Historically, physicists created a graphical representation detailing the three elements of fire (fire triangle). In recent years, one more point has been added, ＿＿（51）＿＿ the fire tetrahedron. The four elements needed to ＿＿（52）＿＿ combustion are: fuel, oxygen, heat and a chemical chain reaction. To extinguish a fire, it is ＿＿（53）＿＿ to remove one or more of the four components of combustion. Removing any of these components of the fire tetrahedron will stop the other elements from interacting and not allow combustion to ＿＿（54）＿＿ . Firefighters work on limiting ＿＿（55）＿＿ (fuel that is in jeopardy of being ignited by nearby flame or from radiant heat), containing and extinguishing fire and then overhauling charred and burned debris from the affected areas as well as extinguishing all hidden fires to prevent a rekindle.