Process for producing dinitrotoluene, comprising the steps of: a) nitration of toluene with a mixture of nitric acid and sulfuric acid with subsequent separation of a sulfuric-acid-containing aqueous phase formed during the nitration to obtain a crude dinitrotoluene, b) washing the crude dinitrotoluene in a water wash with neutral and/or alkaline washing water, wherein after separation of the washing water employed in the last wash a prepurified dinitrotoluene is obtained which comprises besides dinitrotoluene also at least water and c) separating the water from the prepurified dinitrotoluene, d) collecting the wastewaters from steps a), b) and/or c), e) optional extraction of the collected wastewaters from step d) with toluene and recycling of the thus obtained organic phase into step a), f) freeing the collected wastewaters from step d) or, if optional step e) is performed, the extracted wastewater from step e) of toluene in a toluene stripper to obtain a toluene-containing offgas stream, g) supplying the offgas stream from step f) into an offgas condenser and removing the toluene present in the offgas stream in this offgas condenser, wherein all offgas streams from steps a), b) and c) and also optionally d) and optionally e) are combined and fed either into the offgas stream that is to be supplied to the offgas condenser or into the offgas stream leaving the offgas condenser, characterized in that the process comprises the further step of: h) supplying the offgas stream generated in step g) after the condensing-out of the toluene to a thermal exhaust air purification, wherein nitrogen is added to the offgas stream to be supplied to the offgas condenser or to the offgas stream leaving the offgas condenser, wherein preferably a nitrogen concentration in the offgas stream of at least 0.1 vol% is established, particularly preferably of at least 0.5 vol%. a) nitration of toluene with a mixture of nitric acid and sulfuric acid with subsequent separation of a sulfuric-acid-containing aqueous phase formed during the nitration to obtain a crude dinitrotoluene, b) washing the crude dinitrotoluene in a water wash with neutral and/or alkaline washing water, wherein after separation of the washing water employed in the last wash a prepurified dinitrotoluene is obtained which comprises besides dinitrotoluene also at least water and c) separating the water from the prepurified dinitrotoluene, d) collecting the wastewaters from steps a), b) and/or c), e) optional extraction of the collected wastewaters from step d) with toluene and recycling of the thus obtained organic phase into step a), f) freeing the collected wastewaters from step d) or, if optional step e) is performed, the extracted wastewater from step e) of toluene in a toluene stripper to obtain a toluene-containing offgas stream, g) supplying the offgas stream from step f) into an offgas condenser and removing the toluene present in the offgas stream in this offgas condenser, wherein all offgas streams from steps a), b) and c) and also optionally d) and optionally e) are combined and fed either into the offgas stream that is to be supplied to the offgas condenser or into the offgas stream leaving the offgas condenser, <EOS>