NATE Gas Heating Practice Exam

Which of the following is a natural product of combustion?

1. Water vapor

2. Carbon monoxide

3. Carbon dioxide

4. All of the above

The correct answer is: All of the above

The correct answer is that all of the listed substances—water vapor, carbon monoxide, and carbon dioxide—are natural products of combustion. During the combustion process, hydrocarbon fuels react with oxygen, resulting in several byproducts depending on the completeness of the combustion. When combustion is complete, the primary products are carbon dioxide and water vapor. This occurs when there is an adequate supply of oxygen, allowing the fuel to burn efficiently. In this scenario, the carbon atoms in the fuel combine with the oxygen to form carbon dioxide, and the hydrogen atoms combine with oxygen to form water vapor. However, if the combustion process is incomplete, which can happen in situations where there is insufficient oxygen, carbon monoxide is produced instead. Carbon monoxide is a colorless and odorless gas that can be hazardous, and it forms when carbon atoms do not fully oxidize to carbon dioxide. Thus, since both complete and incomplete combustion can produce these substances, it's accurate to say that all of the mentioned options—water vapor, carbon monoxide, and carbon dioxide—are natural products resulting from combustion processes.