WO1986004708A1

WO1986004708A1 - Fire alarm system for living-rooms

Info

Publication number: WO1986004708A1
Application number: PCT/NO1986/000013
Authority: WO
Inventors: Mats Eriksson
Original assignee: A/S Norsk Viftefabrikk
Priority date: 1985-02-08
Filing date: 1986-02-07
Publication date: 1986-08-14
Also published as: EP0211885A1; NO158391C; NO850482L; NO158391B; AU5394786A

Abstract

Fire warming system for living-rooms, comprising use of ionic smoke detectors. The ionic smoke detector (6) is used in living-rooms ventilated by means of diffuse air supply.

Description

Fire alarm system for living-rooπis

In living-rooms most fires will start as so called smouldering fires, i.e. initially the fire will not have open flame but lead to strong development of smoke before the fire possibly changes into what may be termed a flame fire.

It is clear that in the case of fires in living-rooms, in particular in rooms with persons lying in their beds, it is of the utmost importance that warning of the fire will take place as early as at all possible so that persons staying in the living-room and who are themselves not aware that fire has broken out or who are not able to themselves escape from the living-room may receive early help in order to avoid smoke poisening. For warning-of fires heat detectors were previously most frequently used whereas the currently most frequently used fire warning means in living-rooms are so called smoke detectors.

The heat detectors are, which is implicit in this term, dependent thereon that -they have to be^' subjected to a certain minimum heat influence in order to release a signal, and when in a living-room a fire has been able to develop so far that heat detectors will give a warning signal, it will as a rule be too late to save the life of persons who are still within the living-room wherein the fire has developed. In contrast thereto, smoke detectors may be activated so early by a starting fire that persons may be rescued. As implicit in this term, the alarm from such detectors will bereleased when the detectors are subjected to a certain minimum smoke influence, and this means that warning of the fire may take place when the fire is still in the smouldering stage.

The smoke detectors currently used are of the optical type or of the ionic type. The optical smoke detectors will be more rapidly activated by a smouldering fire whereas the ionic smoke detectors will be activated at a markedly later stage and perhaps firstly when the smouldering fire has changed into a fire with open flame. Accordingly, due to early warning of a smouldering fire the so called optical smoke detectors ought to be able to be used with the greatest advantage, however, these smoke detectors will often be so sensitive that they may easily cause false warning like e.g. when the living-room has a high concentration of tobacco smoke. The ionic smoke detectors are the ones which have been most thoroughly tested and are most secure in operation and lead to least false warning, however, as mentioned they will be activated at a later stage than the optical smoke warners under otherwise equal conditions. Experiments have shown that under like conditions in living-rooms wherein smouldering fire has been intentionally initiated it will take about 3 times longer to activate an ionic smoke detector than to activate an optical smoke detector.

It is an object of the invention to provide a fire warning system using ionic smoke detectors and with obtainment of a substantially reduced period of time between commensing smouldering fire and the time at which the ionic smoke detector will be activated and give a warning signal.

Disclosure of the invention

There is provided by the invention a fire warning system which comprises use of an ionic smoke detector,the system being characterized therein that the ionic smoke detector is used in living-rooms which are ventilated by means of diffuse air supply.

Detailed disclosure of the invention and the drawing

The main principle by conventional ventilation of living-rooms is the so called mixing ventilation, i.e. with the same temperature and air quality being created in the entire room. This means that contaminations, like tobacco smoke, heat or odour etc., are mixed and uniformally distributed throughout the room. The so called diffuse ventilation is based on another principle. By diffuse ventilation the ventilation air is introduced at floor level, and the used air in the room will be discplaced by the ventilation air introduced and be sucked out at ceiling level Diffuse air supply is based thereon that fresh air is supplied at low level in the occupation zone at very low velocity and with uniform distribution of the introduced air. This is introduced with a slightly lower temperature than the room air and utilizes the law of nature that warm air is ascending. Accordingly, the contaminations in the room ventilated by diffuse air supply will be brought up to the ceiling and be withdrawn at ceiling level without the contaminations being stirred around in the living-room.

Primarily, in all cases of fire early detection of the fire is desired, and the present invention is based on the recognition that by the combination of diffuse air supply for ventilation of living-rooms and ionic smoke detector the latter may be influenced earlier by a higher and alarm-releasing smoke concentration in cases of fire than when using no ventilation or normal mixing ventilation of living-rooms, because the diffuse air supply, as mentione will cause the contaminations, i.e. in this case the smoke, in the living-room to be brought up to the ceiling and. there influence the ionic^' smoke detector and put it into.action.

In this connection experiments with smouldering fire have been carried out in living-rooms in order to determine how the time of alarm would be influenced when using optical and ionic smoke detectors respectively with ventilation of the room in agreement with the diffusion principle and in agreement with the traditional mixing ventilation. The experiments clearly showed that the difference between the time of alarm with optical and ionic smoke detectors respectively was strongly reduced when using ventilation in agreement with-the diffusion principle. It was found that t difference between the time of alarm with the two types of smoke detectors was reduced such that the ionic smoke detect was caused to be released after a period of time which was only about 20% longer than the time which passed before the optical smoke detector was caused to be released. By traditional ventilation it was necessary with an approximate 300% longer time before the ionic smoke detector was caused to be released compared with the time which passed before th optical smoke detector was caused to be relased under other¬ wise equal conditions. It was simultaneously found that the time of alarm for the optical smoke detector was only marginally displaced towards a- somewhat shorter time before the optical smoke detector was caHsed to be released when using diffuse air supply.

Besides the clear advantage that when using a smoke warning system according to the invention there is obtained a more rapid time of alarm upon development of smoke in a room as a consequence of smouldering fire when using ionic smoke detectors, which are more safe in operation and give less false alarm than optical smoke detectors, the additional advantage is obtained by the system according to the invention that because the contaminations rapidly are brought up towards the ceiling when using diffuse air supply the risk that persons staying in the room will be poisoned by smoke will be strongly reduced, and concurrently the free sight will be better maintained in the room with smouldering fire and make it easier for people to find and rescue persons . staying in the room. . .

By means of. the possibility provided by the present invention of being able to use ionic smoke detectors in connection with ventilation with diffuse air supply to the room, whereby an early release of the signal from the ionic smoke detector in case of smouldering fire will be obtained thereby that the smoke rapidly will be displaced up towards the ceiling level of the room and there influence the ionic smoke detector, it has also been made possible rapidly and reliably to control the ventilation air supplied to the room in case of a smouldering fire therein, by letting the electric signal from the detector activate a regulator for the amount of air supplied, a so called VAV unit ("variable air volume") . The ionic smoke detector may then be arranged in the ceiling or in the channel at ceiling level for carrying off the used room air, and due to the high concentration of smoke which is rapidly^' obtained at ceiling level when using diffuse air supply to the room in which the smouldering fire occurs, the rapidlyreleased signal from the smoke detector can be used for controlling the supply of air to the room in order to increase the height of the stratum in the room, i.e. the height of the stratum wherein the concentration of smoke is relatively low. The strength of the signal from the ionic smoke detector is dependent upon the concentration of the smoke, and it is thereby possible to obtain an automatic control of the amount of ventilation air supplied in dependence of the concentration of the smoke detected by the ionic smoke detector. Automatic control of the supply of ventilation air in dependence of the actual demand for ventilation air is known per se, and a such control has normally been controlled by a signal from a room thermostate or a carbon dioxide measuring device for reasons of comfort or energy economics. However, it has hitherto not been suggested to let the signal froma smoke detector,

^"let alone from an ionic smoke detector, influence a such integrated apparatus for the control of the amount of air. In principle, a such circuit for the control of the amount of air consists of a control flap in the ventilation air channel from which ventilation .air is supplied into the ventilation air distributing means in the room, a control motor, an air stream regulator and an air stream measuring device. The air stream regulator will continuouslymeasure the air stream in the ventilation air channel in relation to the amount of ventilation air indicated by the strength of the signal from the ionic smoke detector, and if these air stream values are different from one another the regulator will by means of the control motor automatically influence the position of the flap in the ventilation air channel so that the stream of ventilation air will be proportioned to the strength of the signal given off by the ionic smoke detector. A suitable apparatus for fulfilling this function is the apparatus which is sold under the trade name "OPTIVENT^ VAV Ter inalapparat" and delivered by Flakt AB, Sweden. A sketch showing the principles of a such solution is shown in the drawing.

The drawing shows a section of a ventilation air channel 1 through which ventilation air flows in the direction of the arrow. In the ventilation air channel a controllable flap 2 is arranged, and the position of the flap is influenced by a flap control motor 3 which receives a command signal from an air stream regulator 4 which continuously measures the stream of ventilation air at 5 in the ventilation air channel 1. The air stream regulator 4 is electrically connected to an ionic smoke detector 6 which gives signals to the air stream regulator, the strength of the signal being dependent upon the concentration of the smoke^* detected at the place the smoke detector is positioned. The air stream regulator 4 is supplied with pneumatic or electric power from a corresponding source 7, and if the air stream measured by the air .stream regulator 4 does not correspond to the air stream dictated by the electrical signal from the ionic smoke detector 6 the air stream regulator 4 will through the flap control motor 3 automatically change the position of the flap 2 in the ventilation air channel 1 so that the amount of ventilation air into the ventilated room at floor level will increase proportionally with the strength of the signal from the ionic smoke detector 6.

•The advantages of a such system are obvious. Instead of, as previously known, to let the stream of ventilation air be controlled by signals from a room thermostate which only to a small degree, if at all, will be able to detect a temperature increase in the ventilated room in which a smouldering fire occurs but which probably firstly will react when the smouldering fire has changed into a fire with open flames, whereby it often will be too late to save the life of persons staying in the room and who may not by themselves escape from the room, the ionic smoke detector will at a certain minimum concentration of the smoke at the place where the ionic smoke detector is positioned react spontaneously thereto and give off a signal to the air stream regulator 4 which will then automatically through the flap control motor 3 control the position of the flap 2 in the ventilation air channel 1 so that an increased amount of ventilation air will be introduced into the room wherein the smouldering fire occurs and causing .an increased stream of ventilation air into the room in order to displace the developed smoke up towards, ceiling level. It may thereby be ensured that a stratum of relatively low concentration of smoke all the time will be created in the room up to a height which essentially corresponds to the head level of persons staying in the room. The persons staying in the room will thereby most probably avoid being poisoned by the smoke, and rescue personnel will have sufficient free sight when . entering the room to find the persons in the room and help them out of the room.

The electrical signal from the ionic smoke detector may also be utilized for continuously controlling the amount of ventilation air and release an alarm firstly at a pre¬ determined concentration of smoke. Thus, prior to the release of the alarm the system will all the time be functioning and improve the air conditions in the room by controlling the amount of air.

When the alarm signal has been released, this may be used for more comprehensive influence from acentral ^'in order to control the pressure conditions in adjacent rooms and corridors or ways of escape in order to prevent spreading of the smoke. Such measures are known per se when fire alarms are released. The advantage of the present fire warning system in this connection is the rapid and reliable release of the alarm in direct dependence upon the concentration of smoke in the room.

In order to obtain an as rapid influence by the smoke as possible upon the ionic smoke detector it is particularly advantageous that this be positioned at the inlet to or within the air exhaust channel from the room.

Claims

C l a i m s

1. Fire alarm system for living-rooms, comprising use of ionic smoke detectors, characterized in that the ionic smoke detector (6) is used in living-rooms which are ventilated by means of diffuse air supply.

2. Fire alarm system as claimed in claim 1, characterized in that the ionic smoke detector (6) is electrically connected to an air stream regulator (4) which is capable of regulating the amount of ventilation air introduced into the room per unit time in dependence of the strength of the electrical signal which the smoke detector (6) gives off to the air stream regulator (4) .