During Montag's run from the law in Fahrenheit 451, how are light and dark used ironically?

The dichotomy between light and dark is a motif that is used fairly consistently throughout Fahrenheit 451. Light is symbolically paired with fire, and Montag frequently associates it, particularly at the beginning of the story, with fond memories and interactions. He finds a particular comfort in the light of candles, and even compares the warmth of Clarisse's face to that of candlelight. At the end of the story, this dichotomy becomes ironic because, as Montag flees from the mechanical hound, the significance of these symbols becomes completely reversed. In this situation, light becomes a sign of sure capture and death, and Montag must avoid it at all costs. Montag knows that his pursuers are consequence oriented, being only concerned with making it seem as though he has been killed. He realizes that if he can just escape far enough into the obscuring darkness, he will be able to survive the ordeal. In this sense, darkness has ironically become Montag's salvation and existential light.