.
In U.S. Patent No. 3,955,3~3, dated May 11, 1976, "Means for Retarding the Spread of Fire from a Building Space", T.Z. Harmathy, a fire safety system is described, referred to as "ire drainage" ~ystem which, once a fire passed its inci~

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pient stage, checks any further spread of fire and smoke in the building by performing the following function~ "drai ning" the flames and smoke away, through the "drainage ducts", ~ -10 from the building space on fire, ~ii) producing a depr~ssion in that space and thereby preventing the flames and smoke from entering the neighbouring spaces, and (iii) drawing sufficient air to that space to ensure relatively low fire temperature and relatively short fire duration. By these functions the system confines a fully developed fire to the space of origin and mi-nimir~es the fire damage even without human intervention.
The main advantage of the abo~e mentioned fire drai-nage system, herelnafter referred to as the "natural drainage `~
, system", is that in the most advantageous form of operation it 20 does not rely on the availability of ser~icas, water and elec-~tricity. However, its disadvantage is the rel~tive inflexiki~
,, : ~,, lity of the design and routing of the drainage ducts. ;
All components of the~natural drainage system have been describad in U.5~ Patent No. 3r955~323~ The dxainage ducts have been described as up~.~ardly extending means, having poor heat transmitting walls, for connecting the building spaces with the outside atmosphere, preferably above the roof level. Their function in fire has been described as three fold: (i) théy provide safe passages for t~e flames and smoke 30 leaving the buildiny space on fire, (il~ they ~ring about a long column of hot gases the potential ene-rgy of which is ex- ;~

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plolted in crea-tinc3 a depre~sion in that space and thexeb~ .
prcventing the flames and smoke from spreading to the neigh~
bouring spaces, and (i.ii) the potential energy of the hot qases in the drainage ducts is also exploited in drawing to that space air at a rate necessary to keep the fire temperature relatively low and the fire duration relatively short.
Naturallyt to create in the space containing the fire a sufficiently large depression capable of ensuring the :
planned operation of the system, the movement of the fire ga~
10 ses in the drainage duct must not be greatly hampered in order : .
- to keep the loss of mechanical energy of gases between the space on fire and the outside atmosphere less than their gain `~
in potential energy. .
While the natural drainage system is undoubtedly . .
a useful contrihution in dealing with fires in buildings, .
to minimize the loss of mechanical energy, the cross-sec-tional area of the drainage ducts must be selected relati- ..
vely large, usually amounting to 1 to 5 per cent of the floor '`~
area. Also, the routing of the ducts must be kept airly . ~ ~
20 simpIe, pre~erably as straight as possible and as vertical ;~
as possible throughout, because directional and cross~
sectional changes greatly increase the energy loss.
Selecting large cross sectional areas and simple routing for the drainage ducts may be especially important with lower buildings, say up to 4 storeys high, since in such cases the length of the drai.nage ducts is relatively small `~
and, therefore, the gain in the potential energy of gases along the ducts i5 relatively low. The applicant has now found that in order to avoid the need for large duct areas or ... -~
30 to allow more fle~ible routing of the ducts, or both, it is often advisab].e, especially for lower buildlng~ or o-ther in~

- 2 -,. ~ ., ~, ~ .

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hercntly sh..-llow constructions, such as sh.ips, to supplement the gain in potent:ial energy of the hot gases in the ducts by external energy supplied conveniently by an exhaust fan~
It is an object of some embodiments of the present -inven-tion to provide a ~ire drainage system, hereinafter re--ferred to as an "assisted dxainage system" which facilitates a more economical use of the interior of shallow dwellings and offers a greater flexibility in the routing of the fire ~:
drainage ducts for any type of environment isolating structure. .
In this specification "env~ronment isolating struc-ture" includes immobile stxuctures such as immobile residen-tial institutional, assembly, business, mercantile, industrial, or storage facilities such as buildings, and mobile structures : .
such as mobile facilities for any of the above purposes such ~ :
as for example, ships and mobiles homes. ~ :
According to the present invention there is provided a means for retarding the spread of fire from a space in an environment isolating structure, having means for facilitating air intake to the space when it.contains a fire, comprising~
a) duct means for connecting the space to the out~
side atmosphere, the duct means having poor heat transmitting .;
walls along any portions which are adjacent any heat damagea~
ble material, b) closure means, tightly closing and thermally in~ `;
sulating the space from -the duct means, ;;
c) means urg.ing the closure means to open and there~
by establish connection between the space and the duct means, d) securing means, releasably securing the closure ~ :
means in the closed positi.on, e) yas propelllng means for assisting the movement of fire gases along the duct means from the space,

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~35~ ~ ~ 6 f) actua-tiny m~ans Eor actuatiny the gas propelliny :;
means, when the space contains a :Eire, and wherein g) for most efective operation the following two conditions are satisfied when the space considered con~
tains a fire, relying on the state of the art:

AC ~ l r1Pd r Z Pa-P
AD 1.163~ ~2~ Pe L g(Pa Pd~ Pe ~~ P ~ P ~ P

~Pm _l 10 + Pe and Ac~ [ 2Pe (Pe ~ P)~ -C~G ~ l where AC (m2) is the area of the effective opening through which air is allowed to enter the space considered wnich contains the ~:~
fire, .~ :
AD ~m23 is the cross-sectional area of the drainaye duct, 20 ~ ~dimensionless) is a factor characteristic of the air~
tightness of the drainage duct, -.
~ (dimensionless) is an orifice ~actor characteristic o~ the sizes of the effective opening, : : ~ (dimensionless) is a factor describing, in terms of velo-city head, the loss of mechanical energy at the entry and exit of fire gases to and from the drainage duct, ~llat asso~
ciated with the presence of flow--alter.ing duct sectlons~ and ..

that brought about by the friction of gases alony the duct surfaces, ;~
30 g (m/sec2) is the acceleration due to gravity, .
Pd (ky/m3~ is the averaye density of fire yases in the drai~
naye duct,

4 r ,~ , 4~i ~

Pe (kg/m3) is the density of air in the space Erom which it enters the space considered, ~ ~
Pa (kg/m3) is the density of the outside atmosphere, ~-z (m) is the elevation of the exit end of the drainage duct . ~ :

above the mid-height of the space considered, .
:-'- .
Pe (kg/m s2) is tlle pre5sure of air in the space from which it enters the space considered, Pa (kg/m s2) is the pressure of the outside atmosphere, p (kg/m s2) is the desired pressure in the space, and is se-10 lected as equal to or lower than the pressure in any adjoining A~space which is to be protected from the penetration of flames and fire gases, ~Pm (kg/m s2) .is the pressure head to be developed by the ex~
ternal energy source, namely by the means for assisting the movement of fire gases along the duct me2ns, .
C (kg/m2s) is a constant characterist~c of cor~ustible ma-terials in the space considered, (m2Jkg~ is the specific surface of cor~ustible materials in the space considered, and - ~
20 G (kg) is the total mass of combustible materials in the :~ :
space considered, whereby : h) in the event of a fire`in the space considered :~
~the securing means releases the closure means and allows the .-~
means~urging the closure rneans to move the closure rneans and : connects ths space with the duct means, and the actuating means ~:
actuates the gas propelling means to assist movement of ~ire gases along the duct means, so that the gas propelling means .ih conjuctlon with the air intake, and the duct means jointly (i) drain away flames and smo]ce from the fire, ~ ;
30 (ii) produce a depression in the space considered, thereby retarding the spread of fire, and . _ 5 _ ~ :

' ., ~

~ 8~6 (iii) dra~ s~lfficient air to the space considered to ensure relatively low ~ire temperature and relatively short fire du- ~ -ration. :~ :
In some en~odiments of the present invention the .
space considered is one of a plurality of spaces in the envi~
ronment isolating structure, the duct means is for connecting each space to the outside atmosphere, the closure means is one of a plurality of closure means for each space, the means urging the clo~ure means is one of the plurality of urging 10 means for each space, the securiny means is one of the plura-lity of securing means for each space, whereas the actuating means for actuating the gas propelling means may either be one of a plurality of actuating means for each space, or may be one serving the plurality of spaces.
In other embodiments of the present invention there ~ -is provided at least one release gate closing the exit end of .
the duct means from the outside atmosphere, and release gate ,opening means for opening the release gate or gates. ' In other embodiments the securing means is a heat .~
20 destructible~member to be destroyed by a fire in the space ;. ...... ;
considered, thereby allowing the closure means to open.
In yet other embodiments -the release gate opening `~
means includes a heat destructible member holding the release gate closed and capable of being destroyed when fire gases pe~
netrate the duct means, to allow the release gata to open. .
Other embodiments having a plurality of spaces in-clude a release gate closing the exit end of the duct means from the outside atmosphere, which opens when ~ire gases .
enter the duct means from any of the spaces.
Being different from the na-tural dra:Lnage system :-~
mainly in the size and routing of the drainage ducts and in - 6 ~ - ~
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-the supp].y o:~ ex-te:cnal ener~y, many of the components of the ass:isted dra.inage system accordin~ to the present inven-tion ~.
are similar to those descri~ed w.ith reference to Figs. 1 to 6 :
of U.S. Patent No. 3,955,323. Some e~odiments of the present invention may be regarded as supplementary to that contained in U.S. Patent No. 3,955,323.
Because of the greater flexibility in the routing of the drainage ducts, with the assisted drainage system ~:~
according to the present invention, the ducts may com~
10 prise horizontal sections. Yet, from the point of view of producing a gain in the potential energy of the fire gases, which is exploited in the planned operation of the sys~
tem, only the upwardly extending sections are effective.
In an article published in 1948, entitled "A Method :~
of Fire Control" (Transacti.ons of the American Society of Hea~
ting and Ventilating Engineers, Vol. 54 (1948), pp. 59 to 70) :
A.C~ Bartlett described a system w~ich may at first glance ~:
. appear to resemble the assisted drainage system. While the essential differences between Bartlett's system and the assis~
20 t d drainage system will be self evident after reading the ; :
followin~ description with reference to the accom~anyiny:dra- :
w.ings, it is convenient to point out at this stage that Bart~
le-tt's system cannot be a version of an assisted ~rainage ;`~
system because~
(i) Bartlett's system was vlsualised as a method of ~ :
tempoxary confinement of a fire (more exactly: smoke) "until the fire department arrives" (p. 59~ In cont.ra.st, the pre~
sent i.nvention hcis be~en devised to confine fully developed fires without human intervention while it consumes all com~
30 bust:i.bles in the space (ii) Bartlekt's method i.s, .in effect, a method of , . . ., , . ~ .
.. , . . . ,: . . -~i8~4t:~

control of the move~en-t o~ srnoke produced ~y incipient fires, and not to keep the fire temperature relatively low and the fire duration relatively short, which is achieved ~ith the :~
present invention. The intent of the method provided by Bart-lett is clearly reflected by the fact that in his supporting experiment Bartlett used only very light fire load and smoke ~ombs (p. 67). It is also reflected b~ the constructional de~
tails of the experimental set-up~ The narrow "slots" in the barrier ducts (Figure 1 of the re~erenced paper) are insuffi- . :~
10 cient to admit, without intolerabIy ~igh pressure losses, the `~
amount of smoke produced by a fully developed fire, and the ducts to carry other than highIy diluted gases at temperatures only slightly above the normal room temperature. In contrast~
the fire drainage ducts of the present invention are properly ~ :
dimensioned and de.signed to handle the large flow of flames and hot gases produced by a fully developed fire, at tempera~
,.... ~. .
ture 300 to 1100C above the room temperature.
~iii) Bartlett.'s method was devised explicitly i~
for reducing the possihility of vertical spread of flames and 20 smoke along stairways, elevator ~hafts, and escalators. To !~
achieve this, a "downdraft" is used (p. 63) across the opening ~ ~:
to ~e protected, presumably sufficient to prevent the rise of :
smoke to the upper storeys. In contrast, the present inven-tion relies on the creation of a depression in the space on fire/ which is capa~le oE preventing the spread of flarnes and ~ ~ ~
smoke either horizontally or vertically. The present invention :.
is applicable to an~ type space in an environment isolating structure e.g7 rooms, uncompartrnented space3, and corridors. ;:
iv) Bartlett's system uses a water curtain around 30 the wellway (p. 59, p. 67) and thus ties the operation of the ~.- ?
system to the availability of water at the time of fire. In . - 8 ~ :

ontrclst, the present invenl::ion does not rely on the availa--~i.lity oE water in the confinement of fire.
(v) Bartlett's method was suggested in the late 1940's when very little was known about building fires. The des~gn of his system is essentially based on the assumption of a downdraft velocity of air, about 1O5m~s, in the opening ~o ~e protected. Simple claculations have revealed that this velocity may be grossly in error, dependent on the temperature difference between the inside of the building and the outside ~ :~
10 atmosphere, the height of the building, the storey of the fire, and several other factors. In contrast, the assisted fire drainage system according to the present invention has been ~ :
developed from knowledge accumulated during the past twenty years on the characteristics of compartment fires and on the `~
pressure distribution in buildings, as interpreted and summa- . . ;
rized in a number of the papers by the applicant, e.g. "A ~ ~
.
New Look At Compartment Fires, Parts I and II", (Fire Techno- .
logy 8, 196, 326 (1972), "Design of Buildings for Fire Safety, Parts I and II" [Fire Technology 12, 95, 219 (1976).
~0 In the accompanying drawings which illustrate, by way of example, embodiments of the present invention~
Fig~ 1 is a perspective view o a "vertically bran- `~
ch.ing" arrangement of an assisted drainage system, as applied to the rooms and corridors of a hiyh-rise office building, Fig. 2 is a sectional side view showing the fire :
clrainage duct and the various means of effectinc3 its opera~
tio~
FiCJ. 3 is the perspec-tive view of a "horizontally branching" arrangement of an assi.sted drainage system .or the 30 .room~s and corridors of an office building sim:ilar to that shown :;n Figure 1, ..

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Similarly -to th2 natural drainage system, the opera--tion of the present inven-tion is based on a coordinated with-drawal of flames and smoke from, and admission of air to the space containing the fire. Thi~ operation is accomplished partly by exploiting the thermal energy provided by the fire itself, and partly by the consumption of external energy. The thermal energy of the fire and the external energy are combined to achieve the following functions:
1. Withdrawing the flames and smoke from the space 10 containing the fire in a safe and organized manner.
2. Producing a depression in that space and thereby preventing the flames and smoke from entering any of the neigh~
bouring spaces.
3. Drawing air into that space at a rate sufficient -~ -for producing relatively low fire temperature and relatively 3hort fire duration.
The design procedure for embodiments of the present invention such as the embodiments shown in Figs. 1 to 3 is ba~
sically similar ~o that to be followed with the natural drai~
20 nage system, as described in U.S. Patent No. 3,955,323. Again, two conditions must be satisfied, one of which is iden~ical with that in the patent~

AC~ r2 Pe (Pe ~ P~
C ~ G ~7 1 l'he other is also similar to that yiven in the patent, but con~
tains an additional term which xepresents the input of exter- ;~
nal energ~ in the form of the pressure head developed by gas propelling means, such as,~for example, an exhaust fan: ;

AC ~ 1 J 1 Pd I g(p - P ) ~
30 AD 1.163~ l2~ Pe L a d Pe ~ P Pe P ~;

~Pm 1~
Pe ~ P~J
- 10- ~ ' ~

, : . ,,, , , ':

~58~
where AC (m2) is the area of the efEec-tive opening through which air ~.
is allowed to enter the space considered which contains the fire, AD ~m2) is the cross-sectional area of the drainage duct, ~ (dimensionless) is a factor characteristic of the air-tight- .
ness of the drainage duct (equal to 1 if the duct is complete~
ly air-tight, larger than 1 if it is not), ~ (dimensionless) is an orifice factor characteristic of the ---- 10 sizes of the effective opening (usually amounting to about 0.7), - : :
~ (dimensionless) is a factor describing, in terms of veloci- ~
ty head, the loss of mechanical energy at the entry and exit ~ :.
of fire gases to and from the drainage duct, that associated with the presence of flo~-altering duct sections (for example, :
elbows, diffusers, sudden expansions, etc.) and that brought ~:
about by the friction of gases along the duct surfaces, g (m/sec2) is the acceleration due to gravity, .
Pd (kg/m3) is the average density of fire gases ln the drai~
nage duct, 20 Pe (kg/m3) is the density of air in the space from which it ~ ~ :
; .
enters the space considered, Pa (kg/m3) is the density of the outside atmosphere, z (m) is the elevation of the:exit end of the drainage duct above mid-height of the space considered Pe (ky/m s2) is the pressure in the space from which air en~
ters the space considered, Pa (]cg/m s2) is the pressure of the outside a-tmosphere, p ~kg/m s2) is the desired pressure in the space containing t.he fire r and is selected as equal to or lower than the pres-30 sure in any adjoining space which is to be protected from thepenetration o:E flames and fire gases (for example, equal to or . :. . : . :,. ::: . : : ::

1CP58~34~ ~
lower th~n t~e corriclor pressure if the space conta.ining the fire is a room acljacent a corridor), aPm (kg/m s2) is the pressure head to be developed by the ex--ternal energy source, such as, for example, by an exhaust fan, C ~kgjm2s) is a cons-tant characteristic of the combustible materials in the space considered (for mainly cellulosic fuel it is approximately 0.038), 0 (m2/kg~ is the specific surface of the combustible materials (for conventional furniture it is usually between 0.12 and 10 0.18) in the space considered, and ~-G (kg~ is the total mass of combustible materials in the space considered. i `~
The operation of the assisted fire drainage syst~m is described with reference to Figs. l and 2 for rooms and corridors in a building but is equally appiicable to other ~
environment isolating structures such as, for example, ships. ~ -In Fig. 1, spaces in the form of fivè rooms are shown~ Rl to R5, and a T-shaped corridor, CT, on the ground floor of an eleven-storey office building. Vertical drainage 20 duct means DVl, serves rooms Rl and R2 through closure, urging and securing means in the form of access gates Gl ~nd G2. Ver~
tical drainage duct means DV2 serves rooms R4 and R5 through closure urging and securing means in the form of access gates G4 and G5. Vertical drainage duct means DV3 serves room R3 ~ -and the T-shaped corridor CT through closure urging, and secu-ring means in the form of access gates G3 and G6. The upper -ends o~ the vertical drainage duct means DVl, DV2 and DV3 are ` -connected abov~ the roof level of the building l by a hor.izon--tal duct sect:ion, DH, which has an outl.et to a gas propelling ~
30 means in the form of an e~haust fan F driven by an electric ~ :
motor M. Release gat-e GRl and GR2 are located at the top of a - 12 ~

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:.,, : : : . : . . . .. - . . .

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diffuser which i~ emplo~ed to reduce the exit loss of mecha-nical energy oE fire gases leaving the exhaust Ean F.
In the embodiment illustrated in Figure 1, the actua-ting n;eans consist of three heat or smoke sensors, DTl, DT2, and DT3, located inside and at the top of each vertical drai-nage duct DVl, ~V2, and DV3, as shown.
The vertical drainage ducts, DVl, DV2 and DV3, are made with walls of poor heat transmitting characteristics, for ~ ' , example with heat insulating walls, in order to prevent damage lO by heat transmission to any heat damageable material in any ~, space adjacent the drainage duct. The wall of the horizontal duct section ~H needs no insulation because it is not adjacent any heat damageable material. This duct section eliminates the need for three exhaust fans, such as F, t'nree motors such as M and three or more release gates such as GRl and GR2. ,~
As shown in Fig. l, all building spaces that are lo~
cated above one another have a,ccess gates to the same vertical drainage duct means. If fire breaks out in any space, only the access ga~e of the space containing the fire will open.
20 There are various possible designs of the access gates Gl to '~
G6 and various ways of achieving the opening of these gates in response to fire. A sim~le and reliable way,of opening the access gates Gl to G6 is by having the securing means made from a heat destructible material that holds the closing means, the yate itself, closed against its own weight, which can be identified in this case with the urging means. The heat of ~ ~
the fire destroys the closing means and causes the gate to -, open. It can also be arranged that the energy of fire be re~
lied upon in th~ opening of the release gates GRl and GR2.

30 SLnce, 'nowever, the o~eration of the assisted fire drainage system entails the availability of electrical energy at least - 13 - ' ''' .~,, ,I.JJ

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;, ' , . , ' ' ' ' , .

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at the roo~ level for energizing the elecl-ric motor M, it seems more practical to have the release gates Gr~l and Gr~2 open by an elec-trical device at the top of each vertical drainaye duct. -In the embodiment shown in Figure 1, the opening of the release gates GRl and GR2 and the energisiny of the ~ ;
electrical motor M is triggered by an electrical signal pro~
duced by one of the heat or smoke sensors DTl, DT2 or DT3, ins~
talled at the top of each vertical drainage duct DVl, DV2 and DV3.
If the a~ailability of electrical power can be relied 10 upon throughout the building 1 during a fire, it can also be -~
arranged that the opening o~ the xelease gates GRl and GR2 and . .
~he energisation of the electric motor M be caused by an elec~
trical signal received from a heat or smoke detector located in the space containing the flre, or produced by the opening ;
of the access gate. -Figure 2 shows a drainage duct 2, with suitable access gates 4 and 6 and release gates 8 and 10, which may be ~ ?~
used in the embodiment shown in Figure 1.
The walls of the drainage duct 2 are provided with ;~
20 suf~icient thermal insulation so that the walls have poor heat transmitting properties and thus prevent damage by heat trans~
mission to spaces located on floors above the space containing ;;~
the fire. In Figure 2 the -thermal insulation consists of a layer of some heat-resistant insulating material 12, for exam~
~ .
ple, sprayed~on asbestos or alumina-silica fibers, securely attached to a lightweight concrete base 14. In other embodi- `~
ments, double-walled light metal ducts, filled with water bet-ween the walls arc used. `
.. ~ - .
For obvious reasons, it is desirable for the access 30 gates 4 and 6 to be opened by the fire itself. The access gates 4 and 6 shown in Figure 2 have the desirclble feature that . '' . ~, ' ~58~4~i their activation does not depend on the availability of elec-tric power at the time or in the area of a fire. In Figure 2 the access gates 4 and 6 and t'he release'gates 8 and 10 are shown in closed position~ The access gates 4 and 6 consist .' of closure means in the form of two sepaxately openable panels ;' 16 and 18, both attached to a gate frame 20 hy hinges 22 at -the lower edge of the gate frame 20. The outer panel 18 has ~ -thick thermal insulation 24 to thermally insulate the space .~ .' outside the gate'assembly from heat when the drainage duct 2 10 is fil~ed with hot gases originating from a fire at a lower floor level. Both'the inner and outer panels, 16 and 18 res- :
pectively, are sealed to the gate fr~ne 20. An outer seal ~6 for panel 18 may be made from a moderately he'at-resistant ma~
terial, while an inner seal 28, for the panel 16 can be of any ~ ':
ordinary sealantO The inner panel 16 is locked to the inside rim of the gate frame 20 by J-shaped studs 30 and nuts 32 or other fastening elements, made from a heat destructible mater-rial such as a low-melting alloy or a combustible material.
The J-shaped studs 30 and nuts 32 form securing means, relea-20 sably securing the closure means, panels 16 and 18, in the clossd posi.tion. The nuts 32 are preferably thermally insula- :~
ted from the inner panel by thick washers 34 of, for example, a plastic material. A spring 36 is compressed between the .~
inner and outer panels 16 and 18 respectively, and forms the ~:
means urging the closure means i.n the form of panels 16 ana 18, '~: .
;~.
to open and thereby establish connection between the space and the duct means or dxainage duct 2~ The panels 16 and 18 are '`
connected by a wire cable 38 which'will prevent them from se~
.. , .: .
parating by more'than a predetermined angle. Instead of spxing 30 36, the u~ging rneans may.consi:st of a.counter-~elcJht or the ;~
weigh.t of the''mner pan~1; 16 itsel'f. '~ ~' . ~--- 1~ -- , .

~' .. - .. . .

In o~exation, as a ~ire builds up in the space, the ;~
fastening elements in the form oE nuts 32 melt or burn and -cause the spring 36 to swing open the inner panel 16 which, in turn, pulls the outer panel 18 open by the wire cable 38.
Another possible, but less desirable, method of ha~
ving the access gates to open was described in connection with Figure 6 of U.S. Patent No. 3,955,323.
The closed access gate 16 can be made inconspicuous by, for example, being covered with wall paper. It is prefe~
10 rable, however, that the cover to the access gate 16 be bright-ly coloured or labelled to remind occupants that this area -~
must not be blocked by furniture or any other obstruction. i~;
The types of access gates discussed so far were de- ~ -vised for activation by the fire itself. Sometimes it may seem desirable to have the release gates activated electrically, hydraulically, pneumatically or otherwise by a signal received . .
from a heat or smoke detector, or to activate them at will manually, electrically, hydraulically, pneumatically or other~
~ise. -The hot gases leave the fire drainage duct through one, twol three or four release gates of identical design such as release gates 8 and 10. The release gate assemblies 8 and 10 in Figure 2, each consist of a frame 40, and a double-walled gate panel 50, attached to the frame 40 by hinges 51 and sealed to the frame 40 by an ordinary sealant 52. The gate panel 50 ~
is locked by a small lever 53 held in the locking position by ~;
a U~shaped tongue 54 and by the pulling force of heat destruc~
tible line 55 which may be made of a low-melting or combusti-: : .
b:Le material. A small spring 56 urges the tongue 54 from bet~

30 ween the c~ate panel 50 and the lever 53 in a direction for the lever 53 to clear the frame 40. A pull on the line 55 is exer- ;

16 ~
'.'" ,. ": :"' ` 1~35~9~ ~

-te~l hy a t~nsion ~p.r.ing ~2 and an electrical heatincJ coil 4 is pxovided around a por-tion of the line 55. In the embodi-ment shown in Figure 1, an electrical signal produced by any of the heat or smoke sen~ors, DTl, DT2, or DT3, will cause the switching on of the heating coil 44. 'rhis in turn will cause ~ :
the tensioned line 55 to break, and allow the spring 56 to pull the tongue 54 from between the gate panel 50 and the le--ver 53. l'he gate panel 50 then falls open by its own weight. ~;
Simultaneously with the energization of the heating coil 44, 10 the signal from one of the heat or smoke sensors, DTl, DT2, or DT3~ al.so energizes motor M to drive fan F and assist in drai- ~
ning away the fire from the space on fire in a manner previ- :
ously described.
As mentioned, othex less desirable methods of ope- ;
ning the rel.ease gates, GRl and GR2 in Figùre 1, or 4 and 6 in Figure 2, and setting the motor M and exhaust fan F (in "
Figure 1) in operation are also possible. Thus, these opera-tions may be tri.ggered by signals from heat or smoke sensors -~
located in all protected spaces, or by signals produced by 20 the opening of any one of the access gates, such as gates Gl to G6 in Figure 1 or yates 4 and 6 in Figure 2.
. It may be added that the use of release gates is not a5solutely necessary. The top end of the drainage duct system ~ ~
~a~ be left open if the openings are satisfactorily protected ~ ;
against precipitati.on and dirt.
: . .. ~ ;
In designing th.e fire drainage ducts and gates~ a de~

sirable conside:ration is to make the system reusable without repair, excepting the relea.se gates and the access yates di~
rectly involved i.n the fi.re.
The vertically branching embodiment of the assisted drain-lge system can also be adoptecl to the uncompartmented .,, , ' ` ' .
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spaces of ~he bui].dillg. The arranc;ement of the drainage duc-ts, fan and r~lease gate will be similar to that shown in Fiy. 1.
Naturally, the number of vertical drainage ducts served by one exhaus-t fan and release gate may be ~ither less or more than three.
The vertically branching embodiment of the assisted drainage system shown in Figure 1 does not allow much flexibi- ~ :
lity in the routing of the vertical drainage ducts, but ~llows the selection of suitably small cross-sectional areas for the 10 drainage duct means in relation to the total floor areas.
In Fig. 3 similar parts to those shown in Fig. 1 are designated by the same reference numerals and the previous text . `~
is relied upon to describe them.
. :
Fig. 3 shows a horizontally branching embodiment of the assisted drainage system, as applied to the rooms and ;
corridors on the first floor of an eleven-storey office buil ding identical to that shown in Fig. 1. A single vertical drainage duct, DV, serves now all rooms and corridors in the building, via eleven horizontal drainage ducts such as hori~
29 zontal duct DH. The access gates are located on the underside ~
of the horizontal drainage ducts such as drainage duct DH. .~;;; ;
Access gates G7 to Gll serve rooms Rl to R5, respectively, and ~ ;
access gate G12 serves the T-shaped corridor, CT. Since the .,., ~, .
horizontal drainage ducts such as horizontal drainage dwct DH ;~
~.. . . .
can be conducted in the ceiling space, only the vertical drai~
nage duct DV occupies useful building area. This solution al~
i50 offers the advantage of allowing the access gates G7 to G12 to be located on the ceiling where their presence puts less restriction on the furnlture layout. Where the horizontal :
30 drainage ducts such as horizonta]. drainage duct DH and the vertical drainage duct DV are adjacent any heat damageable -- ~.8 - :

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matel-ial tl~ir ~alls must be o:E poor heat transmitting cllarac-teristics.
The exhaus-t fan, F, and the release yates, GRl and GR2 are located above the roof level.
The embodiment shown in Fig. 3 may be found to be less favorable for some environment isolating structures con-taining mainly large uncompartmented spaces.
The solutions for the opening of the access gatesG7 to G12, the release gates GRl and GR2, and the setting of .. 10 the exhaust fan F i~ operation by energizing electric motor M
require the availability of electricity at several or many points of the building 1. Possible solutions include the uti~
lization of an electric signal produced by heat or smolce sen-sors located at strategic locations in the fire drainage duct system or in all building spaces, or by a signal produ~ed by -~
the opening of any of the access gates, such as gates G7 to .
G12 which may be similar in construction to these shown in .
Fi.gure 2, except, of course, they are now arranged horizontal~
ly. Having the access gates opened by the heat of fire in .~;~
20 the affected space, as described with reference to Fig. 2, has ~;
advantages, but a designer may choose to activate the access gates such as gates G7 to G12 electrically.as described in `~
connection with Figure 6 in U.S. Patent Wo. 3,955,323~ Many other solutions will readily occur to those skilled in the art.
Combining the vertically and horizontally branching draillage ducts embodiment of the assisted drainage system wi~
thin a singl.e dwelJ.ing is possible.
While the two ernbodiments of the present inventi.on which have been described with reEerence to Figs. 1 to 3 re- ~:
3Q late to an eleven-storey building, that is, to an immobi.lc .
fa~.iJ.ity, it is obvious that the invention is also useful for -- 19 ~

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~5~3~46 other envirorlm~nt i~olcltin~ .;tructures such a.s mobile faci-lities, for ~xample, ships and the l.ike. ~ ~ ~
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Claims (5)

CLAIMS:

1. Means for retarding the spread of fire from a space in an environment isolating structure having means for facilitating air intake to the space when it contains a fire, comprising:
a) duct means for connecting the space to the out-side atmosphere, the duct means having poor heat transmitting walls along any portions which are adjacent any heat damagea-ble material, b) closure means, tightly closing and thermally in-sulating the space from the duct means, c) means urging the closure means to open and there-by establish connections between the space and the duct means, d) securing means, releasably securing the closure means in the closed position, e) gas propelling means for assisting the movement of fire gases along the duct means from the space, f) actuating means for actuating the gas propelling means, when the space contains a fire, and wherein, g) for most effective operation the following two conditions are satisfied when the space considered con-tains a fire, relying on the state of the art:

and where AC (m2) is the area of the effective opening through which air is allowed to enter the space considered which contains the fire, AD (m2) is the cross-sectional area of the drainage duct, ? (dimensionless) is a factor characteristic of the air-tight-ness of the drainage duct, .delta. (dimensionless) is an orifice factor characteristic of the sizes of the effective opening, .alpha. (dimensionless) is a factor describing, in terms of velocity head, the loss of mechanical energy at the entry and exit of fire gases to and from the drainage duct, that associated with the presence of flow-altering duct sections, and that brought about by the friction of gases along the duct surfaces, g (m/sec2) is the acceleration due to gravity, ?d (kg/m3) is the average density of fire gases in the drai-nage duct, ?e (kg/m3) is the density of air in the space from which it enters the space considered, ?a (kg/m3) is the density of the outside atmosphere, z (m) is the elevation of the exit end of the drainage duct above the mid-height of the space considered, Pe (kg/m s2) is the pressure of air in the space from which it enters the space considered, Pa (kg/m s2) is the pressure of the outside atmosphere, p (kg/m s2) is the desired pressure in the space, and is se-lected as equal to or lower than the pressure in any adjoining space which is to be protected from the penetration of flames and fire gases, .DELTA.pm (kg/m s2) is the pressure head to be developed by the ex-ternal energy source, namely by the means for assisting the movement of fire gases along the duct means, C (kg/m2s) is a constant characteristic of combustible mate-rials in the space considered, ? (m2/kg) is the specific surface of combustible materials in the space considered, and G (kg) is the total mass of combustible materials in the space considered, whereby h) in the event of a fire in the space considered the securing means releases the closure means and allows the means urging the closure means to move the closure means and connect the space with the duct means, and the actuating means actuates the gas propelling means to assist movement of fire gases along the duct means, so that the gas propelling means in conjuction with the air intake, and the duct means jointly (i) drain away flames and smoke from the fire, (ii) produce a depression in the space considered thereby re-tarding the spread of fire, and (iii) draw sufficient air to the space considered to ensure relatively low fire temperature and relatively short fire duration.

2. Means according to claim 1, wherein the space is one of a plurality of spaces in the environment isolating structure, one above another at different floor levels, the duct means is for connecting each space to the outside at-mosphere, the closure means is one of a plurality of closure means for each space, each closure means has means urging the closure means to open and thereby establish connection bet-ween that space and the duct means, and securing means, re-leasably securing the closure in the closed position.

3. Means according to claim 1, which includes at least one release gate closing the exit end of the duct means from the outside atmosphere, and actuating means for opening the release gate or gates when fire gases enter the duct means.

4. Means according to claim 1, wherein the securing means is a heat destructible member to be destroyed by a fire in the space, thereby allowing the closure means to open.

5. Means according to claim 2, which includes at least one release gate closing the exit end of the duct means from the outside atmosphere and actuating means for opening the gate or gates when fire gases enter the duct means.