During his conversation, Montag says that "You never wash it off completely" referring to the kerosene. What could this mean symbolically?

The kerosene represents all the knowledge, lives, homes, and books he has destroyed. Montag can never wash away what he has done. Like the stench of the kerosene, Montag’s deeds linger in his mind and soul. 

What does Montag smell of? Why does he smell like this?