<P> To stop a combustion reaction, one of the three elements of the fire - triangle has to be removed . </P> <P> Without sufficient heat, a fire cannot begin, and it cannot continue . Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction . This is often water, which absorbs heat for phase change from water to steam . Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for the fire reaction in the same manner . Scraping embers from a burning structure also removes the heat source . Turning off the electricity in an electrical fire removes the ignition source . </P> <P> Without fuel, a fire will stop . Fuel can be removed naturally, as where the fire has consumed all the burnable fuel, or manually, by mechanically or chemically removing the fuel from the fire . Fuel separation is an important factor in wildland fire suppression, and is the basis for most major tactics, such as controlled burns . The fire stops because a lower concentration of fuel vapor in the flame leads to a decrease in energy release and a lower temperature . Removing the fuel thereby decreases the heat . </P> <P> Without sufficient oxygen, a fire cannot begin, and it cannot continue . With a decreased oxygen concentration, the combustion process slows . Oxygen can be denied to a fire using a carbon dioxide fire extinguisher, a fire blanket or water . </P>

Which of the following is not a part of the fire triangle