Compressed Natural Gas (CNG) Certification Practice Exam 2025 - Free CNG Certification Practice Questions and Study Guide

CNG is stored under high pressure because this method allows for a significant volume of gas to be stored in a relatively small space, making it efficient for both storage and transportation. In its gaseous state, natural gas occupies a large volume at atmospheric pressure, so compressing it to high pressures (typically around 3,000 to 3,600 psi) effectively reduces its volume for practical applications, such as fueling vehicles or powering equipment.

This high-pressure storage is essential in ensuring that sufficient quantities of CNG are available when needed, whether in energy production or as a vehicle fuel. Storing CNG at high pressure also helps maintain its energy density, which is crucial for applications where space and weight considerations are critical, such as in compressed natural gas vehicles.

In contrast, storing CNG under low pressure would not allow for the necessary energy density, making it impractical for most uses. Refrigeration is not required for CNG storage since it remains in a gaseous state and at the pressures used for storage, it does not condense into a liquid. Lastly, while CNG is delivered for immediate use in some cases, it is primarily stored for later use, which highlights the importance of high-pressure storage systems.