This essay argues that the literary atmosphere of Charles Dickens’s Little Dorrit (1855–57) reciprocates the condition of the mid-century London air, as Dickens understood it. Through exploring the novel’s connections with contemporary medical-political debates about air purity, I hope to show that the novel can be read as a study of atmospheric influence, in both material and moral terms. In particular, I examine the metaphorical and phenomenal roles of airborne pollutants in the narrative. Dickens repeatedly correlates socioeconomic with meteorological climates: toxic investment spreads like an epidemic miasma; shady business dealings leave murky deposits; debtors are trapped in conditions of bodily and psychological stagnancy. Eventually these clouds lift from the imprisoned Clennam: as forms of atmospheric contamination the Marshalsea’s imprisoned air, the tainted ambience of the Clennam house are purified or dispersed. In Little Dorrit air becomes a medium of interchange between the body and its environment, between individuals and their society, and between the literal and the figurative.