The use of cooker-hoods in homes is widely spread world wide. Most manufacturers continuously increase the absorbent force of air extractors. They continuously use stronger fans to allocate bigger absorbent forces (using more electricity), trying to justify that "the absorbent force is not sufficient". The reasons are not notified to the consumers and the consumers are not interested to learn details; however they are seeking to buy products that will give those solutions to their remaining problem. On the contrary the "complaints" are increased by consumers that this increased force does not produce the expected results. The complaints are: "unbelievably sewage gases still remain in my kitchen " , "water vapors still remain in my kitchen ", "when I am cooking, the smoke from the fireplace fills the house". In our opinion the "unbelievably" is a certainty. Today, we are materializing doors and windows by aluminum or PVC. These materials are sealing the gaps of the house and isolate the house from the exterior environment. They are in fact promoting heat insulation and sound proofing of the house but they incriminate the cooker-hood. The appearance of mildew at the walls and the deliquescence of water vapors on the windows during winter indicate that the cooker-hoods are operating insufficiently. Therefore in order for the cooker-hood to work properly, a window or a door is required to be half opened. As a result there is losing of heat during the winter and cold air in the summer. Obviously there is a failure of domestic cooker-hoods and the serious disadvantage is that, big air sub pressure is created into the sealed house's shell and does not allow the absorption of sewage gases and consequently their export from the interior because the absorbent force of cooker-hood fans equilibrate the difference between internal created air sub pressure and the exterior pressure. Thus, the fins of the export fan try with their rotation to export the sewage gases outside the house, but substantially after the equipoise, they are continually cutting the same air mass, and create the final result, "while cooking, all the created sewage gases and the water vapors remain in the interior". If a window or a door is opened for a short time, the export fan undertakes to return to the previous pressure balance, by extracting some of the sewage gases to the exterior. It is only at that time the function of cooker-hood is correct.

According to the implementation of the present invention, the possibility is given to import the necessary clean fresh air in the house's interior, as a compensation of the outgoing volume of the sewage gases, through the structure of the cooker-hood. It is achieved with one import air-duct for the clean fresh air, which encloses the classic air-duct of the outgoing sewage gases (coaxial system of two air-ducts) as proposed in the present invention. The proposed material of export air-duct (for sewage gases) is metal. The import air-duct (for clean fresh air) could be from plastic or metal. The import air-duct encloses the export air-duct, in order to, firstly to give the possibility of balance the external pressure and the internal pressure, with the import of clean fresh air, thus preventing the creation of air sub pressure in the house, secondly the export volume of sewage gases, to warm-up the import air through the metallic material of the export air-duct which is between the import and the export air masses and thirdly, there is no need to modify the diameters of the air-ducts which are already in use. The diameter of the export air-duct is proposed to the standard to date dimension, so the system of the two coaxial air-ducts can be also installed in already existing installations without any modifications. The importing clean fresh air: a) it is diffused in the air mass of the cooker room, around and above the cooker-hood through orifices adapted at any point of the import air-duct, or b) It creates an air curtain with at least a fan, as proposed in the present invention. The air curtain created in the space between the cooker hood and the hearth blocks the mixing of the air mass above the hearth, with the air mass of the kitchen and the house's interior. The incoming clean fresh air is preheated (specifically for the winter) a) Passively, through the coaxial pipes. The metallic export air-duct is between the warm sewage gases and the incoming colder clean fresh air (it works like a heat exchanger) and b) Optionally by the will of the consumer, via electric radiators. The air temp is regulated by the will of the consumer, automatically or manually. Because, with this way the import air mass is equal with the export air mass, therefore the house pressure is equal with external pressure, therefore acted the sub pressure's interception, finally this system does not need a high force for the export fans. With reference to the air curtain now, at least one extra fan is still required, because the air curtain must be created with the import air. The air mass above the hearth is environed by the air curtain. The air curtain has the form of an adjacent surface of a truncated cone square pyramid. This air pyramid has a wide square base with slightly larger dimensions of the hearth, has a smaller upper square base with the same dimensions as the bottom of the cooker-hood. Its height is the distance between the hearth and the bottom surface of the cooker-hood. Thus the sewage gases now are created inside the air curtain. The export fan absorbs the contents that are produced inside the air curtain, and the most part of the air curtain, specifically from the lower section of the air curtain. The lower part of the air curtain is bent inwards, assisting the export of sewage gases since the bent of the air curtain to the interior has the tendency to assemble the sewage gases in the middle of the hearth and from there in their export. Thus, the main objective of the present invention is all volume of sewage gases that is created and all volume of air that enters from the pipe of import, to be the total volume of gases that comes out leaving the volume of air in the house intact, hence in his regular pressure avoiding completely the air sub pressure in the house's interior. Generalizing we can say that the advantages of the present invention are obvious for suppressing the air sub pressure and that the present invention has an easy implementation in each air-conditioned building which disposes a new or old ventilating system and materializes its ventilating system with air extractors.

The present invention can be completely comprehended from the following analytic description concerning the attached figures 1,2,3,4 and 5. Figure 1 shows a vertical section of a typical cooker-hood, with modified operation. In this figure is included: a) the import air-duct of clean fresh air b) the export air-duct of sewage gases c) the gap between the cooker-hood's outer shell and the special partition as proposed in the present invention d) the fans for the creation of the air curtain e) the electric radiators which the import air is preheated, optionally by the will of the consumer. In the same figure are shown the air curtain's orifices and the air curtain above the hearth (spotty arrows). Figure 2 shows a part of the export air-duct and a part of the import air-duct respectively in the house interior. The import metallic or plastic air-duct encloses the export metallic air-duct. It also shows the course of the air masses through air-ducts (with spotty arrows). Figure 3 shows a proposal for the air-duct's orifices exits at the house's exterior, so that the exported sewage gases and the imported clean fresh air are not mixed with each other (creation of the distance between the import orifice and export orifice). Figure 4 shows a typical electric cooker with its hotplates and a heated saucepan. Figure 5 shows with the help of spotty arrows the air curtain and the course of the gas masses above the hearth, according to the present invention.

In order to help the reader, identical report numbers are used in the text and the Figures 1-5, and also for the characterization of the common elements of the Figures.

In the Figure 1 appears a vertical section of a typical as to the form but also as proposed to the operation of the cooker-hood, where (1) is its outer shell and (2) the internal partition with the gap as proposed in the present invention, which abut to the cooker-hood's orifices (3), via which preheated clean fresh air (18), (17), abuts in the kitchen's interior, and create an air curtain (4). The air curtain has the form of an adjacent surface of a truncated cone square pyramid. This air pyramid has a wide square base with slightly larger dimensions of the hearth, has a smaller upper square base with the same dimensions as the bottom of the cooker- hood. Its height is the distance between the hearth and the bottom surface of the cooker-hood. The lower part of the air curtain is bent inwards (15), assisting the export of sewage gases since the bent of the air curtain to the interior has the tendency to assemble the sewage gases in the middle of the hearth and from there in their export via export fan(5). The export fan (5) of sewage gases, is adapted in the partition (2), is sealed in regard to the gap between the outer shell of the cooker-hood (1) and the internal partition (2). It has the possibility to drive (16) the sewage gases via the typical filter (6), into the export air-duct (7) and from there on (16), to the exterior of the house (Figure 3). The outer shell of the cooker- hood (1) is connected with a metallic or plastic air-duct which imports clean fresh air (8). This air-duct (8) has a bigger diameter than that of the export air-duct of sewage gases (7) (coaxial air-ducts). In the gap between the outer shell of the cooker-hood (1) and the partition (2) there are one or more fans (9), which have been installed there and absorb the clean fresh air (17) via the import air-duct (8). Clean fresh air, is optionally preheated (18) via the electric radiators (10) at the will of the consumer and the temp is regulated by the will of the consumer, automatically or manually. The clean fresh air is abutting to the narrow size of the orifices (3) and the air current develops high speed creating the air curtain (4).

In Figure 2 we can see the export air-duct of the sewage gases (7) (metallic) and the import air-duct of the clean fresh air (8) (metallic or plastic), as they are connected with the cooker- hood of Figure 1 in the kitchen's interior. The proposed diameters are 8 0 (7) and 12 0 (8), ensuring that the active cross-section of the export air-duct flow is roughly equal with the active cross-section of the import air-duct flow.

In Figure 3 we can see a proposal for the air-duct's orifices exits at the house's exterior, so that the exported sewage gases (16) and the imported clean fresh air (17) are not mixed with each other. (Creation of the distance between the import orifice and export orifice)

In Figure 4 we can see a typical electric cooker with its hotplates (11) and a heated saucepan (12) in operation for the needs of the present description and for the convenience of the reader to comprehend the present invention. Water vapors and other sewage gases (13) are produced above the saucepan. In Figure 5 we can see the course of the gas masses above the hotplates (11) of electric cooker, above the saucepan (12) as well under the cooker-hood. The air curtain (4) is created by the impulse of the fans (9) and it follows the course of the spotty arrows (4). We wish to remind to the reader that, the clean fresh air of the air curtains (17) which potentially is preheated (18) from the electric radiators (10), abuts via the perimetric orifices (3) in the lower part of the cooker-hood. The lower part of the air curtain is bent inwards (15) because of the air sub pressure in the interior of the air curtain. The air sub pressure is created because of the absorption of gas masses from the export fan's (5) operation in the centre of the gas volume above the hearth (14) in the interior of the air curtain (4), (15). The air curtain's air masses (15) drift the sewage gases (13). The mixed air masses follow the route in the middle (14) and are exported via the export fan (5). Thus air masses from the air curtain's lower part (15) are assembled and are mixed with sewage gases (13) in the air curtain's center (14), are passed through the export fan (5) via the export air-duct (7) and they abut to the outside of the house.

The objective of the present invention is for suppressing air sub pressure created in home's interior by domestic cooker hoods. Therefore the absorbent force of import fans (9) must be equal or a bit smaller than the absorbent force of the export fan (5) thus avoids the creation of internal sub pressure, ensures that the exterior air pressure is equal to the interior air pressure and the cooker hood's operation produces desirable results.