Fahrenheit 451 is the temperature at which books burn. In order to destroy them completely, the firemen spray kerosene on them to accelerate the fire. It allows them to burn hot and turn to ash. It is the fire department's job to find and burn books. By using gasoline, the books are forever destroyed and cannot be recovered for any knowledge. By completely burning them, they are "out of the sight and mind" of society. Therefore, according to the government, people are happier and lack the intelligence and knowledge of philosophy, history, science, and literature of the past. All knowledge is wiped out, and the people don't have to worry their little minds about things like religion, history, or the war waging around them. They are free to be content to watch soap operas on wall size televisions.