how was the use of fire in Fahrenheit 451 significant to the whole plot?

Beginning with the 'The Hearth and the Salamander', the novel alludes to images of fire, the tool of destruction that censors knowledge and ideas. The hearth is where the fire is built and burns strongest. In contrast, the salamander is a lizard said to survive in flames, and thus alludes to fire's inability to crush free thought. Montag, personifies the salamander, surrounded in flames, yet fighting against censorship. Fire represents purification as it is used to rid society of that which is undesirable. Books and the places where they are hidden are eradicated by fire, burned out of existence so as not to contaminate society. In his long discussion with Montag, Captain Beatty mentions the standard practice of immediately cremating the dead so society is not burdened with decaying bodies or memorials and the grief associated with them. Later, as Montag comes to realize the truth about his society, he recognizes fire as a form of oppression - a means of subduing the knowledge in books. Fire also represents awareness and memory. Upon greeting the firemen, the old woman who later burns to death among her books as a martyr for free thought, quotes Bishop Hugh Latimer, who was burned for heresy in the 16th century, saying, " . . . we shall this day light such a candle, by God's grace, in England, as I trust shall never be put out!" This quote rings true with Montag, who later laments, "you ever see a burnt house? It smolders for days. Well, this fire'll last me the rest of my life." Fire is also important for its transformative powers. In the opening paragraph of the novel, the author refers to the pleasure Montag took in seeing things changed by fire. Similarly, Montag changes with each fire he sets.