Red Seal Gasfitter — Class B Practice Exam

Which of the following gases is NOT classified as a fuel gas?

1. Natural gas

2. Propane

3. Butane

4. Oxygen

The correct answer is: Oxygen

Oxygen is not classified as a fuel gas because it does not serve as a source of energy in combustion processes. Instead, oxygen is an oxidizing agent that supports combustion by reacting with fuel gases like natural gas, propane, or butane. These fuels release energy when they burn in the presence of oxygen. Natural gas, propane, and butane are all hydrocarbon gases that produce heat and energy when they are burned, making them suitable as fuel gases for heating, cooking, and industrial processes. Understanding the distinction between fuel gases and oxidizers like oxygen is essential in the field of gasfitting and combustion science, as it highlights the roles these gases play in energy production and the safety measures needed when handling them.