The words are taken from Isaiah 34:10. It is a passage in which Isaiah handles the judgment of Edom, yet it is applied here to Babylon.
She is destroyed, but the smoke never abates. In other words, there are some things in eternity, in glory, that the redeemed will always remember. They will always have some memory of the Day of Judgement. Not a sad memory – there is only untainted happiness and glory in heaven – but a sobering memory. You couldn't say, for example, that in a million years-time, amidst the wonders and the glories of heaven, we will have forgotten what redemption was all about, so that we might wonder, in our great liberty of mind, ‘What would it be like without God? Would it be so bad? We would forget the episode of planet earth, and the rebellion of man, and his antagonism to God?’ No, the smoke will rise for ever. There will be, in some form, a sobering recollection of the tragedy of mankind's ever turning away from God.