Roses and Mustard Gas

In the final chapter of Slaughterhouse-Five, Kurt Vonnegut re-introduces himself into the story. He returns to speaking in first person of the situations that happened to him and Billy Pilgrim. On page 214, Vonnegut makes a personal observation of what it was like in the "corpse mines" of Dresden. He gives the reader the image of, "There were hundreds of corpse mines operating by and by. They didn't smell bad at first, were wax museums. But then the bodies rotted and liquefied, and the stink was like roses and mustard gas."
Yuck. Roses and mustard gas? I've heard that before, from the first chapter to describe alcoholic breath. Vonnegut is directly referencing the first chapter here, and he is also giving the reader a direct image appealing to the reader's sense of scents, smell. Vonnegut uses this image to describe that the smell of the rotting corpses is the worst smell he can think of, so he associates the smell with alcoholism and roses and mustard gas, which must not be Vonnegut's two favorite stenches. Whenever Vonnegut describes a rotten odor, he always refers to the stench as "roses and mustard gas." He clearly must hate the scents.
In addition, the quote above also is more than an image; it is a dramatic understatement. An understatement is a severe type of verbal irony where the author says much less than what is meant. When Vonnegut says, "They didn't smell bad at first... the stink was like roses and mustard gas", he is understating just how rotten the smell actually was. Dead bodies are clearly much stinkier than roses and mustard gas, but, again, Vonnegut simply used those two smells to reference chapter one.The reader knows Vonnegut wasn't serious when he said they didn't smell bad at first. Of course they did! We're talking dead bodies here. Gross.
To conclude, I'm going to provide a video from Spongebob, because whenever something smells bad, I always quote Mr Krabs from the very first episode. Surely, whenever Vonnegut smells something he doesn't like, he must always compare the stench to roses and mustard gas, but I always use this quote from Mr Krabs: