Which combustion product can displace oxygen?

Carbon dioxide is a combustion product that can displace oxygen due to its physical properties. When a fire burns, it consumes oxygen and produces heat, light, water vapor, and various gases, including carbon dioxide. In a confined space, an increase in carbon dioxide concentration can reduce the availability of oxygen for breathing and combustion, leading to asphyxiation and further inhibiting the fire's ability to burn since oxygen is vital for combustion.

Water vapor, while it is a product of combustion, does not displace oxygen as it is not capable of replacing or reducing its concentration in the air. Hydrogen gas, although potentially flammable, does not commonly result from the combustion processes we're considering in this context and does not have the same displacing effect. Nitrogen, present in the atmosphere, is an inert gas that does not react under normal combustion conditions and does not contribute to oxygen displacement in a significant way. Thus, carbon dioxide is recognized for its role in reducing the available oxygen, particularly in confined spaces during fire situations.