AU2013101129A4 - Method and device for maintaining breathable air - Google Patents

Abstract

A device and method for maintaining breathable air in a refuge chamber is disclosed. The device comprises a gauge to monitor differential pressure between inside the refuge chamber and outside the refuge chamber; a detector to detect one 5 or more hazardous or harmful substance inside the refuge chamber; a compressed air storage bank to maintain the differential pressure at a desired positive differential level and to reduce the level of at least one of a respective one or more detected hazardous or harmful substance below a set level by varying an amount of stored compressed air released into the refuge chamber. PPU CONTROL PANEL C -] POLYWhON cc REFUGECHAMBE 01r 7 1us BALL VALVyE FLOW CONTROL VALVE FLOW METER { CHECK VALVE PRSUEREGULATOR HIGH PRESSURE SILENCER ----- MEDIUM PRESSURE PRESURE AUGELOW P RESSURE SAFETY VALVE [W NEEDLE VALVE jDRAEGER SAFETY PACIFIC DIFFERENTIAL PRESSURE SWITCH * PPU 5000 AT~MOOR1AISH 22/10/12 PNEUMATIC DIAGRAM DIFFERENTIAL PRESUREGAUGE PPU-3502409-PD A2 SILECER EDIU PRES *"

Description

P/00/01I Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A DIVISIONAL INNOVATION PATENT ORIGINAL Name of Applicant: DRAEGER SAFETY PACIFIC PTY LTD Actual Inventors: Amir MODIRZAREH Maximilian Stefan Theodor REILING Mitchell Francis SMITH Address for Service: Houlihan 2 , Level 1, 70 Doncaster Road, Balwyn North, Victoria 3104, Australia Invention Title: METHOD AND DEVICE FOR MAINTAINING BREATHABLE AIR The following statement is a full description of this invention, including the best method of performing it known to the Applicant:- 2 TITLE METHOD AND DEVICE FOR MAINTAINING BREATHABLE AIR The present application is a divisional application from Australian patent 5 application number 2012244195. The entire disclosures of Australian patent application number 2012244195 is incorporated herein by reference. FIELD THIS INVENTION described herein relates generally to a method and device for maintaining breathable air for example, in a refuge chamber. In 10 particular, the invention is directed to a method and device for maintaining breathable air for example, in a refuge chamber, in which a positive pressure is maintained, although the scope of the invention is not necessarily limited thereto. BACKGROUND There are numerous hazardous environments in which refuge chambers or 15 safe rooms or other similar refuges are installed for people to seek shelter in emergencies. For example, these facilities are found in underground mining, oil and gas plants, petro-chemical plants and submarines. Current refuge chambers use mine or external air as a source of breathable air and may be equipped with compressed oxygen cylinders and a scrubbing 20 system. The scrubbing system removes carbon dioxide (C0 2 ) and a manual dosing system adds oxygen to the refuge chamber to sustain life until the emergency has passed or rescue can be performed. In order to sustain life for the longest period possible, to have the highest probability that rescue can be performed or the emergency passes, improved 25 means of maintaining breathability of the air in the refuge chamber are desirable. SUMMARY The present invention is broadly directed to a method and device for maintaining breathable air for example, in a refuge chamber, safe room, change over station or other confined space. In particular, the invention is directed to a 30 method and device for maintaining breathable air by providing a positive pressure. In one embodiment the positive pressure is maintained in an efficient manner.

3 In another preferred embodiment a method and device for avoiding deleterious effects of a hazardous substance is provided. In yet another preferred embodiment a method for testing leakage and determining leakage rate in a refuge chamber is provided. 5 In one aspect, there is provided a device for maintaining breathable air in a refuge chamber, the device comprising: a gauge to monitor differential pressure between inside the refuge chamber and outside the refuge chamber; a compressed air storage bank to maintain the differential pressure at a 10 desired positive differential level by varying an amount of stored compressed air that is released into the refuge chamber. In one embodiment of the first aspect the device further comprises a valve that may be operated to control release of stored compressed air. The valve may comprise a manual flow valve or an automatic flow valve. 15 In another embodiment of the first aspect the desired positive differential level comprises a safe level for the refuge chamber external conditions. The safe level may be a differential pressure of between 100 Pa and 1000 Pa. In one embodiment the safe level may be 200 Pa. The device of the first aspect may further comprise a source of oxygen for 20 inhalation by one or more occupants of the refuge chamber. The device of the first aspect may further comprise a carbon dioxide scrubber for removing carbon dioxide, including carbon dioxide exhaled by the one or more occupants of the refuge chamber. In one embodiment the device of the first aspect further comprises a 25 processor to receive the differential pressure monitored by the gauge as an input and to send an output to the valve to vary the amount of stored compressed air released. The processor may be comprised in a computer or a programmable logic controller. 30 In one embodiment of the first aspect the device is a pneumatic device. In a second aspect there is provided a method for maintaining breathable air in a refuge chamber, the method comprising: 4 monitoring differential pressure between inside the refuge chamber and outside the refuge chamber; in response to the monitored differential pressure varying the amount of stored compressed air released into the refuge chamber to provide a desired 5 positive differential level and thereby maintain breathable air in the refuge chamber. In one embodiment of the second aspect the method further comprises operating a valve to control release of the stored compressed air. The valve may comprise a manual flow valve or an automatic flow valve. 10 In another embodiment of the second aspect the desired level comprises a safe level for the refuge chamber external conditions. The safe level may comprise a differential pressure of between 100 Pa and 1000 Pa. In one embodiment the safe level is a differential pressure of 200 Pa. The method of the second aspect may further comprise providing a source 15 of oxygen for inhalation by one or more occupants of the refuge chamber. The device of the second aspect may further comprise removing carbon dioxide, including carbon dioxide exhaled by the one or more occupants, from the refuge chamber. In one embodiment the second aspect further comprises receiving in a 20 processor the differential pressure monitored by the gauge as an input and sending an output to the valve to vary the amount of stored compressed air released. The processor may be comprised in a computer or a programmable logic controller. In one embodiment of the second aspect the method is a pneumatic 25 method. In a third aspect the invention provides a device for maintaining breathable air in a refuge chamber, the device comprising: a gauge to monitor differential pressure between inside the refuge chamber and outside the refuge chamber; 30 a detector to detect one or more hazardous or harmful substance inside the refuge chamber; 5 a compressed air storage bank to maintain the differential pressure at a desired positive differential level and to reduce the level of at least one of a respective one or more detected hazardous or harmful substance below a set level by varying an amount of stored compressed air released into the refuge chamber. 5 In one embodiment of the third aspect the device further comprises a valve that may be operated to vary the amount of stored compressed airs released. The valve may comprise a manual flow valve or an automatic flow valve. In another embodiment of the third aspect the detector comprises an electronic detector, for example a Polytron 8000. 10 In another embodiment of the third aspect the one or more harmful or hazardous substance comprises carbon monoxide and the set level is less than 50 ppm; 45 ppm; 40 ppm; 35 ppm; 30 ppm; 25 ppm; 20 ppm; 15 ppm; 10 ppm; 5 ppm; 4 ppm; 3 ppm; 2 ppm or 1 ppm. In another embodiment the one or more harmful or hazardous substance 15 comprises: one or more of one or more acidic compound, COCl 2 , H 2 , H202, H 2 S, HCl, HCN, PH 3 /AsH 3 , Hydride, N 2

H

4 , NH 3 , NO, NO 2 , 02, Ozone, OV1, OV2 and/or

SO

2 . In one embodiment of the third aspect the device further comprises one or more sensor for a respective one or more hazardous or harmful substance each of 20 the one or more sensor providing an input to the detector such that the detector provides an output comprising a concentration of each of the respective one or more hazardous or harmful substances. In another embodiment of the third aspect the desired positive differential level is a safe level for the refuge chamber external conditions. 25 The safe level may be a differential pressure of between 100 Pa and 1000 Pa. In one embodiment the safe level may be 200 Pa. The device of the third aspect may further comprise a source of oxygen for inhalation by one or more occupants of the refuge chamber. The device of the third aspect may further comprise a carbon dioxide 30 scrubber for removing carbon dioxide, including carbon dioxide exhaled by the one or more occupants of the refuge chamber.

6 In one embodiment the device of the third aspect further comprises a processor to receive the differential pressure monitored by the gauge and a result of the detection by the detector as an input and to send an output to the automatic valve to vary the amount of stored compressed air released. 5 The processor may be comprised in a computer or a programmable logic controller. In one embodiment of the third aspect the device is a pneumatic device. In a fourth aspect there is provided a method for maintaining breathable air in a refuge chamber, the method comprising: 10 monitoring differential pressure between inside the refuge chamber and outside the refuge chamber; detecting an amount of one or more hazardous or harmful substance inside the refuge chamber; varying an amount of stored compressed air released into the refuge 15 chamber to maintain the differential pressure at a desired positive differential pressure and to reduce the amount of a respective one or more detected hazardous or harmful substances below a set level to thereby maintain breathable air in a refuge chamber. In one embodiment of the fourth aspect the method further comprises 20 operating a valve to control release of the stored compressed air. The valve may comprise a manual flow valve or an automatic flow valve. In another embodiment of the fourth aspect the detector may comprise an electronic detector, for example a Polytron 8000. In another embodiment of the fourth aspect the one or more harmful or 25 hazardous substance comprises carbon monoxide and the set level is less than 50 ppm; 45 ppm; 40 ppm; 35 ppm; 30 ppm; 25 ppm; 20 ppm; 15 ppm; 10 ppm; 5 ppm; 4 ppm; 3 ppm; 2 ppm or 1 ppm. In yet another embodiment the one or more harmful or hazardous substance comprises one or more of one or more acidic compound, COCl2, H2, 30 H202, H2S, HCl, HCN, PH3/AsH3, Hydride, N2H4, NH3, NO, N02, 02, Ozone, OV1, OV2 and/or SO 2

.

7 In one embodiment of the fourth aspect the method further comprises sensing one or more hazardous or harmful substance in a respective one or more sensor and providing an input to the detector such that the detector provides an output comprising a concentration of each of the one or more hazardous or 5 harmful substance. In another embodiment of the fourth aspect the desired level comprises a safe level for the refuge chamber external conditions. The safe level may comprise a positive differential pressure of between 100 Pa and 1000 Pa. In one embodiment the safe level may be a positive 10 differential pressure of 200 Pa. The method of the fourth aspect may further comprise providing a source of oxygen for inhalation by one or more occupants of the refuge chamber. The method of the fourth aspect may further comprise removing carbon dioxide, including carbon dioxide exhaled by the one or more occupants, from the 15 refuge chamber. In one embodiment the fourth aspect further comprises receiving in a processor the differential pressure monitored by the gauge and a result of the detecting as an input and sending an output to the automatic valve to vary the amount of stored compressed air released. 20 The processor may be comprised in a computer or a programmable logic controller. In one embodiment of the fourth aspect the method is a pneumatic method. In a fifth aspect the invention provides a device for determining a leakage 25 rate in a refuge chamber, the device comprising: air stored in one or more cylinders to supply air into the refuge chamber sufficient to maintain a desired differential pressure between the inside of the refuge chamber and the outside of the refuge chamber; a flow meter to determine the rate of flow of the compressed air into the 30 refuge chamber to determine the leakage rate of the refuge chamber. In one embodiment of the fifth aspect the device is a pneumatic device. In another embodiment of the fifth aspect the device comprises a computer 8 processor to receive the flow determined by the flow meter and to calculate the leakage rate and provide the calculated leakage rate as an output. In a sixth aspect there is provided a method of determining a leakage rate in a refuge chamber, the method comprising: 5 releasing an amount of compressed air stored in one or more cylinder into the refuge chamber sufficient to maintain a desired differential pressure between the inside of the refuge chamber and the outside of the refuge chamber; determining a flow rate of compressed air required to be released into the refuge chamber to maintain the desired differential pressure to thereby determine 10 the leakage rate of the refuge chamber. In one embodiment of the sixth aspect the method is a pneumatic method. In another embodiment of the sixth aspect the method comprises determining the flow rate in a computer processor. The invention also provides a method and device of any of the above 15 embodiments substantially as herein described with or without reference to the figures. US patents do not constitute common general knowledge in Australia or other countries. Any discussion of the prior art throughout the specification should in no 20 way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers 25 or steps. BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention may be readily understood and put into practical effect, reference will now be made to the accompanying illustrations, wherein like reference numerals refer to like features and wherein: 30 FIG. 1 shows a front view of one embodiment of a component of a device according to the invention; FIG. 2 shows a rear perspective view of one embodiment of a component 9 of a device according to the invention; FIG. 3 shows a pneumatic circuit diagram of one embodiment of a device according to the invention. FIGS. 4A and 4B show a schematic diagram of one embodiment of a 5 computer according to the invention. DETAILED DESCRIPTION The inventors have produced novel and inventive devices and methods for maintaining a positive pressure and breathable air in a refuge chamber and for determining a leakage rate of the refuge chamber. 10 Through diligent study the present inventors have discovered that by providing a positive pressure inside a refuge chamber contamination of the breathable air from outside may be prevented or at least reduced. Further, the present inventors have provided an efficient means of using compressed air to maintain the internal positive pressure. By monitoring the 15 differential pressure, efficient use may be made of the compressed air supply so that less compressed air has to be utilised. This brings space and economical advantages or which can be converted to a longer supply of positive pressure. The present invention is of significant advantage because it can efficiently use compressed air to keep the refuge chamber permanently pressurised to 20 prevent contamination from outside Further, as exemplified herein, the inventors have provided a novel and inventive method and device for determining a leakage rate of a refuge chamber. Hitherto, a vacuum was required to be created inside the refuge chamber in order to determine the leakage. The present invention does not require the additional 25 machinery and testing equipment required to create a vacuum and instead monitors the compressed air required to maintain a pressure differential in the refuge chamber. Although not limited thereto the invention will be described with reference to a refuge chamber. The invention may find applications for example 30 in a safe room, a change-over station or any other confined space. A refuge chamber is any sheltered area that one or more user may seek refuge in during an emergency or hazardous event. Examples of refuge chambers 10 are those placed in underground mines and used during partial collapses and/or during hazardous gas exposures. FIG. 1 shows a front view of one embodiment of an operations panel 102 of a device for maintaining breathable air 100 to a refuge chamber 120 (not 5 shown) according to the invention. Panel 102 comprises pressure gauge 1 which displays the pressure of compressed air cylinder(s) 124 (see FIG. 3). Gauge 1 is a safety pattern 63 mm diameter gauge displaying pressure between 0-400 bar. Gauge 1 is rated to 400 bar. 10 Valve 2 is a ball valve and can be used to turn device 100 on and off. Gauge 3 monitors and displays the differential pressure between the inside of refuge chamber 120 and the outside. In the embodiment shown gauge 3 is able to display a differential pressure between 0-500 Pa and has a maximum of 500 Pa. Gauge 3 shows the differential pressure inside refuge chamber and outside 15 can be read to determine if refuge chamber 120 has a positive differential pressure inside. A positive differential pressure inside refuge chamber 120 is highly desirable to prevent contamination in refuge chamber 120. Button 4 is an electrical button that can be used to turn the automatic flow control on or off. When button 4 is switched to "off' the flow rate must be 20 controlled manually using valve 8. When this button is "on" the flow control is automatically set to meet the desired positive differential pressure by valve 18. Gauge 5 is a pressure gauge. In the embodiment shown gauge 5 is a safety pattern 63 mm diameter gauge displaying pressure between 0-10 bar. Gauge 5 displays the outlet pressure of the pressure reducer 11 which is set to 6 25 bar. Sensor 6 detects one or more hazardous or harmful substances inside refuge chamber 120 and provides an output to detector 7. In the embodiment shown sensor 6 comprises a carbon monoxide (CO) detector. In other embodiments sensor 6 comprises one or more sensors or a plurality of sensors, for 30 examples, sensors for CO, carbon dioxide (CO 2 ), oxygen (02). When the sensor 6 detects CO, the set level of CO may be lower than 50 ppm. In another embodiment of the set level is less than 50 ppm; 45 ppm; 40 11 ppm; 35 ppm; 30 ppm; 25 ppm; 20 ppm; 15 ppm; 10 ppm; 5 ppm; 4 ppm; 3 ppm; 2 ppm or 1 ppm. In other embodiments sensor 6 may detect one or more acidic compound, COCl 2 , H 2 , H 2 0 2 , H 2 S, HCl, HCN, PH 3 /AsH 3 , Hydride, N 2

H

4 , NH 3 , NO, NO 2 , 02, 5 Ozone, OV 1 , OV 2 and/or SO 2 . In still other embodiments device 100 comprises a sensor for each of one or more acidic compound, COCl 2 , H 2 , H 2 0 2 , H 2 S, HCl, HCN, PH 3 /AsH 3 , Hydride, N 2

H

4 , NH 3 , NO, NO 2 , 02, Ozone, OV1, OV 2 and/or SO 2 . Detector 7 receives an input from one or more sensor 6 and determines 10 and displays data such as the concentration of, the detected gas including hazardous or harmful gases. In the embodiment shown detector 7 is a multi detector such as, a Polytron 8000 which is capable of detecting over 100 gases. The Polytron 8000 is available from Drager Safety Pacific Pty Ltd, Axxess Corporate Park, Unit 99, 45 Gilby Road, MT WAVERLY VIC 3149. 15 In the automatic embodiment, detector 7 also operates valve 18 to increase or decrease the release of compressed air into refuge chamber 120 in response to the determination of the concentration of the one or more hazardous or harmful substances. Valve 8 is a needle valve used in manual operation of the device 100. A 20 user is able to observe the flow rate of compressed air into the refuge chamber 120 on flow meter 9 and increase or decrease the rate of flow of compressed air into refuge chamber 120 by regulating the flow of the needle valve 8. A user may also change the flow of valve 8 in response to the display of detector 7. 25 Valve 10 is a ball valve (reducer bypass). If the reducer 11 fails, by closing valve 2 and opening valve 10, which is rated to high pressure, air can be released into refuge chamber 120. Dual stage pressure reducer 11 operates to reduce the pressure from 350 max to 6 bar. 30 If pressure reducer 11 is not set to 6 bar or fails, safety valve vent the air to protect the pneumatic components of device 100 from high pressure. 12 Silencers 13, 14 and 16 are noise reduction devices. When air is being 12 released it can make a loud noise. The inventors incorporation of silencers 13, 14 and 16 reduces this noise. When reducer 11 fails, if a user opens valve 10 a huge amount of flow will be released and to prevent this from happening flow control valve 15 controls the 5 flow and keeps it under a pre-set amount This flow control valve is rated to high pressure. Differential pressure switch 17 compares the differential pressure between inside refuge chamber 120 and outside. If the differential pressure is to be varied switch 17 operates solenoid valve 18 to vent or stop venting the compressed air 10 and thereby vary the pressure inside refuge chamber 120 and the differential pressure. Valve 18 is a solenoid valve (2 way, NC by spring) 18 which is normally closed by spring force and it will be open if either the differential switch 17 or detector 8 operate it. When valve 18 is open it releases compressed air into the 15 room to increase the pressure and if present push any harmful or hazardous substance out, or at least diluting it. As shown in FIG. 2, device 100 comprises a manifold 110 comprising a network of hose 112 and connectors linking the components of device 100. In the embodiment shown manifold 110 comprises stainless steel connectors and 20 flexible hose 112 which is 6X4 mm hose. The tubes comprise 3/8" and 1/4" tubes. In another embodiment manifold 110 may comprise coated mild steel, brass or polymer. Quick connect 20 and valve 21 allow connection to a compressor (not shown) and enables a user to recharge cylinders 124 while located in the chamber 25 120 by using a mobile compressor with a proper filtration system. Based on the teachings herein a skilled person is readily able to select other suitable valves, gauges, meters, sensors, detectors, cylinders and refuge chambers. FIG. 3 shows a schematic diagram of one embodiment of the device 100 30 according to the invention including manifold 110 linking the components of device 100 with refuge chamber 120 and the compressed air supply 122 which comprises cylinders 124.

13 Refuge chamber 120 may be any suitable refuge chamber and may be designed for 4 to 30 occupants and also for different durations for instance: 12, 24, 36 hours. In the embodiment shown, air supply 122 comprises 2 cylinders. In other 5 embodiments supply may comprise a plurality of cylinders arranged into one or more banks of cylinders. In response to the monitored differential pressure the amount of the amount of stored compressed air released into the refuge chamber may be varied to provide a desired positive differential pressure and thereby maintain breathable 10 air in the refuge chamber. The desired positive differential level may be a safe level for the refuge chamber 120 external conditions. A skilled person is readily able to select such a safe level upon assessment of the external conditions. In one embodiment the safe level is a differential pressure of between 100 Pa and 1000 Pa. In one particular 15 embodiment the safe level is 200 Pa. In another embodiment the desired level is lower than 200 Pa. As mentioned above the release of compressed air may also be varied in response to sensor 7 and detector 8 detecting one or more hazardous or harmful substance. By increasing the amount of compressed air the concentration of the 20 harmful or hazardous substance in refuge chamber 120 can be decreased. FIG. 3 shows high pressure, medium pressure and low pressure lines. These lines have three different pressure ratings, high pressure max 350 bar (cylinder pressure), 6 bar pressure after pressure regulator, and atmospheric pressure. 25 In one embodiment cylinders 122 comprise 50 litre, high pressure cylinders with a nominal working pressure of 350 bar. Based on the description herein a skilled person is readily able to select other suitable cylinders. Device 100 may further comprise a source of oxygen 1246for inhalation by one or more occupants of the refuge chamber. 30 Another addition to device 100 may be a carbon dioxide scrubber 125 for removing carbon dioxide, including carbon dioxide exhaled by the one or more occupants of the refuge chamber.

14 The invention also provides a device for determining a leakage rate in a refuge chamber, such as refuge chamber 120, comprising releasing air stored in cylinders 124 into refuge chamber 120 sufficient to maintain a desired differential pressure between the inside of the refuge chamber 120 and the outside of the 5 refuge chamber 120. This device also comprises a flow meter, such as flow meter 9, to determine the rate of flow of the compressed air into refuge chamber 120 when no air is consumed to determine the leakage rate of the refuge chamber. In one embodiment of measuring the leakage rate, a manual method may be used. By opening needle valve 8, air starts releasing through flow meter 9. By 10 adjusting the flow rate very slowly and then monitoring differential gauge 3. As soon as the differential pressure starts going up, we can assume the flow rate shown by flow meter 9, as the leakage rate In this embodiment of determining leakage, the desired differential pressure may be a level used to monitor the air released to maintain it as the 15 leakage rate. Prior art methods require the creation of a vacuum inside the refuge chamber in order to determine the leakage rate. The creation of the vacuum requires additional equipment and may be time consuming and difficult to obtain an accurate measure. The present method and device avoids these disadvantages. 20 The devices disclosed herein may be specially constructed for the required purposes, e.g a pneumatic controlled device 100, or may comprise a general purpose computer or other device, for example a programmable logic controller, selectively activated or reconfigured by a computer program stored in the computer or other device. 25 The methods presented herein are not inherently related to any particular computer or other apparatus. Various general purpose machines may be used with programs in accordance with the teachings herein. Alternatively, the construction of more specialized apparatus, for example a pneumatic controlled apparatus, to perform the required method steps may be appropriate. The structure of a 30 conventional general purpose computer 200 will appear from the description below with reference to FIGS. 4A and 4B. Based on this description a skilled person will readily be able to select and/or design a suitable programmable logic 15 controller. In addition, the present specification also implicitly discloses a computer program, in that it would be apparent to the person skilled in the art that the individual steps of the method described herein may be put into effect by 5 computer code. The computer program is not intended to be limited to any particular programming language and implementation thereof. It will be appreciated that a variety of programming languages and coding thereof may be used to implement the teachings of the disclosure contained herein. Moreover, the computer program is not intended to be limited to any particular control flow. 10 There are many other variants of the computer program, which can use different control flows without departing from the spirit or scope of the invention. Furthermore, one or more of the steps of the computer program may be performed in parallel rather than sequentially. Such a computer program may be stored on any computer readable medium. The computer readable medium may 15 include storage devices such as magnetic or optical disks, memory chips, or other storage devices suitable for interfacing with a general purpose computer. The computer readable medium may also include a hard-wired medium such as exemplified in the Internet system, or wireless medium such as exemplified in the GSM mobile telephone system. The computer program when loaded and executed 20 on such a general-purpose computer effectively results in an apparatus that implements the steps of the preferred method. As seen in Fig. 4A, the computer system 200 is formed by a computer module 201, input devices such as a keyboard 202, a mouse pointer device 203, a scanner 226, a camera 227, and a microphone 280, and output devices including a 25 printer 215, a display device 214 and loudspeakers 217. An external Modulator Demodulator (Modem) transceiver device 216 may be used by the computer module 201 for communicating to and from a communications network 220 via a connection 221. The network 220 may be a wide-area network (WAN), such as the Internet or a private WAN. Where the connection 221 is a telephone line, the 30 modem 216 may be a traditional "dial- up" modem. Alternatively, where the connection 221 is a high capacity (eg: cable) connection, the modem 216 may be a broadband modem. A wireless modem may also be used for wireless connection 16 to the network 220. The computer module 201 typically includes at least one processor unit 205, and a memory unit 206 for example formed from semiconductor random access memory (RAM) and semiconductor read only memory (ROM). The 5 module 201 also includes an number of input/output (1/0) interfaces including an audio-video interface 207 that couples to the video display 214, loudspeakers 217 and microphone 280, an 1/0 interface 213 for the keyboard 202, mouse 203, scanner 226, camera 227 and optionally a joystick (not illustrated), and an interface 208 for the external modem 216 and printer 215. In some 10 implementations, the modem 216 may be incorporated within the computer module 201, for example within the interface 208. The computer module 201 also has a local network interface 211 which, via a connection 223, permits coupling of the computer system 200 to a local computer network 222, known as a Local Area Network (LAN). As also illustrated, the local network 222 may also couple 15 to the wide network 220 via a connection 224, which would typically include a so-called "firewall" device or device of similar functionality. The interface 211 may be formed by an Ethernet circuit card, a Bluetooth wireless arrangement or an IEEE 802.11 wireless arrangement. The interfaces 208 and 213 may afford either or both of serial and parallel 20 connectivity, the former typically being implemented according to the Universal Serial Bus (USB) standards and having corresponding USB connectors (not illustrated). Storage devices 209 are provided and typically include a hard disk drive (HDD) 210. Other storage devices such as a floppy disk drive and a magnetic tape drive (not illustrated) may also be used. An optical disk drive 212 25 is typically provided to act as a non- volatile source of data. Portable memory devices, such optical disks (eg: CD-ROM, DVD), USB-RAM, and floppy disks for example may then be used as appropriate sources of data to the system 200. The components 205 to 213 of the computer module 201 typically communicate via an interconnected bus 204 and in a manner which results in a 30 conventional mode of operation of the computer system 200 known to those in the relevant art. Examples of computers on which the described arrangements can be practised include IBM-PC's and compatibles, Sun Sparcstations, Apple Mac; or 17 alike computer systems evolved therefrom. The methods of the invention may be implemented using the computer system 200 wherein the methods of the invention, may be implemented as one or more software application programs 233 executable within the computer system 5 200. In particular, the steps of the method 100 are effected by instructions 231 in the software that are carried out within the computer system 200. The software instructions 231 may be formed as one or more code modules, each for performing one or more particular tasks. The software may also be divided into two separate parts, in which a first part and the corresponding code modules 10 performs the method of the invention and a second part and the corresponding code modules manage a graphical user interface between the first part and the user. The software may be stored in a computer readable medium, including the storage devices described below, for example. The software is loaded into the 15 computer system 200 from the computer readable medium, and then executed by the computer system 200. A computer readable medium having such software or computer program recorded on it is a computer program product. The use of the computer program product in the computer system 200 preferably effects an advantageous apparatus for implementing the method of the invention. 20 The software 233 is typically stored in the HDD 210 or the memory 206. The software is loaded into the computer system 200 from a computer readable medium, and then executed by the computer system 200. Thus for example the software may be stored on an optically readable CD-ROM medium 225 that is read by the optical disk drive 212. A computer readable medium having such 25 software or computer program recorded on it is a computer program product. The use of the computer program product in the computer system 200 preferably effects an advantageous apparatus for implementing the method of the invention. In some instances, the application programs 233 may be supplied to the user encoded on one or more CD-ROM 225 and read via the corresponding drive 212, 30 or alternatively may be read by the user from the networks 220 or 222. Still further, the software can also be loaded into the computer system 200 from other computer readable media. Computer readable storage media refers to any storage 18 medium that participates in providing instructions and/or data to the computer system 200 for execution and/or processing. Examples of such storage media include floppy disks, magnetic tape, CD- ROM, a hard disk drive, a ROM or integrated circuit, USB memory, a magneto-optical disk, or a computer readable 5 card such as a PCMCIA card and the like, whether or not such devices are internal or external of the computer module 201. Examples of computer readable transmission media that may also participate in the provision of software, application programs, instructions and/or data to the computer module 201 include radio or infra-red transmission channels as well as a network connection 10 to another computer or networked device, and the Internet or Intranets including e-mail transmissions and information recorded on Websites and the like. The second part of the application programs 233 and the corresponding code modules mentioned above may be executed to implement one or more graphical user interfaces (GUIs) to be rendered or otherwise represented upon the 15 display 214. Through manipulation of typically the keyboard 202 and the mouse 203, a user of the computer system 200 and the application may manipulate the interface in a functionally adaptable manner to provide controlling commands and/or input to the applications associated with the GUI(s). Other forms of functionally adaptable user interfaces may also be implemented, such as an audio 20 interface utilizing speech prompts output via the loudspeakers 217 and user voice commands input via the microphone 280. Fig. 4B is a detailed schematic block diagram of the processor 205 and a "memory" 234. The memory 234 represents a logical aggregation of all the memory modules (including the HDD 209 and semiconductor memory 206) that 25 can be accessed by the computer module 201 in Fig. 4A. When the computer module 201 is initially powered up, a power-on self test (POST) program 250 executes. The POST program 250 is typically stored in a ROM 249 of the semiconductor memory 206. A hardware device such as the ROM 249 is sometimes referred to as firmware. The POST program 250 30 examines hardware within the computer module 201 to ensure proper functioning, and typically checks the processor 205, the memory (209, 206), and a basic input output systems software (BIOS) module 251, also typically stored in the ROM 19 249, for correct operation. Once the POST program 250 has run successfully, the BIOS 251 activates the hard disk drive 210. Activation of the hard disk drive 210 causes a bootstrap loader program 252 that is resident on the hard disk drive 210 to execute via the processor 205. This loads an operating system 253 into the 5 RAM memory 206 upon which the operating system 253 commences operation. The operating system 253 is a system level application, executable by the processor 205, to fulfil various high level functions, including processor management, memory management, device management, storage management, software application interface, and generic user interface. 10 The operating system 253 manages the memory (209, 206) in order to ensure that each process or application running on the computer module 201 has sufficient memory in which to execute without colliding with memory allocated to another process. Furthermore, the different types of memory available in the system 200 must be used properly so that each process can run effectively. 15 Accordingly, the aggregated memory 234 is not intended to illustrate how particular segments of memory are allocated (unless otherwise stated), but rather to provide a general view of the memory accessible by the computer system 200 and how such is used. The processor 205 includes a number of functional modules including a 20 control unit 239, an arithmetic logic unit (ALU) 240, and a local or internal memory 248, sometimes called a cache memory. The cache memory 248 typically include a number of storage registers 244 - 246 in a register section. One or more internal busses 241 functionally interconnect these functional modules. The processor 205 typically also has one or more interfaces 242 for communicating 25 with external devices via the system bus 204, using a connection 218. In computer operated embodiments of the invention processor 205 may receive the differential pressure monitored by gauge 3 as an input and to send an output to the automatic valve 18 to vary the amount of stored compressed air released. 30 The application program 233 includes a sequence of instructions 231 that may include conditional branch and loop instructions. The program 233 may also include data 232 which is used in execution of the program 233. The instructions 20 231 and the data 232 are stored in memory locations 228-230 and 235-237 respectively. Depending upon the relative size of the instructions 231 and the memory locations 228-230, a particular instruction may be stored in a single memory location as depicted by the instruction shown in the memory location 5 230. Alternately, an instruction may be segmented into a number of parts each of which is stored in a separate memory location, as depicted by the instruction segments shown in the memory locations 228-229. In general, the processor 205 is given a set of instructions which are executed therein. The processor 205 then waits for a subsequent input, to which it 10 reacts to by executing another set of instructions. Each input may be provided from one or more of a number of sources, including data generated by one or more of the input devices 202, 203, data received from an external source across one of the networks 220, 202, data retrieved from one of the storage devices 206, 209 or data retrieved from a storage medium 225 inserted into the corresponding 15 reader 212. The execution of a set of the instructions may in some cases result in output of data. Execution may also involve storing data or variables to the memory 234. The disclosed arrangements use input variables 254 that are stored in the memory 234 in corresponding memory locations 255-258. The described 20 arrangements produce output variables 261 that are stored in the memory 234 in corresponding memory locations 262-265. Intermediate variables may be stored in memory locations 259, 260, 266 and 267. The register section 244-246, the arithmetic logic unit (ALU) 240, and the control unit 239 of the processor 205 work together to perform sequences of 25 micro-operations needed to perform "fetch, decode, and execute" cycles for every instruction in the instruction set making up the program 233. Each fetch, decode, and execute cycle comprises: (a) a fetch operation, which fetches or reads an instruction 231 from a memory location 228; 30 (b) a decode operation in which the control unit 239 determines which instruction has been fetched; and (c) an execute operation in which the control unit 239 and/or the ALU 240 21 execute the instruction. Thereafter, a further fetch, decode, and execute cycle for the next instruction may be executed. Similarly, a store cycle may be performed by which the control unit 239 stores or writes a value to a memory location 232. Each step 5 or sub-process in the method of the invention is associated with one or more segments of the program 233, and is performed by the register section 244-1047, the ALU 240, and the control unit 239 in the processor 205 working together to perform the fetch, decode, and execute cycles for every instruction in the instruction set for the noted segments of the program 233. 10 One or more client computers 250, 251 may be connected to the communications network 220 as seen in Fig. 4A. Each of the computers 250, 251 has a similar configuration to the computer module 201 and corresponding peripherals. The method of the invention may alternatively be implemented in 15 dedicated hardware such as one or more integrated circuits performing the functions or sub functions of the described methods. Such dedicated hardware may include graphic processors, digital signal processors, or one or more microprocessors and associated memories. The present invention is of significant advantage because it extends the 20 time a refuge chamber is able to sustain life, importantly extending the rescue window and improving the probability that rescue can be performed or the emergency passes without loss of life. By providing a positive pressure the present inventors have provided a surprisingly novel and inventive means for protecting the integrity of the 25 breathing air in a refuge chamber. Furthermore, the invention makes efficient use of the stored compressed air that is used to protect this integrity which extends the period for which the refuge chamber can sustain life. Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one 30 embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments 22 exemplified without departing from the scope of the present invention. All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference. 5

Claims (5)

1. A device for maintaining breathable air in a refuge chamber, the device comprising: 5 a gauge to monitor differential pressure between inside the refuge chamber and outside the refuge chamber; a detector to detect one or more hazardous or harmful substance inside the refuge chamber; a compressed air storage bank to maintain the differential pressure at a 10 desired positive differential level and to reduce the level of at least one of a respective one or more detected hazardous or harmful substance below a set level by varying an amount of stored compressed air released into the refuge chamber. 15

2. A method for maintaining breathable air in a refuge chamber, the method comprising: monitoring differential pressure between inside the refuge chamber and outside the refuge chamber; detecting with a detector an amount of one or more hazardous or harmful 20 substance inside the refuge chamber; varying an amount of stored compressed air released into the refuge chamber in response to the detected amount of the one or more hazardous or harmful substance to maintain the differential pressure at a desired positive differential pressure and to reduce the amount of a respective one 25 or more detected hazardous or harmful substances below a set level to thereby maintain breathable air in a refuge chamber.

3. The device of claim 1 further comprising a solenoid valve operated by the detector to vary the amount of stored compressed air released or the method of 30 claim 2 wherein the amount of stored compressed air is varied by a solenoid valve operated by the detector. 24

4. The device of claim 1 or claim 3 wherein the detector comprises a carbon monoxide sensor or the method of claim 2 or claim 3 wherein the detecting comprises sensing with a carbon monoxide sensor an amount of carbon monoxide. 5

5. The device of any one of claims 1, 3 or 4 further comprising a manually operated valve that is used to increase or decrease the rate of flow of compressed air into the refuge chamber or the method of any one of the claims 1, 3 or 4 further comprising manually increasing or decreasing the rate of flow of 10 compressed air into the refuge chamber by manually operating a valve.