MCC-NH Gas Fitters Practice Exam

What type of gas is used in a leak check?

1. Inert gas

2. Combustible gas

3. Natural gas only

4. Helium

The correct answer is: Combustible gas

The appropriate choice for the type of gas used in a leak check, specifically when identifying leaks in gas systems, is a combustible gas. This is primarily because natural gas, which is a common combustible gas, is often used as a medium for testing systems for integrity by checking for leaks. Leak checks typically involve introducing a combustible gas into the system and observing for any signs of gas escaping, which would indicate a leak. The specific properties of combustible gas make it suitable for detecting leaks as it can easily accumulate and be ignited, allowing for both visual and odor recognition of potential gas escapes. In context, while inert gases such as nitrogen or helium can be used in specific leak detection applications (often in more controlled environments), combustible gases are much more common in standard gas fitting and leak checking practices for residential and commercial installations. Helium, although effective due to its small molecular size and ability to escape from minor leaks, is not the typical choice used in most gas fitting scenarios.