Oxygen does NOT burn without fuel.
Contrary to common misconceptions, oxygen is surprisingly not flammable in itself. That being said, oxygen is necessary for fires to occur. This is due to its nature as the strongest, most common oxidizer.
Background on the Element
Oxygen is found naturally as a gas and makes up 21% of our atmosphere by volume. Due to the number of valence electrons the chemical possesses, oxygen is most commonly found paired to another atom of oxygen. Making its common atomic allotrope O2, or dioxygen. [“The Rise of Oxygen.” Astrobiology Magazine]
Oxygen as an Oxidizer
We get the term oxidizer from the name oxygen. This is due to the fact that oxygen was the most common reactant with the truly flammable fuel. Chemically, oxidization is the name given to any process that results in the loss of electrons. It’s this activity in the electron cloud that causes the flames in the first place. [“Oxidizing and Reducing Agents” University of California Davis]
Active flames require two things: fuel and an oxidizer. The fuel is often some derivative of carbon but can be a host of other elements as well. The oxidizer is oxygen. Since oxygen coupled with oxygen does not create a burn, it stands to reason that it can’t also double as a flammable fuel. In other words, nothing can oxidize oxygen because it is the strongest natural oxidizing agent. [“Flammability and Oxygen ” NEWTON]
Oxygen in Combustion
Combustion is the process that the oxidizing agent and the fuel take in creating chemical reactions. But, again, it isn’t the oxygen itself that is flammable. It is the fuel that literally feeds the flame. Oxygen is the agent that allows it to exist. Oxygen is chemically changed during combustion, however. Oftentimes its chemically bonded to whatever fuel was used and found in the resulting surrounding atmosphere. This is why fossil fuels release so much CO2 from combustion. The compound is a result from the combustion of the carbon heavy fuel. [“Oxygen and Combustion .” NEWTON]
“The Rise of Oxygen.” Astrobiology Magazine — The Origin and Evolution of Life in the Universe . N.p., n.d. Web. 8 Jan. 2013. <http://www.astrobio.net/exclusive/541/the-rise-of-oxygen>.
“Oxidizing and Reducing Agents.” University of California Davis: ChemWiki: The Dynamic Chemistry Textbook – ChemWiki. N.p., n.d. Web. 8 Jan. 2013. http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Redox_Chemistry/Oxidizing_and_Reducing_Agents
“Flammability and Oxygen .” NEWTON, Ask a Scientist at Argonne National Labs!. N.p., n.d. Web. 2 Jan. 2013. http://www.newton.dep.anl.gov/askasci/chem03/chem03291.htm
“Oxygen and Combustion .” NEWTON, Ask a Scientist at Argonne National Labs!. N.p., n.d. Web. 2 Jan. 2013. http://www.newton.dep.anl.gov/askasci/chem00/chem00325.htm