What are some reasons why faber feels "alive for the first time in years"?

Faber feels alive because Montag's actions have finally given him the courage to act on his beliefs..... to participate rather than merely observe.

"I feel alive for the first time in years," said Faber. "I feel I'm doing what I should have done a lifetime ago. For a little while I'm not afraid. Maybe it's because I'm doing the right thing at last. Maybe it's because I've done a rash thing and don't want to look the coward to you. I suppose I'll have to do even more violent things, exposing myself so I won't fall down on the job and turn scared again. What are your plans?"