Why do you think Montag vomits?Why does Montag want to skip work?
Montag has begun to realize what their society has become. Clarisse started him thinking when she asked him if he was happy. Then when he witnessed the woman who burned herself with her books rather than give up her books, the realization of what he and everyone else has allowed their world to become sickens Montag. He is shaken to the core by this new knowledge and this is what makes him vomit and this is what makes him decide to stay home from work. Beatty has picked up on this feeling from Montag and that's why he comes to visit Montag at Montag's house. Montag knows that he has been part of the problem by simply being a fireman and burning books. Mildred is also part of the problem with her love of her TV and her TV "family" as well as her empty-headed friends. When Montag witnesses the woman who would rather die a horrible death than live in the society in which Montag, Mildred, and all the others live, he sees how empty and awful their society is.