Abstract:
Mobile fire-fighting systems and a method of producing breathable fire-suppression compositions are provided for extinguishing fires in buildings, and other human occupied structures, being also effective in suppressing fires under ruins of collapsed buildings. The systems employ a transportable high-pressure container having the breathable composition or nitrogen gas, or a liquid nitrogen container, vaporizer and a mixing chamber, wherein a vaporized nitrogen gas is mixed with an ambient air in order to produce said breathable fire-suppression composition. Refilling stations are provided for refilling the mobile systems with said composition, nitrogen gas or liquid nitrogen, all being generated at site from the ambient air. The method of producing said composition at a fire site employs mixing of nitrogen gas with ambient air or, alternatively, vaporizing of liquid nitrogen in necessary quantities and mixing it with ambient air in provided proportions. A method of delivery of the breathable fire-suppressive composition inside a building on fire is provided as well. The systems are also suitable for installation as a stationary fire-suppression system for a building or other structure. A breathable fire-suppression composition is provided for use in said mobile systems, said composition having an oxygen content below 16% or from 10% to 12% for the majority of civil applications.

Description:
This application is a continuation in part of U.S. application Ser. No. 09/750801 “Hypoxic Fire Prevention and Fire Suppression Systems and Breathable Fire Extinguishing Compositions for Human Occupied Environments” filed Dec. 28, 2000 and U.S. application Ser. No. 09/854108 “Hypoxic Fire Prevention and Fire Suppression Systems with Breathable Fire Extinguishing Compositions for Human Occupied Environments” filed May 1, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention introduces the method, equipment, and composition for fighting fires in human-occupied spaces, using a mobile system that can produce, store and deliver hypoxic fire-extinguishing agent into any enclosed environment in order to instantly extinguish an ongoing fire and to prevent fire from starting again. 
     The goal of this invention is to provide superior solution for current firefighting vehicles that use water or foam for fighting fires. 
     With its mode of action based on the delivery and release of breathable hypoxic fire-suppressive gas mixture, this human-friendly system is completely non-toxic and entirely self-sustaining. Consequently, it is ideally suited for fighting fires in buildings of any type and all other applications where current firefighting vehicles are used. This invention is an important addition and improvement of the Fire Prevention and Suppression System (FirePASS™) described in earlier patent applications provided above. 
     DESCRIPTION OF PRIOR ART 
     Residential and industrial fires happen every minute and firefighters around the globe risk their lives while trying to extinguish them mostly with the oldest and primitive method of spraying water. 
     Modern firefighting vehicles can provide either water or foam, which is not efficient and creates damage to equipment and property. This inefficiency was demonstrated recently by the daylong efforts of extinguishing fire in Pentagon building after terrorist attack on Sep. 11, 2001. 
     Water or foam are especially inefficient in fighting fires under collapsed buildings, which usually happens after earthquakes and explosions. Hundreds of firefighters tried for over three weeks to extinguish multiple fires under World Trade Center in New York, collapsed after terrorist attack on the same date. And there is always a risk that survivors under rubble could drown in water supplied by fire engines. Many fires there were started and maintained by multiple gas leakages under ruins, which cannot be extinguished using current methods. 
     The invented Mobile Firefighting Unit (MFU) can extinguish similar fires within minutes by flooding ruins with breathable hypoxic agent that would instantly suppress local fires while allowing survivors to breath. 
     MFU can be used in any type of building and structure, providing instant fire suppression and, most importantly, safe human-breathable environment (clinical studies have proven that long term exposure to a hypoxic environment has significant health benefits). 
     Hypoxic breathable gas mixture (fire suppressive agent) can be inexpensively produced in necessary quantities through the extraction of oxygen from ambient air, which is provided by the Hypoxic Generator described in previous applications. Hypoxic fire-extinguishing agent is stored in a high-pressure container and can be released when needed at any location. Alternatively, breathable hypoxic agent can be produced at site by mixing ambient air with nitrogen, delivered in a liquid form in a mobile container and evaporated in necessary quantities through forced heating. 
     SUMMARY OF THE INVENTION 
     The principal objects of this invention are as follows: 
     A method for producing, storing, transporting and releasing breathable hypoxic fire-extinguishing agent inside human-occupied environments. 
     The provision of equipment that can produce, store, transport and release said hypoxic breathable fire-extinguishing agent at demand. Such equipment employs the processes of molecular-sieve adsorption, membrane-separation, cryogenic distillation and other oxygen extraction technologies for producing said agent. 
     The provision of mobile equipment that employs a high-pressure gas storage container in order to store said agent and a motorized frame or truck to transport it. The release of said agent on fire site is accomplished via hose, piping or tubing delivering said agent from the high-pressure container to the location of fire. 
     The provision of mobile equipment and a method to instantly produce said agent at fire site by evaporating liquid nitrogen and mixing nitrogen gas with ambient air. This equipment employs a liquid nitrogen storage container, vaporizer, air supply pump and mixing chamber, all being installed on a motorized frame or truck in order to transport it. The release of said agent on fire site is accomplished via hose, piping or tubing delivering produced agent from the mixing chamber to the location of fire. 
     The provision of mobile equipment and a method to instantly produce said agent at fire site by mixing nitrogen gas with ambient air in specific proportions. This equipment employs a high-pressure nitrogen gas storage container, air supply pump and a mixing chamber, all being installed on a motorized frame or truck in order to transport it. The release of said agent on fire site is accomplished via hose, piping or tubing delivering produced agent from the mixing chamber to the location of fire. 
     The provision of mobile equipment and a method to instantly produce a fire-suppressive, oxygen-depleted atmosphere, where people can safely breath (without respiratory-support means). This can be accomplished by the releasing the hypoxic agent inside a building or other object on fire and creating fire-suppressive atmosphere having an oxygen content ranging from 10% to 16%. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 presents an illustrative view of the MFU having a high-pressure container with hypoxic agent (MFU-HP). 
     FIG. 2 illustrates schematically a working principle of the MFU-HP system. 
     FIG. 3 presents an illustrative view of the MFU having liquid nitrogen container, vaporizer and mixing chamber for producing hypoxic agent (MFU-L). 
     FIG. 4 shows schematically a working principle of the MFU-L system. 
     FIG. 5 presents an illustrative view of the MFU having a high-pressure container with hypoxic agent (MFU-HPN). 
     FIG. 6 illustrates schematically a working principle of the MFU-HPN system. 
    
    
     DESCRIPTION OF THE INVENTION 
     This invention is based on the discovery of the Phenomenon of Ignition Suppression and Combustion Elimination in hypoxic breathable air and the Hypoxic Fire Prevention and Suppression System (FirePASS™), being described in previous patent applications provided above. 
     FIG. 1 presents an illustrative view of the first preferred embodiment 10 of the Mobile Firefighting Unit for extinguishing fires in general applications, including private homes, high-rise apartment and office buildings, industrial facilities, etc. This system utilizes High-Pressure Hypoxic Agent and will be referred further as MFU-HP. 
     MFU-HP is assembled on the base of a standard truck  11  with a loading capacity of approximately 20 tons. A high-pressure container  12  holds 20 m3 of the Breathable Hypoxic fire-extinguishing Agent (BHA) compressed up a pressure of 400-500 bar. BHA is produced from ambient air using oxygen extraction (as described in previous patent applications) and generally contains 10%-12% of oxygen. The oxygen content may vary in some special application from 1%-10% (e.g. in oilfield and forest fires) up to 16% (long-term support of trapped survivors where danger of a secondary fire or explosion persists). 
     Container  12  is connected via high-pressure conduit  13  to distributor  14  that contains a pressure reducing system (shown on FIG.  2 ), control instruments panel  15  and a distribution manifold having multiple distribution outlets  16 . Gas delivery hoses  17  can be attached, via high-pressure “quick-connect” connectors, to the outlets  16 , which will allow delivering reduced-pressure BHA into a building or other object on fire. 
     Container  12  is equipped with a refilling inlet  18 , through which it can be quickly refilled from a larger gas storage container  20  at the station or from a mobile refilling station. Refilling procedure is very simple: a secure high-pressure connector  19  is attached to container  12  and release valve  21  is opened. After a gas pressure in both containers is equalized, valve  21  can be closed and connector  19  can be disconnected from inlet  18  having a secure one-way valve that opens only when higher pressure from outside is applied. An additional compressor may be employed here in order to increase the refilling pressure. 
     Storage container  20  is constantly kept under 500 bar pressure and refilled by compressor  22  and hypoxic generator  23 , available from FirePASS Inc. All three components, container  20 , compressor  22  and hypoxic generator  23  can be assembled on a firefighters station or on a mobile platform. Such a mobile platform holds up to 80 cubic meters of the compressed BHA and can be connected to one or more MFU at a fire site in order to provide larger quantities of BHA in case of an extremely large fire. 
     One MFU-HP can provide 10,000 cubic meters of BHA, which is sufficient to flood a 10-story building with 20×20 meters wide floors. The mobile gas storage platform can deliver 40,000 cubic meters of BHA calculated at standard atmospheric pressure. 
     FIG. 2 illustrates schematically the working principle of the MFU-HP system. When in use, the pressure-reducing release valve or reductor  24  opens by a signal from control unit  14  and the system provides compressed BHA into gas tank  25  where it is kept under reduced pressure controlled by pressure transducers and gauges  15 . When a hose  17  is attached to an outlet  16 , valve  26  automatically opens releasing BHA into hose  17  that delivers agent to the fire site. Reductor  24  is preset to automatically maintain pressure in the tank  25  at desired level of approximately 50 bar. When all outlets  16  are in operation and all valves  26  open, reductor  24  allows more flow into tank  25 , in order to keep it at the preset pressure. When the system is shut down, reductor  24  automatically closes preserving the rest of the BHA in container  12 . 
     The MFU-HP system is refilled when needed from a stationary gas storage container  20  at the firefighter&#39;s station or from a similar mobile unit. The BHA producing components  22  and  23 , in smaller size, can be installed on the same MFU truck  11 , which is not quite efficient, since in would take many hours to refill container  12 . Therefore it was decided to make refilling station  20 - 22 - 23  separate from the MFU-HP. 
     Hypoxic generator  23  produces the breathable hypoxic agent. It consists of a compressor that intakes ambient atmospheric air and sends it in compressed form into air-separation module where a part of the oxygen is extracted. The oxygen-enriched gas mixture can be either disposed into the atmosphere or, preferably, sent to a fuel cell that can generate electricity for the station&#39;s needs. 
     BHA produced by Hypoxic generator  23  is further compressed by compressor  22  up to 500 bar and sent for storage into gas storage container  20 . 
     Oxygen-extraction technology is well known to those skilled in the art and may employ oxygen-enrichment membranes and pressure-, vacuum- or temperature-swing adsorption or other appropriate processes. Suitable hypoxic generators and/or air-separation modules are available from Hypoxico Inc. and FirePASS Inc. in New York. 
     The product remaining after oxygen extraction is an oxygen-depleted (hypoxic) gas mixture or BHA, containing less than 16% of oxygen, more than 84% of nitrogen and traces of other (mostly noble) atmospheric gases and water vapor. For the majority of civil applications the oxygen content in the product should be in the range from 10% to 14% and nitrogen content between 90% and 86%. This product is actually the Breathable Hypoxic Fire Extinguishing Composition described in the previous patent applications provided above. 
     The Breathable Hypoxic Fire Extinguishing Composition can be also produced at the refilling station by simply mixing nitrogen gas with ambient air at necessary proportions. For instance, mixing equal parts of nitrogen gas and air can make a composition with 10.5% oxygen content. This technology is similar to the system described further according to FIG. 5 and 6. 
     FIG.  3  and FIG. 4 present an illustrative view and a working principle of the second preferred embodiment  30  of the invented system—MFU-L having liquid nitrogen container  32  mounted on the chassis of the truck  31 . Container  32  is build as a dewar-type vessel with a refilling inlet  33  and can hold up to 20 cubic meters of liquid nitrogen that is constantly kept under its boiling point temperature of −195.8° C. by an optional cryogenic cooler  34  in order to prevent evaporation of nitrogen or simply by adding more liquid nitrogen at a much lower temperature. MFU-L must be always fully refilled with liquid nitrogen. In some applications, small quantities of liquid nitrogen can constantly circulate through cryogenic cooler  34  and back into container  32 . Cryogenic coolers of different types are available from a number of manufacturers. Stirling-type gas power and liquid power coolers or turboexpander coolers are preferred. Cryogenic cooler  34  is preferably installed separately at the fire station since it is not needed during firefighting operation. Cryogenic cooler  34  can also refill container  32  with liquid nitrogen in cases where a larger cryogenic nitrogen plant is not available. However, it is highly recommended to have such liquid nitrogen plant  49  with a larger storage container  48  (e.g. 500 m3) that can provide for quick refilling of all MFU-L at the station or in a particular urban area. At the fire station, the MFU-L can be directly coupled with the refilling container  48  or straightly with the liquid nitrogen plant  49 . This way, there is no need in cryogenic cooler  34  since the level of liquid nitrogen in container  32  will be maintained automatically by its refilling from container  48  or from plant  49 . Suitable liquid nitrogen plants are available from a number of manufacturers and are offered by FirePASS Inc. 
     The working principle of the MFU-L can be described as follows. In order to generate BHA at the fire site, the pump  35  pumps liquid nitrogen from container  32  into evaporator  36 , where it is transformed into nitrogen gas. Different types of liquid nitrogen evaporators are available on the market, from diesel-fired, non-fired to heat-recovery vaporizers. The most preferred type of an evaporator for this invention is a non-fired or a heat recovery system that utilizes the heat from the burning diesel fuel used by the MFU truck. This type of evaporator can produce 200 m3/min of nitrogen and will be available from FirePASS Inc. in New York. Heating systems employing microwave radiation or electric induction are also suitable for this application. 
     Nitrogen gas from evaporator  36  enters mixing chamber  37  where it is mixed with an ambient air supplied by a blower or compressor  38  having an air intake filter  44 . If nitrogen and air are mixed in equal quantities, they will provide BHA with an oxygen content of 10.5%, which is acceptable for most applications. However, for residential fires, it is recommended to keep the oxygen content in BHA around 12%, which can be achieved by mixing 100 volumes of nitrogen with 116 volumes of air. Necessary mixing proportions can be easily preset and maintained manually or automatically by a computerized control system  39  that can adjust airflow and/or pressure from the air pump  38  according to the data provided by oxygen transducers  40  installed in the distribution unit  41  having gas outlets  42 . 
     MFU-L components  35 ,  36 ,  37  and  38  are assembled in box  43  having outside air-intake filter  44 , BHA outlet  45  and liquid nitrogen supply conduit  46 . The components  39 ,  40  and  42  are assembled in the distribution unit  41  having additionally pressure gages, temperature transducers and other necessary instruments. Gas delivery hoses  47  are equipped with quick-disconnect fittings for instant connection with distribution outlets  42 . On the other end hose  47  is equipped with a heat resistant ceramic or metal nozzle that can be inserted through a window or other opening into a building on fire. The MFU of both types should be equipped with a skylift-type elevating machine that can deliver and insert hose  47  into any floor of a high-rise building or structure. 
     The refilling station of the MFU-L components  48 ,  49  and optional component  34  are installed separately at a fire station. FirePASS Inc. offers suitable dewar-type liquid nitrogen storage containers and liquid nitrogen generating plants capable of producing 2, 5 and 7.5 ton per day. These plants are available in compact containers, both truck mounted and stationary types. 
     The MFU-L can carry 20 m3 of liquid nitrogen that will provide 18000 m3 of nitrogen gas and is capable of delivering 45,000 m3 of BHA at the site without refilling. This quantity of the BHA is sufficient to completely exchange atmosphere in a 50-story high-rise, removing smoke and other toxic gases and providing safe, breathable fire-suppressive environment. Gas delivery hoses inserted in the floors on fire would provide safe BHA that will extinguish any fire in minutes and without any damage to people, property or equipment. 
     FIG. 5 shows third embodiment of the MFU, which is a system (MFU-HPN) that employs a high-pressure container, similar to MFU-HP, filled with a nitrogen gas instead of the BHA and utilizing the air-mixing feature of the MFU-L. 
     The MFU-HPN system  50  consists of a truck  51 , a high-pressure nitrogen gas container  52  and a mixing-and-distribution unit  55 . The working principle of this embodiment is presented on FIG.  6 . The nitrogen gas, being held in container  52  under 500 bar pressure, is released, via outlet  53  and pressure reducing device or reductor  57 , into mixing chamber  58 . An air pump  59  draws ambient air through intake  54  and supplies it into mixing chamber  58  wherein the air and nitrogen gas mix in necessary proportions that can be regulated from control panel  15  installed on the front of the unit  55 . Mixing of equal volumes of air and nitrogen would provide a breathable fire-suppressive composition having an oxygen content of 10.5%, which is suitable in most applications. Further said composition is distributed, via multiple gas outlets  16  and valves  26 , into gas delivery hoses  17  that deliver it to the fire location. 
     The components  18 ,  19 ,  20 ,  21  and  22  of the refilling station are the same as shown on FIG. 1 and 2. However, the hypoxic generator  23  is replaced in this embodiment with a nitrogen generating plant  56  that can employ molecular sieve adsorption, membrane separation, cryogenic distillation and other air separation technologies in order to supply the refilling station with nitrogen. Nitrogen gas is compressed up to 500 bar by a multistage compressor  22  and is stored in a storage container  20  having release valve  21  for refilling of MFU. 
     The MFU-L system  30  and MFU-HPN system  50  (excluding transporting vehicles  31  or  51 ) can be also installed on the ground or a roof of a building and utilized as on-site fire-suppression system. Such stationary systems can be extremely effective in all kinds of buildings, tunnels, mines and other human-occupied facilities and enclosed environments. In this case multiple gas outlets  42  should be connected to stationary pipes  47  leading to different floors, levels or areas of a building or structure. This will allow delivering BHA directly to the location where fire or smoke was detected. 
     In order to improve effectiveness of the MFU, all residential and office buildings should have installed similar distribution piping leading to different floors, levels or areas of a building with clearly marked inlets accessible from the street. This will allow firefighters to connect MFU gas hoses to the pipes leading to the floors or levels affected by fire. BHA supplied directly to the right location would extinguish any fire within minutes while allowing people to breath. The installation of such piping does not require much expense, but would greatly improve building&#39;s fire safety, provided the MFU are deployed in the area.