What is a potential effect of an oxygen-deficient atmosphere?

In an oxygen-deficient atmosphere, one significant effect is the inability for fire to sustain. Fires require a certain concentration of oxygen to maintain combustion and produce heat and light. When the oxygen level drops below approximately 16%—which is below the normal atmospheric level of about 21%—the chemical reaction that fuels the fire is disrupted. This leads to a reduction in combustion efficiency, making it difficult for fires to continue burning or even start.

The other choices reflect different concepts related to fire behavior. Increased combustion efficiency, for instance, implies that a fire burns better or hotter due to higher oxygen availability, which does not occur in an oxygen-deficient environment. Potential for flashover typically relates to the rapid spread of fire in adequate oxygen conditions and heated materials, rather than being a direct result of oxygen deficiency. Lastly, enhancement of ventilation would suggest a means of introducing more oxygen into an environment, countering the conditions of an oxygen-deficient atmosphere rather than aligning with the outcomes of such a deficiency.

Thus, the correct answer emphasizes the fundamental requirement of oxygen for fire development and sustainability.