US3926101A

US3926101A - Fire safety systems

Info

Publication number: US3926101A
Application number: US483818A
Authority: US
Inventors: Cyril H Moss
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-06-26
Filing date: 1974-06-27
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: GB1438001A; DE2430592A1

Abstract

This invention relates to systems for clearing smoke from buildings when a fire occurs therein. Smoke detectors are provided in communal units in the building and means are provided to admit air under pressure to the communal units when smoke is detected. At the same time self-closing fire-stop doors are closed to restrict passage of smoke between the communal units. When air conditioning is provided in the building by fans which admit and extract air the extraction fans are controlled by the smoke detectors so that they are reversed when smoke is detected. The speed of operation of all fans may also be increased when smoke is detected. The fans preferably draw air in through shafts which extend the full height of the building. These shafts may be constructed from a number of prefabricated units, each of which has a fan mounted thereon.

Description

United States Patent [191 Moss [ Dec. 16, 1975 FIRE SAFETY SYSTEMS [76] Inventor: Cyril H. Moss, Heath Common,

Storrington, Sussex England [22] Filed: June 27, 1974 [2]] App]. No.: 483,818

[30] Foreign Application Priority Data Primary ExaminerWilliam E. Wayner Attorney, Agent, or Firm-Irving M. Weiner [57] ABSTRACT This invention relates to systems for clearing smoke from buildings when a fire occurs therein. Smoke detectors are provided in communal units in the building and means are provided to admit air under pressure to the communal units when smoke is detected. At the same time self-closing fire-stop doors are closed to restrict passage of smoke between the communal units. When air conditioning is provided in the building by fans which admit and extract air the extraction fans are controlled by the smoke detectors so that they are reversed when smoke is detected. The speed of operation of all fans may also be increased when smoke is detected. The fans preferably draw air in through shafts which extend the full height of the building. These shafts may be constructed from a number of prefabricated units, each of which has a fan mounted thereon.

10 Claims, 5 Drawing Figures U.S. Patent Dec. 16, 1975 Sheet2of2 3,926,101

FIRE SAFETY SYSTEMS This invention relates to fire safety systems and is particularly concerned with systems for clearing smoke from buildings when a fire occurs therein.

When a fire occurs in a large building, such as a block of flats, smoke may collect in the communal parts of the building, making it difficult for the occupants to find their way to the exits from the building. Experiments have, therefore, been carried out to assess the effectiveness of increasing the pressure in said communal parts above atmospheric pressure with the object of preventing smoke penetrating to those parts from any part of the building where a tire occurs. Although such systems have been found to be effective, they have normally been based either on the idea of introducing air under pressure to all the communal parts of the building with the result that relatively large amounts of air have been required to produce the required pressure difference, or on the idea of introducing air under pressure to a single communal part, or series of linked communal parts such as an emergency staircase, with the result that smoke has not been prevented from penetrating to other communal parts of the building.

It is an object of the present invention to provide an improvement on these two basic systems.

Accordingly, from one aspect of the present invention consists in a fire safety system for use in a building having a plurality of accommodation units and a plurality of communal units providing means of access to said accommodation units, said system including a plurality of smoke detectors in said communal units and means controlled by said smoke detectors and responsive to detection of smoke in one of said communal units to admit air under pressure to that communal unit and to restrict passage of smoke from that communal unit to another communal unit or other communal units.

It will be understood that a system in accordance with the preceding paragraph is particularly useful in a building in which the communal units are not bounded by any exterior walls of the building. In most cases, the pressurised air in the communal unit is allowed to leak out of the building purely through the cracks that are present around the doors leading into the accommodation units and around the windows in the exterior walls of the accommodation units.

If the building is provided with sealed windows so that there is insufficient leakage of air through the cracks referred to in the preceding paragraph, it is preferred that the accommodation units should be provided with uni-directional ventilators which will allow air and smoke to leave the accommodation units to the exterior of the building but will not allow air to enter the accommodation units from the exterior.

In buildings of the kind referred to in which the communal units are not bounded by any exterior walls of the building, it is necessary to provide some means of ventilating such communal units under normal conditions. In accordance with a second aspect of the invention, the means for admitting air under pressure to any communal unit in which smoke is detected are combined with means for ventilating the units in the absence of smoke.

Accordingly, from this second aspect the invention consists in a fire safety system for use in a building having a plurality of accommodation units and a plurality of communal units providing means of access to said accommodation units, said system including a plurality of smoke detectors in said communal units, means for admitting air under pressure to at least some of said communal units and means for extracting air from said units or from other communal units in communication with said units, wherein said extracting means are controlled by said smoke detectors in such a way that, if smoke is detected in one of said units, the operation of the respective extracting means is reversed so that it is effective to supply air under pressure to said one of said units.

Preferably, the rate of operation of the extracting means is increased when they are reversed, so that the supply of air under pressure is greater than the normal ventilating flow. Further, the means for admitting air under pressure under normal conditions are preferably also controlled by said smoke detectors so that, if smoke is detected in one of the units to which they supply air, the rate of operation of the admitting means is increased so that once again the air supply is greater than the normal ventilating supply.

Preferably, a system in accordance with this second aspect of the invention is utilised in combination with a system in accordance with the first aspect of the invention so that, when smoke is detected, the individual communal units are isolated from one another. In this way, it is only necessary for the supply of air to be sufficiently great that it equals the leakage through the cracks referred to above when the communal unit is at the desired pressure. This pressure should be at least 0.1 inch water gauge above atmospheric pressure and is preferably of the order of 0.25 inch of water gauge.

In a multi-stor ey building, the means for admitting air under pressure to the communal units preferably includes one or more vertical shafts having vents opening on each floor. Conveniently, such shafts can be used not only for providing air under pressure when smoke is detected but can also be used under normal conditions for ventilating the enclosed communal units.

Thus, from a third aspect the invention consists in a fire safety system for a multi-storey building, including at least one air shaft provided with vents opening on to respective floors of said building and with a fan associated with each vent and at least one smoke detector on each floor, wherein said fans are so controlled by said smoke detectors that, in the absence of smoke, all the fans operate to draw air into the shaft from their respective floors and that, in response to detection of smoke on any floor, the fan associated with the vent opening on that floor is reversed so that it expels air from said shaft on to said floor.

In a system in accordance with said third aspect of the invention it is to be understood that the fans associated with the vents on all floors except the floor on which smoke has been detected, continue to draw air into the shaft from their respective floors. Thus, these fans assist in supplying air to the fan on the floor where smoke has been detected. Consequently, the cross-sectional area of the shaft can be less than it would have to be to produce a predetermined pressure if the air had to be drawn along the full length of the shaft, either from the top or the bottom thereof. In one particular arrangement, the shaft can be closed at the bottom and open at the top.

It is to be understood that ventilating air will be supplied to each floor, preferably from a separate shaft provided with vents on each floor and fans associated with said vents, all operating to expel air from the shaft on to their respective floors. Preferably, these fans are also controlled by the smoke detectors so that their speed of operation is increased when smoke is detected on the respective floor. To enable sufficient air to be drawn into the shaft to supply not only the floor on which smoke is detected but also to continue to supplynormal ventilating air to all the other floors, it is preferred that this shaft should be open at the bottom as well as the top.

Once again, it is preferred that a system in accordance with said third aspect of the invention should be used in conjunction with a system in accordance with the first aspect of the invention so that the individual communal units are isolated from one another when smoke is detected in one of them. Such an arrangement makes it possible for the desired pressure to be maintained with fans operating to move air at rates as low as 800 cubic feet per minute.

It will be understood that the construction of the shaft, or each of the shafts, is the same for each floor of a multi-storey building. Consequently, it is convenient for the shaft, or each of the shafts, to be produced as a series of prefabricated units.

Consequently, from yet another aspect the invention consists in a prefabricated unit comprising walls surrounding a longitudinally extending space open at each end, wherein the terminal portions of said walls at one end are adapted to engage the terminal portions of the walls at the opposite end of a similar unit, wherein one of said walls is provided with an opening, the plane of which is substantially parallel to the longitudinal axis of said space and perpendicular to the planes containing the peripheries of said terminal portions, and wherein a fan is mounted in, or adjacent to, said opening.

Preferably the walls of said prefabricated unit consist of concrete, but they may alternatively consist of metal, for example, steel. When the walls consist of concrete, the upper end of each wall is preferably formed with a groove and thelower end of each wall is formed with a ridge adapted to fit in said groove. When the units are assembled, the groove is filled with sealing compound and the upper unit is lowered into place with the ridge lying in the groove and a seal being formed by the sealing compound. When the units are to be used for the construction of the central shaft, each fan is arranged to operate in one direction only but at two different speeds. On the other hand, when the units are to be used for the construction of the shafts opening into the corridors, each fan is arranged to draw air into the shaft at a relatively low speed and to expel air from the shaft at a relatively high speed.

In order to limit the obstructing effect of the fans, it is preferred that they should be mounted with at least the majority of the driving means located outside the shaft. The driving means will normally be in the form of an electric motor which may be concealed for example by means of a grille located outside the shaft.

One method of performing the invention will now be described with reference to the accompanying diagrammatic drawings, in which:

FIGS. 1 and 2 are plan views of one floor of a multistorey building provided with a fire safety system in accordance with the invention, respectively indicating the conditions before and after smoke as been detected,

FIG. 3 is a sectional elevation of part of the building taken on the line 33 of FIG. 1 looking in the direction of the arrows,

FIG. 4 is a perspective view of the communal parts of the building lookingin the direction of the arrow 4 shown in FIG. 2, and

FIG. 5 is a perspective view of a prefabricated length of shaft for use in a system in accordance with the invention.

In the particular embodiment illustrated three vertical shafts l, 2 and 3 are provided in the building, each shaft having vents opening on to all floors of the buildmg.

The building has a central lift shaft 4 and a staircase 5 with a lobby 6 located between the lift shaft and the staircase on each floor. On each floor there are also two passages 37 and 38 linking the central lobby 6 with a plurality of

accommodation units

7, 8, 9, 10, 11, 12, 13 and 14. As shown the two passages 7 and 8 are in line and extend in opposite directions from the central lobby 6. Self-closing fire-

stop doors

15, 16, 17 and 18 controlled by

smoke detectors

19, 20 and 21 are provided between the central lobby and the two passages on each floor. Thus in this particular arrangement there are three communal units on each floor, viz., the two passages 37 and 38 and the central lobby 6, and each of these communal units is capable of being isolated from the others by the self-closing doors controlled by the smoke detectors.

On each floor the shaft 1 is provided with a vent opening into the passage 37, the shaft 2 is provided with a vent opening into the central lobby 6, and the shaft 3 is provided with a vent opening into the passage 38. Each of the vents is provided with a fan as shown at 22, 23 and 24. The fans are controlled by and connected to the smoke detectors by conductors 40 (FIG. 4). The fans are mounted in their respective vents in such a way that they cause the minimum obstruction in the shaft. Each of the fans is driven by an electric motor and the fans are shown mounted with the electric motors outside the shafts. In a practical case the shafts would normally be spaced a short distance behind the walls of the passages and central lobby, so that in each case the electric motor could be concealed by means of a grille in the respective wall.

The shaft 2 is open to atmosphere at the top and at the bottom and each of the fans 23 is arranged to draw air from the shaft 2 and expel it into the respective central lobby. Each of the fans in the shafts l and 3, on the other hand, is arranged under normal circumstances to draw air into the respective shaft. The fans 23 are arranged so that they can be operated at two different speeds and the

fans

22 and 24 are arranged so that they can be reversed. Preferably the arrangement of the

fans

22 and 24 is such that they operate at a higher speed in reverse than when they are operating under normal conditions to draw air into the respective shafts.

The self-closing fire doors 15 to 18 are normally held open as shown in FIG. 1 by electro-magnetically controlled

locks

25, 26, 27 and 28. These electro-magnetically controlled locks are controlled by and connected via conductors 39 (FIG. 4) to the smoke detectors so that they are released to allow the doors to close as soon as smoke is detected. Thus, under normal conditions, ventilation of the communal units on each floor is provided by air entering the central lobby 6 from the shaft 2 and travelling in opposite directions along the passages 37 and 38 to the-shafts l and 3. When smoke is detected, however, the fire-stop doors 15 to 18 are closed as shown in FIG. 2 and the

fans

22 and 24 are reversed and operate at increased speed to supply air under pressure to the passages 37 and 38 respectively, while the fan 23 continues to operate in the same direction but at a higher speed.

In one particular arrangement the

fans

22 and 24 normally operate to move 150 cubic feet of air per minute, while the fan 23 provides 300 cubic feet of air per minute. When smoke is detected, the

fans

22 and 24 each operate to supply 600 cubic feet of air per minute while the speed of operation of the fan 23 is increased so that it also supplies 600 cubic feet of air per minute.

FIG. 5 of the drawings illustrates a prefabricated unit which may be used in the construction of the

shafts

1, 2 and 3. The unit as shown consists of concrete and is of rectangular cross-section. One end of the unit is provided with a peripheral recess 30 designed to fit a flange 31 provided on the other end of the adjacent unit. When two units are assembled together, the recess 30 of the lower unit is filled with sealing compound and the upper unit is lowered into place with the flange 31 accommodated in the recess so that an airtight seal is formed by the sealing compound One of the wider faces 32 of the unit is provided in the vicinity of the lower end thereof with an opening 33 defined by a frame 34. A plate 35 is removably fitted to the frame 34 and is designed to support a fan and electric motor unit 36. Control gear for the electric motor may also be mounted on the plate 35, or the control gear for a number of motors may be grouped at a central position on each floor, if so desired.

If it is assumed that a fire starts in the accommodation unit 10, smoke will penetrate into the passage 38 and be detected by the smoke detector 21. As soon as smoke is detected, the direction of operation of the fan 24 will be reversed so that it supplies air from the shaft 3 to the passage 38. When the fan is reversed, its speed of operation will be increased so that it supplies about 600 cubic feet of air per minute to the passage. It is to be understood that the other fans in the shaft 3 will continue to draw air into the shaft from the corresponding passages on other floors of the building, and accordingly there will be an ample supply of air available to pressurise the passage 38. At the same time as the fan 24 is reversed, the fire-stop doors to 18 will be closed by the release of the electro-magnets 25 to 28. Further, the direction of operation of the fan 22 will be reversed and its speed will be increased, while the speed of operation of the fan 23 is also increased. As a result, the spread of smoke from the passage 38 to the lobby 6 in the passage will be restricted and the staircase will be maintained as a safe area so that the occupants of the floor can leave the building by entering the staircase through the lobby 6.

At least some of the air introduced into the passage 38 will escape by leakage around the doors into the accommodation units 9, l0, l3 and 14. This will increase the air pressure in each of these accommodation units and, as a result, air will normally escape to atmosphere through cracks around the windows in the exterior walls of these accommodation units. As already mentioned, however, if the building is provided with sealed windows 41, uni-directional vents 42 must be provided in the outside walls to enable an air flow to be established from the shaft 3 through the passage 38 and the accommodation units to atmosphere.

What is claimed is:

l. A fire safety system for use in a building having a plurality of accommodation units and a plurality of communal units providing means of access to said accommodation units, said system including a plurality of smoke detectors in said communal units and means controlled by said smoke detectors and responsive to detection of smoke in one of said communal units to admit air under pressure to that communal unit and to restrict passage of smoke from that communal unit to another communal unit or other communal units.

2. A system as claimed in claim 1, wherein the pressurised air in any communal unit is allowed to leak out of the building purely through cracks that are present around the doors leading into the accommodation units and around the windows in the exterior walls of the accommodation units.

3. A system as claimed in claim 1, in which the building is provided with sealed windows and in which unidirectional ventilators are provided in the accommodation units to allow air and smoke to leave the accommodation units.

4. A system as claimed in claim 1, wherein the building includes a plurality of vertical shafts, each having vents opening on each floor of the building.

5. A system as claimed in claim 1, wherein the means for restricting transmission of smoke from the units in which smoke has been detected to other units are constituted by self-closing fire-stop doors.

6. A system as claimed in claim 5, wherein said doors are maintained open under normal conditions by electro-magnetically controlled locks, which are released to allow the doors to close when smoke is detected.

7. A fire safety system for use in a building having a plurality of accommodation units and a plurality of communal units providing means of access to said accommodation units, said system including a plurality of smoke detectors in said communal units, means for admitting air under pressure to at least some of said communal units and means for extracting air from said units or from other communal units in communication with said units, wherein said extracting means are controlled by said smoke detectors in such a way that, if smoke is detected in one of said units, the operation of the respective extracting means is reversed so that it is effective to supply air under pressure to said one of said units.

8. A system as claimed in claim 7, wherein the rate of operation of said extracting means is increased when they are reversed.

9. A system as claimed in claim 7, wherein the admitting means are controlled by smoke detectors, so that, if smoke is detected in one of the units to which they supply air, the rate of operation of the admitting means is increased.

10. A fire safety system for a multi-storey building, including at least one air shaft provided with vents opening on to respective floors of said building and with a fan associated with each vent and at least one smoke detector on each floor, wherein said fans are so controlled by said smoke detectors that, in the absence of smoke, all the fans operate to draw air into the shaft from their respective floors and that, in response to detection of smoke on any floor, the fan associated with the vent opening on that floor is reversed so that it expels air from said shaft on to said floor.

Claims

1. A fire safety system for use in a building having a plurality of accommodation units and a plurality of communal units providing means of access to said accommodation units, said system including a plurality of smoke detectors in said communal units and means controlled by said smoke detectors and responsive to detection of smoke in one of said communal units to admit air under pressure to that communal unit and to restrict passage of smoke from that communal unit to another communal unit or other communal units.

3. A system as claimed in claim 1, in which the building is provided with sealed windows and in which uni-directional ventilators are provided in the accommodation units to allow air and smoke to leave the accommodation units.