What should be avoided in the selection of hoses for CNG applications?

Answer: B — Hoses made of unknown materials

In the selection of hoses for CNG applications, it is crucial to avoid hoses made of unknown materials. The integrity and safety of CNG systems depend significantly on the materials used for hoses. Hoses constructed from unknown or unverified materials may not meet the stringent requirements for pressure tolerance, chemical resistance, and durability that CNG demands. Using hoses that are not certified for CNG use can lead to failures, leaks, and catastrophic incidents. Each component in a CNG system must be specifically designed and tested for the conditions it will encounter to ensure safety and reliability. Therefore, it's essential to choose hoses that have established specifications and are made from recognized materials that have been proven to perform well in natural gas applications. The other options are elements that provide advantages, such as high pressure ratings, corrosion resistance, and flexibility, indicating that they are suitable for the CNG environment.