NATE Gas Heating Practice Exam

In order to achieve complete combustion with natural gas, how many cubic feet of air must each cubic foot of gas combine with?

1. 5 cubic feet

2. 10 cubic feet

3. 15 cubic feet

4. 20 cubic feet

The correct answer is: 10 cubic feet

To achieve complete combustion of natural gas, each cubic foot of gas typically requires about 10 cubic feet of air. Natural gas primarily consists of methane, and during combustion, it reacts with oxygen in the air to produce carbon dioxide, water vapor, and energy. For this reaction to occur efficiently and produce minimal pollutants, the right balance of fuel (natural gas) and oxidizer (air) is crucial. The stoichiometric equation for methane combustion shows that complete combustion necessitates a specific amount of oxygen, which can be derived from air. Air contains about 21% oxygen, so to ensure complete combustion and not produce carbon monoxide or other harmful byproducts, it's essential to supply the right volume of air. This requirement underlines the importance of maintaining proper air-to-fuel ratios in heating systems and appliances that use natural gas, ensuring they operate safely and efficiently. Understanding this ratio is fundamental to anyone working in the gas heating field, as it impacts overall system performance and emissions.