Which gas is NOT released into the atmosphere when fuels are burned?

Oxygen is not released into the atmosphere when fuels are burned because combustion typically consumes oxygen rather than producing it. Fuels such as hydrocarbons react with oxygen during combustion, leading to the production of various waste gases, including carbon dioxide, sulfur dioxide, and oxides of nitrogen. The process of combustion requires oxygen to oxidize the fuel, and in doing so, it transforms the fuel into other gases and compounds. Hence, while other gases are emitted as byproducts, oxygen itself is depleted from the environment during the burning process.