How does Montag defeat the mechanical hound?

Montag defeated the mechanical hound with the flame-thrower.

He felt it scrabble and seize his leg and stab the needle in for a moment before the fire snapped the Hound up in the air, burst its metal bones at the joints, and blew out its interior in the single flushing of red colour like a skyrocket fastened to the street. Montag lay watching the dead-alive thing fiddle the air and die.