The Question and Answer section for Fahrenheit 451 is a great resource to ask questions, find answers, and discuss the novel.
From the text:
"And in her ears the little Seashells, the timble radios tamped tight, and an electronic ocean of sound .."
People are afraid of firefighters becasue they're afraid of losing their homes and their lives.... particularly if they are harboring books in their homes.
The novel is set in the future.... looking back at books, television shows, and the way the written word has changed up until that time.