Without the presence of oxygen, combustion cannot occur as it is the oxygen in the air that enables the chemical reaction of fire. The process of combustion involves the rapid oxidation of a fuel source in the presence of oxygen, releasing heat, light, and various combustion products.
In an oxygen-deprived environment, such as a closed system or a fire with limited oxygen supply, the fire will eventually extinguish. Without oxygen, the fuel source cannot sustain the necessary chemical reactions to continue burning. Consequently, the temperature will decrease as the fire dies out.
However, it's worth noting that certain materials can undergo self-sustaining reactions even without atmospheric oxygen. For example, certain chemicals can decompose or react exothermically in the absence of air or oxygen, generating heat. These reactions are different from traditional fire combustion, as they don't require continuous oxygen supply and operate on different principles. The temperatures reached in such reactions would depend on the specific materials involved and their reaction kinetics, but they are generally lower than the temperatures achievable in a typical fire fueled by oxygen.