This of course happens in the third section of this great dystopian novel, when Montag is confronted with his crimes of book reading by Beatty and, as punishment, is made to burn his own house. What is interesting about this however is the apparent joy in which Montag does this. When he starts burning, the old attraction to fire rises within him once again. Note how this scene is described in the text:
He burnt the bedroom walls and the cosmetics chest because he watned to change everything, the chairs, the tables, and in the dining room the silverware and plastic dishes, everything that showed that he had lived here in this empty house with a strange woman who would forgethim tomorrow, who had gone and quite forgotten him already, listening to her Seashell Radio pour in on her and in on her as she rode across town, alone. And as before, it was good to burn, he felt himself gush out in the fire, snatch, rend, rip in half with flame, and put away the senseless problem.
The way in which fire is described as a force that purifies and cleanses is thus immensely attractive to Montag. Having identified the emptiness and barren nature of his own life, to finally symbolically burn it represents an ending of that life and its meaninglesness. In addition, burning seems to allow him to "put away" the various doubts and troubles that have been plaguing him. Montag thus responds very positively to burning up his house. Perhaps we can relate this to somebody whose secret is finally out and the relief that they often experience.