US2341437A - Fire-extinguishing method and apparatus - Google Patents

Description

Feb. 8, 1 944. c. A. G'Efrz 2,341,437

A FIRE `Ifl'l'INGUISHING METHOD AND APPARATUS Filed April 24. 194s llllL. LAUNU'I'UJE Patented Feb. 8, 1944 UNITED STATES Q'Ciulbal muuuy PATENT OFFICE FIRE-EXTINGUISHING METHOD AND APPARATUS United States Application April 24, 1943, Serial No. 484,405

Claims.

This invention relates to a new and useful method and apparatus for extinguishing res, and deals more particularly with the extinguishment of res involving light metals, such as magnesium, and their alloys while they are in mass or bulk form, such as ingots, blocks, castings, plates, chips or shavings, and when they are powdered or in a molten state.

Due to the4 recent tremendous increase in the use of light metals for fabricating munitions,

and the like, considerable research time has been devoted to studies of extinguishing methods, apparatus, and materials in an effort to develop practical ways and means for combatting the res which occur rather frequently While such metals are being processed.

It would appear from the published reports covering this research work that most of the efforts have been directed toward the use of materials which must be applied manually, or by means of hand equipment. Because of the high` burning temperature of magnesium, for example, it is diflcult for a person to approach even a small re close enough to effectively apply the extinguisher With hand equipment. When a fire of any substantial size is encountered, hand applicators are all but worthless.

Another characteristic of the extinguishing materials and methods that have been recommended is they are directed solely to the extinguishment of the light metal res and are ineffective for extinguishing fires that may have spread to other, more conventional, combustible materials.

It is the primary object of this invention to provide a method of extinguishing fires involving light metals, and particularly magnesium.

A further important object of the invention is the provision of a method which is capable of extinguishing light metal fires of a size that cannot be effectively treated With hand or small portable equipment.

Still another important object of the invention is to provide a xed fire extinguishing system which is particularly adapted for quenching or extinguishing burning magnesium, or other light metals, and which is further capable of extinguishing res that may have spread to other nearby combustible materials.

A more specic object of the invention is to provide a method and apparatus for eecting extinguishment of magnesium, or other light metal, fires by rst creating, in the enclosed space in which the re is burning, a moderate Cil dioxide vapor, and While continuing to build up the concentration of gas to a percentage that is adequate to effect extinguishment of Class B combustibles, spraying a suitable high-fiash-point liquid over the exposed surface of the burning metal to create a blanket which will exclude oxygen from the iire and will effect cooling of the metal to a temperature below that at which it will burn.

Another object of the invention is the provision of an automatically operable fixed system for extinguishing light metal fires.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a diagrammatic view of a lire extinguishing system which has Ibeen installed to protect light metals, such as magnesium, while being handled or processed in an enclosed space, and

Figure 2 is a wiring diagram for the control instrumentalities of the re extinguishing system shown in Fig. 1.

In the drawing, wherein for the purpose of illustration is shown the preferred embodiment of this invention, and first particularly referring to Fig. 1, the reference character 5 designates an enclosed space which may take the form of a complete building, or a 'closed off room, compartment or booth which forms a part of or is located Within a larger building. The disclosure, therefore, is merely to be construed as representative of any enclosed space. To create the type of hazard that is to be protected by the method and apparatus embodying this invention, the enclosed space 5 has therein a quantity of a light metal, such as magnesium, which may lbe in mass or bulk form as ingots, blocks, castings, plates, chips or shavings, and which also may be in powdered form or in a molten state. This metal, while in storage or while being processed, is generically represented or depicted by the form that is identiiied by the reference character 6.

Basically, the method of this invention which is directed to the extinguishment of a re that is consuming the light metal 6 consists of discharging into the enclosed space 5 an inert gas for the purpose of totally flooding the space. The object of totally flooding the space is to build up a concentration of the inert gas which will concentration of an inert gas, such as carbon be suiiicient to effect extinguishment of a fire c" s i that is consuming a Class B combustible material; i. e., a flammable fluid. Carbon dioxide vapor is preferred as the inert gas that should be used to effect total flooding of the enclosed space 5. A final or ultimate concentration of approximately 50% carbon dioxide vapor is entirely adequate to extinguish a flammable fluid fire.

Carbon dioxide is generally recognized as an extinguisher which is not effective for quenching or putting out fires involving light metals, such as magnesium. This is due to the fact that the temperature of the flame of burning magnesium is quite high and it results in breaking down the carbon dioxide to oxygen and carbon monoxide. 'Ihe oxygen that is thus liberated cooperates or combines with the magnesium to further upset the equilibrium with the result that the magnesium continues to burn.

It has been determined, however, that magnesium does not burn any more vigorously in a still atmosphere that includes a concentration of from 20 to 30 percent carbon dioxide vapor than it does in a still atmosphere of air alone. Therefore, the inert gas, which is preferably carbon dioxide vapor, is discharged into the enclosed space 5 in such a manner that it will not disturb the atmosphere in the enclosed space sufficiently to create a vigorous or pronounced circulation or turbulence. Additionally, the carbon dioxide vapors should not be released at one or more points which are sufficiently closely positioned with respect to the burning metal to cause the vapors to directly impinge any surface of the metal.

After the carbon dioxide concentration has been built up to a value of from 20 percent to 30 per cent, the metal 6 is sprayed with a highash-point fluid, such as a petroleum or a vegetable oil, for the purpose of creating a blanket which will completely cover all of the exposed surfaces of the metal. This blanket will function to smother the re as a result of completely shutting off the surrounding atmosphere from the magnesium. The fluid of the smothering blanket also performs the function of cooling the metal down to a temperature at which it will no longer continue to burn.

Extensive tests have proved that vegetable oils, lubrication oils, kerosene, and even gasoline can be employed to create this smothering and cooling blanket. The more viscous liquids, such as soy bean oil and lubrication oils, as most desirable, however, because they will not vaporize so easily and their higher surface tension will cause them to cling to the surfaces of the metal to form a more perfect, effective blanket for excluding the oxygen of the surrounding atmosphere from the metal.

During the period while the fluid blanket is being applied to the burning metal, the flooding of the enclosed space with the inert gas is continued and is timed so that a concentration of approximately 50 percent is obtained by the time the smothering and cooling blanket is completely formed.

The extinguishment of the light metal fire, therefore, is accomplished by the smothering and cooling action of the uid blanket while the vapors, released from the iiuid blanket by the temperature of the burning metal, will not ignite and burn because of the inert gas atmosphere that surrounds the iirerzone. It will be appreciated, of course, that before the vapors of fiammable fluids will ignite they must be mixed with sufficient oxygen to produce a combustible fuel.

The high concentration of inert gas in the surrounding atmosphere prevents a combustible fuel mixture from being formed. Of course, if a combustible fuel mixture is formed during the initial application period of the fluid blanket and this combustible fuel does ignite, it will be extinguished as the inert gas concentration builds up to a percentage which will prevent the formation of any additional combustible fuel mixture.

If the intensity of the metal fire has caused flame to spread to any other combustible objects located in the enclosed space or to the floor or walls and ceiling of said space, the total flooding of the space with the inert gas will cause these additional fires to be extinguished. This would not be the case if the burning metal were extinguished with a medium which was merely applied to the surfaces of the metal and which was intended to effect its extinguishment merely as a result of its contact with the metal surfaces.

The apparatus employed for carrying out the above described re extinguishing method is adequately disclosed in Figs. l and 2. The inert gas, which is preferably carbon dioxide vapor, employed for totally ooding the enclosed space 5 to the desired percentage of concentration is obtained from the storage source which is designated by the reference character 1. This storage source may take the form of a bank of cylinders or a single tank. The carbon dioxide may be stored as a vapor or as a liquid. If it is stored as a liquid, it may be drawn off in that form and converted to a mixture of vapor and snow as it is discharged into the enclosed space 5. If the carbon dioxide is stored as a liquid, vapors only may be withdrawn from the vapor space or spaces of the tank or cylinders. Of course, if the carbon dioxide is stored as a vapor, it will be withdrawn from the source and delivered to the enclosed space 5 without any change in phase or form. It is preferred, however, that the carbon dioxide be stored as a liquid in an insulated tank and maintained at a predetermined subatmospheric temperature, and its corresponding vapor pressure, in accordance with the teachings of Patent No. 2,202,343, issued to Eric Geertz on May 28, 1940. By obtaining the carbon dioxide vapors employed for totally flood` ing the enclosed space 5 from a source of low temperature and low pressure liquid carbon dioxide, the vapors will be discharged into the space at a lower velocity than would be practical if the carbon dioxide were stored as a liquid in an uninsulated, unrefrigerated tank or a bank of cylinders. This lower velocity of discharge results from the storage of the liquid at a low pressure and is highly desirable in order to prevent the creation of turbulence within the space. The temperature of the discharged vapors that are obtained from a low temperature source of supply will be lower than from a high temperature source of supply and will have the desirable effect of supplementing the cooling action of the smoothering blanket with reference to the burning metal. Additionally, low temperature carbon dioxide vapors will prevent ignition of any combustible vapor-oxygen fuel mixture that may be formed by cooling it to a temperature below its ignition point.

The carbon dioxide vapor or liquid is withdrawn from the source of supply 'l through the pipe line 8 and is discharged into the enclosed space 5 by the devices 9. A shut-off valve I0 is provided in this pipe line. This valve normally is locked in its open condition. Its function -vices, suitable switches 20 will be provided in the enclosed space is to enable the carbon dioxide to be retained in the source of supply 1 in the event it becomes necessary to service or replace any of the control and discharge equipment downstream from the valve I0. 'I'he pipe line 8 is provided with a discharge control valve II which is normally closed and is only opened when the carbon dioxide is to be discharged into the enclosed space for totally iiooding the same. This carbon dioxide control valve II must be bubble tigh so as to prevent leakage of carbon dioxide to the discharge devices 9. It may be manually operable if desired but it preferably should be of a type which will permit it to be opened and closed as a result of energizing and de-energizing an electromagnet device. An appropriate valve structure for this type of service is disclosed in Fig. 3 of the copending application Ser. No. 459,994, led in the name of Charles A. Getz, on September 28, 1942.

The blanket forming liquid supply is obtained from the storage tank I2. It is drawn from this tank through the pipe line I3 for delivery to the spray nozzles I4. These spray nozzles should be provided in proper number and should be so arranged with respect to the kind and type and arrangement of light metal to be protected as to apply the necessary solid or continuous blanket to all of the exposed surfaces. A valve I5 is provided in this pipe line I3 for controlling ow therethrough. This valve, also, may be manually controlled if desired but it is preferred that it be operable by suitable electrical means which will effect opening and closing of the valve as a result of being energized and deenerglzed. This valve I5 may be of the same construction as the carbon dioxide control valve II.

The iiuid stored in the tank I2 is to be expelled therefrom by carbon dioxide vapor pressure which is delivered to the top of the tank I2 from the pipe line 8 through the branch line I6. A valve I1 is provided in this branch line I 6 for controlling the flow of carbon dioxide vapor to the storage tank I2. This valve I1 may either be manually controlled or electrically controlled in the same manner as valves II and I5.

If the valves I5 and I'I are electrically controlled or operated, it is possible to prevent a false closing of the circuits to the electrical devices of these two valves, which might result from a short circuit, by having a carbon dioxide pressure operated switch I8 connected in series in the circuit or circuits for these two valves. This pressure operated switch I8 is supplied with carbon dioxide by the branch pipe line I9 which is connected to the carbon dioxide line 8 downstream of its control valve II.

It will be appreciated, therefore, that the electric circuits for the actuating means of the valves I5 and I1 cannot be completely closed until switch I8 is closed and that this latter switch is not closed until suiilcient carbon dioxide pressure to actuate the switch I8 is provided in the branch pipe line I9. As this branch pipe line is only supplied with carbon dioxide pressure when the carbon dioxide discharge control valve I I is opened, it will be appreciated that the valves I5 and I1 cannot be electrically energized and opened until the control valve I l is energized and opened.

When the fire extinguishing system is to be automatically rendered operative as a result of actuation of temperature operated detection deheat responsive, thermostatic 5 in proper operative relation to the metal hazard 6. Actuation of either one of these thermostatic switches 20 will result in initiating the operation of the automatic electric control mechanism of the system.

A pre-discharge alarm 2I is provided in the enclosure 5 for the purpose of warning any oc- Y cupants of this space in advance of actual release of any carbon dioxide vapors into the space. This pre-discharge warning should provide ample time for the occupants of the enclosed space to lelave the same through the exit door, or the like, 2

Figure 2 discloses the wiring diagram for the control mechanism which will provide the proper timed opening and closing of the valves II, I5 and I1 to bring about the desired sequence of discharge of the carbon dioxide vapors into the enclosed space 5 and the discharge of the uid from the spray heads I4 onto the metal hazard 6 after the desired percentage or partial concentration of carbon dioxide has been created in the space. The three valves I I, I5 and I1, the carbon dioxide vapor pressure operated switch I8, the temperature responsive circuit closing devices 26 and the pre-discharge alarm 2| are all diagrammatically disclosed in the right hand portion of Fig. 2.

The electric power supply lines 23 and 24 extend from a suitable source to the control mechanism. Supply wire 23 is the hot-side of the circuit While wire 24 is grounded, as at 2'5. The control mechanism includes a suitable box or compartment 26 in which is positioned the terminal panel 21 and an electric motor driven timer switch unit which is designated in its entirety by the reference character 28. The top of the control box 26 has suitably mounted thereon an electric indicating lamp 29 which is enclosed within a suitable transparent globe or cover 39. 'Ihe indicator lamp 29 is intended to be energized at all times current is supplied to the control mechanism. Therefore, when the lamp is not burning, the attendant will know that the power is off or that the lamp has burned out. As the circuit for the indicator lamp 29 is the only one which is permanently closed, it will be traced first.

The hot supply Wire 23 extends to terminal 3I on the panel 21. From this terminal, the wire 32 extends to one terminal of the base of the lamp 29. The other terminal of this base is connected by the Wire 33 to one side of a resistor coil 34. Wire 35 extends from the coil 34 to the terminal 36 of a suitable manual switch 31 which includes the push button operator 38. This manual switch is normally conditioned so as to close the circuit to the fixed contact 39. Wire 40 extends from this contact 39 to terminal 4I on the panel 21. A wire 42 extends from terminal 4I to the grounded Wire 24 of the main supply Wires,

When operation of the fire extinguishing system is automatically initiated, one or more of the thermostatic switches 20 will function to close their rire detector circuit. The wires 43 and 44 of this circuit extend to terminals 45 and 46 respectively on the ter/minal panel 21. Terminal 45 is connected by wire 41 to one fixed contact 48 associated with the switch blade 49 that has its mounting post 50 connected by the wire 5I to the common hot wire 32 which was previously described as being connected to the hot-side 23 of the main supply Wires. The terminal 46 is connected by the wire 52 to the fixed contact 53 of the switch 54. The mounting post 55 of this switch is connected by the wire 56 to one terminal or side 51 of the synchronous motor 58. The other side or terminal 59 of this motor is connected to the previously referred to lamp circuit wire 40 that extends to terminal 4| of panel 21. This terminal 4| is connected to the grounded side 24 of the main supply wires by the wire 42. It will be seen, therefore, that closing of the circuit between the wires 43 and 44 by either one of the heat detecting, circuit closing switches 20 will bring about closing of the circuit to the timer motor 58.

This motor is provided with a shaft 6I) which carries suitable cams 6|, 62, 63 and 64. No attempt has been made to disclose any specific construction for these cam members but itis their function to actuate or move the previously referred to switch blades 49 and 54 as well as the two additional switch blades 65 and 66 into and out of engagement with normal or primary contacts and secondary contacts. The cam devices 6| to 64 inclusive, also, are intended to actuate their associated switch blades 49, 54, 65 and 66 in a predetermined timed sequence. For a more complete disclosure of an appropriate motor driven timer switch mechanism which may be employed as switch 28 of this control mechanism, reference may be made to the patent to Joseph H. Staley, No. 2,141,024.

The first function performed by the cam shaft 60 of the timer motor 58 is to disconnect the thermostatic switches 20 and their` circuit wires 43 and 44 from the motor circuit. To accomplish this desired result, cam 64 first operates to move switch blade 54 out of engagement with contact 53 and into engagement with contact 61. This contact 61 is connected by wire 68 to the common hot wire 32. The circuit for the synchronous motor 58 then is provided by the hot main wire 23, the hot common wire 32, wire 68 to switch terminal 61, switch blade 54 and Wire 56 to the terminal 51 of the motor, and wire 48 which is connected to the second terminal 59 of the motor and to terminal 4| of panel 21. This terminal 4| is connected to the grounded wire 24 of the main supply line by the wire 42.

The second function performed by the timer motor cam shaft 60 is to move switch blade 49 out of engagement with its contact 48 and into engagement with a second contact 69. This movement of switch blade 49 out of engagement with contact 48 disconnects the circuit wire 43 of the thermostatic switches from the common hot wire 32. Engagement of the switch blade 49 with its second contact 69 closes the circuit for the pre-discharge alarm 2|. This circuit includes the hot common wire 32, the wire 5| which leads to mounting post 50, the switch blade 49, switch contact 69, and wire 18 which leads to terminal 1I mounted on panel 21. This terminal 1| is connected to wire 12 that extends to one post of the pre-discharge alarm 2|. The second post of this alarm device is connected by the wire 13 to the grounded main supply wire 24. The pre-discharge alarm 2| should be permitted to operate for any desired time interval before the timer motor brings about a closing of the circuit to the carbon dioxide control valve I|.

Therefore, a predetermined time interval after cam 6| has actuated switch blade 49 to energize the pre-discharge alarm circuit, cam 62 will function to move switch blade 64 away from a dead contact into engagement with contact 14. Binding post 15 of the switch blade 65 is connected by wire 16 to the hot common wire 32. Contact 14 for the switch blade 65 is connected fby the wire 11 to terminal 18 on the panel 21. This terminal 18 has connected thereto the wire 19 which extends to one side of the electrical device for the carbon dioxide control valve The second side of this electrical control device is connected by wire to the grounded main supply wire 24.

Energizing the carbon dioxide control valve II causes carbon dioxide to flow through the pipe line 8. Some of this carbon dioxide flows through branch pipe I9 into the pressure operated switch I8. This switch functions to connect the grounded main supply wire 24 to wire 8| which-extends to one side of the electrical device for the petroleum control valve I5. The

-other side of this electric control device is conthat these valves I5 and |1 are connected in` parallel with each other and in series with the pressure switch I8. Terminal 83, of the panel 21, is connected by the Wire 86 to the terminal 81 associated with switch blade 66. The fourth function performed by the cam shaft 60 is to cause its cam 63 to move the switch blade 66 out of engagement with a dea-d contact and into engagement with the contact 81. The mounting post 88 for the switch blade 66 is connected to the common hot wire 32 by the wire 89.

The final function performed by the timer motor cam shaft is to move switch blades 54, 65 and 66 out of engagement with contacts 61, 14 and 81 respectively and back into engagement with their original contacts. The original contact for switch blade 54 bears number 53. The original contacts for switch blades 65 and 66 are dead or not connected to any circuit wires, and for that reason have not been given reference numerals.

The return movement of switch blade 54 breaks the motor circuit by disconnecting wire 56 from wire 68 which leads to the common hot wire 32. Movement of the switch blade 54 into engagement with contact 53 results in placing wire 44 of the re detecting, thermostatic switches 20 back in the motor circuit by connecting wire 52 with wire 56. Before reconnecting the second circuit wire 43 for the re detecting switches 2|) back into the motor circuit, it is necessary to first determine whether any of the switches 20 have been damaged by the fire in such a manner as provide a short circuit. Such a short circuit could be provided, for example, by freezing or fusing together the contacts of one of the switches 20. To test the circuit for switches 20, switch blade 31 is moved by its push button operator 38 into engagement with contact 88. This contact is connected by wire 9| to contact 48 which is associated with. switch blade 49. We then have a circuit from the common hot wire 32 through the indicator lamp 29 and its wires 33 and 35 to the mounting post 36 of switch blade 31 and from switch contact 90 through wires 9| and 41 to terminal 45 which is connected to wire 43 ofthe re' detecting switches 20. Circuit wire 44 of these me. mit tHNliUlSHERS,

switches 20 is connected by wire 52 to switch contact 53 and by switch blade 54 to wire 56 which leads to one terminal or side of the motor 58. The other side 59 of this motor is connected by wire 40 to terminal 4| which in turn is connected by wire 42 to the grounded main supply wire 24. If all of the fire detecting switches 20 are open, the indicator light 29 will not be ener- Sized. If either of the switches 20 is fused closed or is short circuited in any way, the indicator lamp 29 will be lighted and the timer motor 58 will be energized. If the re detecting circuit through switches 20 is open, push button 38 is released and its switch blade 31 will be returned to engagement with contact 39. If the fire detector circuit is open throughgthethmermostatic switches 20, the push button 92 may be used to move switch blade 49 out of engagement with contact 59, to break the circuit'to" the pre-discharge alarm device 2l, and into engagement with contact 48 for completing the connection of the fire detecting circuit wires 43 and 44 in series with the timer motor 58. 'Ilia/entire automatic contro l`mechanisn reset in condition for a subgt/Qperation to eect extinguishment of anothegnroccurring within the enclosed spaejlw Should it be desirable to initiate the operation of the fire extinguishing system manually, push button 93 may be employed for moving the switch blade 54 out of engagement with its contact 53 and into engagement with contact 61. It will be recalled that switch blade 54 was the first one that was actuated the cam shaft 60 and that movement of switch blade 54 into engagement with contact 61 caused the motor circuit to be closed after cutting out the circuit for the fire detecting switches 20.

It is to be understood that the form of this invention herewith shown and described is to be taken as a preferred example of the same, and that various changes may be made in the method steps and in the shape, size, and arrangement of parts of the apparatus without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:

1. A method of extinguishing a light metal fire burning in an enclosed space, comprising creating a moderate concentration of an inert gas in the said space, spramng a flammable liquid onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional inert gas into the space to create a iinal concentration which is suicient to prevent burning of the flammable liquid.

2. A method of extinguishing a light metal re burning in an enclosed space, comprising creating a moderate concentration of carbon dioxide vapor in the said space, spraying a flammable liquid onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional carbon dioxide vapor into the space to create a final concentration which is suflicient to prevent burning of the flammable liquid.

3. A method of extinguishing a light metal re burning in an enclosed space, comprising creating a moderate concentration of an inert gas in the said space, spraying a vegetable oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional inert gas into the space to createA a iinal concentration which is sufficient to prevent burning of the vegetable oil.

4. A method of extinguishing a light metal iire burning in an enclosed space, comprising creating a moderate concentration of carbon dioxide vapor in the said space, spraying a lubrication 'oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional carbon dioxide vapor into the space to create a iinal concentration which is suflicient to prevent burning of the lubrication oil.

5. A method of extinguishing a light metal re burning in an enclosed space, comprising releasing an inert gas into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, after a moderate concentration of said 4inert gas has been created in the space and while release of the gas is continued, spraying a liquid petroleum onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and continuing the release of the inert gas and the' spraying of the petroleum until the iire is extinguished.

6. A method of extinguishing a light metal iire burning in an enclosed space, comprising releasing carbon dioxide vapor into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, after a moderate concentration of said carbon dioxide vapor has been created in the space and while release of the vapor is continued, spraying a liquid petroleum onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and continuing the release of the carbon dioxide vapor and the spraying of the petroleum until the re is extinguished.

'7. A method of extinguishing a light metal iire burning in an enclosed space, comprising releasing an inert gas into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, `after a moderate concentration of said inert gas has been created in the space and while release of the gas is continued, spraying soy bean oil onto the burning metad to cover the exposed surfaces of the same with a smothering and cooling blanket, andvcontinuing the release of the inert gas and the spraying of the soy bean oil until the re is extinguished.

8. A method of extinguishing alight metal fire burning in an enclosed space, comprising releasing carbon dioxide vapor into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, after a moderate concentration of said carbon dioxide vapor has been created in the space and while release of the vapor is continued, spraying soy bean oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and continuing the release of the carbon dioxide vapor and the spraying of the soy bean oil until the iire is extinguished.

9. A method of extinguishing a light metal lire burning in an enclosed space, comprising creating a concentration of from 20 to 30 percent of an inert gas in the said space, spraying a fiammable liquid onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional inert gas into the space to create a gas concentration of approximately 50 percent which is 10. A method of extinguishing a light metal fire.'

burning in an enclosed space, comprising creating a concentration of from 20 to 30 percent of carbon dioxide vapor in the said space, spraying a lubrication oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and discharging additional carbon dioxide vapor into the space to create a gas cencentration of approximately 50 percent which is suincient to prevent burning of the lubrication oil.

11. A method of extinguishing a light metal fire burning in an enclosed space, comprising releasing an inert gas into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, after a concentration of from 20 to 30 percent of said inert gas has been created in the space and while release of the gas is continued, spraying soy bean oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and continuing the release of the inert gas and the spraying of the oil until a gas concentration of approximately 50 percent has been created.

12. A method of extinguishing a light metal re burning in an enclosed space, comprising releasing carbon dioxide vapor into the space in such a manner that it will avoid directly impinging against the burning metal and will not cause violent air turbulence, after a concentration of from 20 to 30 percent of the carbon dioxide vapor has been created in the space and While release of the vapor is continued, spraying a lubrication oil onto the burning metal to cover the exposed surfaces of the same with a smothering and cooling blanket, and continuing the release of the carbon dioxide vapor and the spraying of the lubrication oil until a vapor concentration of approximately 50 percent has been created.

13. A system for extinguishing a light metal re in an enclosed space, comprising means for discharging an inert gas into the space to create a lire extinguishing atmosphere, and means for spraying a flammable liquid onto the burning metal, during the discharge of the inert gas, to cover the exposed surfaces of the metal with a smothering and cooling blanket.

14. A system for extinguishing a light metal fire in an enclosed space, comprising means for discharging carbon dioxide vapor into the space to create a lire extinguishing atmosphere, and

means for spraying a flammable liquid onto the burning metal, during the discharge of the carbon dioxide vapor, to cover the exposed surfaces of the metal with a smothering and cooling blanket.

15. A system for extinguishing a light metal fire in an enclosed space, comprising means for discharging an inert gas into the space to create a re extinguishing atmosphere, and means for spraying a lubrication oil onto the burning metal, during the discharge of the inert gas, to cover the exposed surfaces of the metal with a smothering and cooling blanket.

16. A system fox` extinguishing a light metal re in an enclosed space, comprising means for discharging carbon dioxide vapor into the space to create a re extinguishing atmosphere, and means for spraying soy bean oil onto the burning metal, during the discharge of the carbon dioxide vapor, to cover the exposed surfaces of the metal with a smothering and cooling blanket.

17. A system for extinguishing a light metal lire in an enclosed space, comprising means, operating in response to automatic detection of the burning of the metal, for discharging an inert gas into the space for a predetermined time interval to create a lire extinguishing atmosphere, and means, operable after the inert gas has been discharged for a predetermined portion of its said time interval, for spraying a flammable liquid onto the burning metal to cover its exposed surfaces with a smothering and cooling blanket.

18. A system for extinguishing a light metal fire in anr enclosed space, comprising means, operating in response to automatic detection of the burning of the metal, for discharging carbon dioxide vapor into the space for a predetermined time interval to create a re extinguishing atmosphere, a source of supply of a flammable liquid, and means, operable after the carbon dioxide vapor has been discharged for a predetermined fractional portion of its said time interval, for applying carbon dioxide vapor pressure to the iiammable liquid in its source for effecting spraying of the liquid onto the burning metal to cause it to cover the exposed surfaces of the metal with a smothering and cooling blanket. l

19. A system for extinguishing a light metal lire in an enclosed space, comprising means, operating in response to automatic detection of the burning of the metal, for discharging an inert gas into the space for a predetermined time interval to create a fire extinguishing atmosphere, and means operable after the inert gas has been discharged for a predetermined fractional portion of its said time interval, for spraying a ammable oil onto the burning metal to cover its exposed surfaces with a smothering and cooling blanket.

20. A system for extinguishing a light metal lire in an enclosed space, comprising means, operating in response to automatic detection of the burning of the metal, for discharging carbon dioxide vapor into the space for a predetermined time interval to create a fire extinguishing atmosphere, and means, operable after the carbon dioxide vapor has been discharged for a predetermined fractional portion of its said time interval, for spraying a lubrication oil onto the burning metal to cover its exposed surfaces with a smothering and cooling blanket.

CHARLES A. GETZ.

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