NATE Gas Heating Practice Exam

Which of the following gases is typically heavier than air?

1. Methane

2. Natural gas

3. Butane

4. Hydrogen

The correct answer is: Butane

Butane is indeed heavier than air, which is why it is the correct choice in this context. Density is an important factor when considering the behavior and safety of gases in various applications, such as heating systems. Butane has a molecular weight of about 58.12 g/mol, and its density is approximately 2.48 times that of air. When released into the atmosphere, butane will tend to accumulate in low-lying areas because it does not disperse as easily as lighter gases. This characteristic is crucial for safety considerations, particularly in situations where gas might leak, as it can create a potential hazard by pooling in enclosed or low-vented spaces. The other gases listed have different properties: methane (the primary component of natural gas) is lighter than air, with a molecular weight of about 16.04 g/mol, making it rise in the atmosphere. Natural gas, primarily composed of methane, shares this characteristic. Hydrogen is the lightest gas available, with a molecular weight of about 2.02 g/mol, and it rapidly rises when released. Understanding the relative density of these gases helps in managing their safe usage in heating and other applications.