nitrous gases in exhaust gases represent pollutants that are not only detrimental to the environment but are also a health hazard . nitrous gases are generally a mixture of no and no 2 . the nitrous gases can be reliably removed from the exhaust gases by means of a solution containing ammonium salts . for this purpose , the exhaust gas with the nitrous gases is passed through the solution wherein the scrubbing process occurs in accordance with the following equation : as a reaction product of this scrubbing process nitrogen is thus produced . because the comproportionation is carried out in the acidic range , additional acid is produced according to the equation . however , no other waste products are produced that would have to be disposed of . the scrubbing process can be carried out in conventional contact apparatus that are used for gas scrubbing . examples of such contact apparatus are scrubbing columns with packed bed or fixed packing , bubble columns and the like . fig1 shows in an exemplary fashion such a scrubber with a container 1 in which the scrubbing liquid 2 is contained . at least one conduit 3 through which the exhaust gas 4 containing the nitrous gases are supplied opens into the container 1 . the conduit 3 extends to the bottom 5 of the container 1 . the conduit 3 extends advantageously at minimal spacing along the inner side of the wall 6 of the container and has a distribution nozzle 7 arranged approximately centrally relative to the bottom 5 from which nozzle the exhaust gas to be cleaned exits upwardly into the scrubbing liquid 2 . the nitrous gases contained in the exhaust gas 4 are absorbed in accordance with the above described equation in the scrubbing liquid 2 and are converted by the reaction according to above mentioned equation to nitrogen . the cleaned exhaust gas flows through at least one outlet conduit 8 to the exterior which conduit is arranged above the scrubbing liquid level near the upper edge of the container 1 . the scrubbing liquid 2 is comprised of water in which ammonium salts , for example , ammonium sulfate or ammonium hydrogen sulfate , are dissolved . it is also possible to dissolve ammonia in water . per kilogram of no 2 gas 0 . 4 kg of ammonia is required . when ammonium hydrogen sulfate nh 4 hso 4 is used , 3 . 34 kg of nh 4 hso 4 in 40 liters of water are used per 1 kg of no 2 . with such a scrubbing liquid at least 100 m 3 of exhaust gas with nitrous gases no x in a concentration of 8 , 000 mg / m 3 can be cleaned . depending on the concentration of the nitrous gases in the gas 4 , the aforementioned scrubbing solution quantity also suffices for cleaning larger volumes . for example , for a concentration of 800 mg / m 3 1 , 000 m 3 exhaust gas can be cleaned . when the replacement of scrubbing liquid is carried out continuously , for an exhaust gas flow rate of e . g . 5 , 000 m 3 / h at a concentration of 800 mg / m 3 it is necessary to supply 13 . 4 kg nahso 4 in 160 liters of water and the equivalent amount of wastewater must be removed . when the concentrations of nitrous gases in the exhaust gas 4 are higher , a larger quantity of scrubbing liquid and a corresponding addition of ammonium salts are needed . in a typical case , for 3 , 000 m 3 / h exhaust gas that contains 10 kg no 2 / h as nitrous gas , 33 kg / h nh 4 hso 4 in 400 i / h water would be required . metering of the gaseous or liquid ammonia or ammonium salt is carried out advantageously by measuring the no 2 concentration in the cleaned exhaust gas flowing out through outlet conduit 8 . when the concentration in the cleaned exhaust gas surpasses a permissible or preset value , ammonium salt solution or ammonia gas is added . this is done advantageously automatically so that a continuous cleaning of the exhaust gases is possible without problem . fig2 shows the possibility of adding ammonia gas 9 to the exhaust gas 4 before the exhaust gas enters the scrubbing solution 2 . the ammonia gas 9 is supplied by conduit 10 that opens into the exhaust gas conduit 3 . such an embodiment is advantageous when , for example , the ammonia gas is an additional exhaust gas that is produced in the same factory as the exhaust gas 4 containing nitrous gases . it is then possible in this factory to employ the exhaust gas in the form of ammonia gas for removing the nitrous gases from the exhaust gas 4 . the described scrubbing liquid 2 is often produced in large factories as waste solution . as a result of its secondary use as a scrubbing solution , the scrubbing solution provides an inexpensive alternative to the conventional cleaning processes . the described scrubbing process for removing the nitrous gases from exhaust gases is advantageously utilized in the production of solar cells , in particular , photovoltaic cells . in such solar cell factories usually 50 to 80 % reduction of the no x emissions is required . these reductions can be realized reliably with the described method . in comparisons to neutralization scrubbers the described method is significantly more powerful and more effective . in order for the nitrous gases to be removed reliably from the exhaust gases 4 , in the container 1 a sufficient liquid volume is present . the exhaust gas 4 to be cleaned is introduced at such a pressure and thus at such a speed into the scrubbing liquid 2 that a gas residence time sufficient for removal of the nitrous gases is ensured . this ensures that no contained in the exhaust gas is oxidized to no 2 : this reaction occurs spontaneously in the gas phase and must not be initiated in a special way . the scrubbing process can be carried out in a temperature range of approximately 5 ° c . to approximately 40 ° c . at higher temperatures the cleaning of the exhaust gases is more effective than at lower temperatures . advantageously , the scrubbing liquid 2 circulates during the scrubbing process in order to achieve an optimal cleaning action of the exhaust gas 4 . for effecting circulation , the scrubbing liquid 2 is introduced at a pressure of up to approximately 3 bar into the container 1 . the concentration of ammonium salts can be up to approximately 5 mol % nh 4 + / i solution . the exhaust gas to be cleaned can have a temperature of approximately 0 ° c . to approximately 200 ° c . in this connection , the exhaust gas can be introduced at a pressure of up to approximately 3 bar into the scrubbing liquid 2 . the exhaust gas 4 can contain up to approximately 1 , 000 mg / m 3 no x gas . the water utilized for the scrubbing liquid 2 is advantageously neutral . as a result of the cleaning process , the liquid becomes acidic , i . e ., the ph value drops below 7 . as a result of the reaction of ammonium salts with the nitrous gases in the exhaust gas 4 acids are formed that cause the ph value of the water to drop . a neutralization is not required for maintaining the scrubbing function . it has been found that per kg of no 2 approximately 0 . 4 kg ammonia are required . the scrubbing liquid utilized for cleaning the exhaust gases 4 is inexpensive , in particular , because it is present as a waste solution depending on the type of industrial facility . the employed scrubbing apparatus can be of a simple construction . the described method is also very well suited for cleaning relatively small volumes of air . such minimal exhaust gas quantities occur , for example , in the case of wet benches for etching silicon . the method can be utilized excellently for such applications . when using ( nh 4 ) 2 so 4 solutions , the cleaning activity will increase at ph neutral and with increasing cleaning duration . this is inter alia the result of the scrubbing liquid 2 becoming increasingly acidic with increasing cleaning duration because the no 2 produced in the cleaning process causes a shift of the ph value to lower values . in the acidic range , the reaction rate of the scrubbing process will increase . because for the scrubbing process a satisfactory liquid volume must be present , as a scrubbing device advantageously an apparatus of the type of a bubble column is used . such apparatus are known and will therefore not be explained in more detail with regard to their construction . it is also possible to employ an air washer with packing material , a so - called scrubber , as a scrubbing device . such air washers are characterized by their small size so that they can be utilized advantageously where large exhaust gas volumes are to be expected . the use of ammonium sulfate has the advantage that it is inexpensive and can be purchased cheaper than h 2 o 2 that has been used up to now . a further advantage of using ammonium sulfate resides in that it is produced as wastewater of ammonium scrubbers and can be utilized as a scrubbing liquid for removing nitrous gases from exhaust gases .