What is a requirement for the storage cylinders of compressed natural gas?

The requirement for storage cylinders of compressed natural gas (CNG) is that they must be aboveground on stable noncombustible foundations. This is important for safety and environmental considerations. Aboveground storage allows for easier monitoring and access for maintenance or inspections, while noncombustible foundations minimize the risk of fire hazards. Stable foundations ensure that the cylinders remain secure and reduce the risk of tipping or structural failures, which could lead to dangerous leaks or explosions.

The choice to require aboveground storage rather than underground storage is based on the need for visibility and easier emergency response in case of an incident. Storing cylinders in a way that allows for direct access and visibility also helps in complying with safety regulations. For example, underground storage can complicate inspections and make it harder to identify leaks.

The other options, such as insulating with foam or painting them any color, do not meet the primary safety and operational standards necessary for CNG cylinder storage and could potentially lead to safety risks.