In Fahrenheit 451 how does Faber define the job of a firemen?

what they do is that they detect hidden and illegal books in people's houses and then they burn the books and the houses that conceal them. They do this for a living because it is the complete opposite of what firemen do now. Today, firemen put out fires instead of starting them, but in this society of F.451, every house is fire proof so there really isn't a need to have firefighters or people to put out fires. Then as controversy and conflict start to arise from the issue of books, the government decides to give firemen the job of burning books instead so that is why they do what they do for a living.