What should gas piping not be laid in contact with?

Gas piping should not be laid in contact with cinders due to several important safety and material integrity considerations. Cinders, being small and abrasive, can cause physical damage to the piping as they can wear down the material over time or create sharp points that might lead to punctures or leaks.

Additionally, cinders may retain moisture, leading to corrosion or degradation of the piping material. Corrosion is particularly dangerous in gas lines, as it can lead to gas leaks and potential hazards to safety. Ensuring that gas piping is not in contact with materials that can cause wear or moisture accumulation is crucial for the long-term integrity and safety of a gas system.

While other options like water, pavement, and wood may present certain issues, they do not share the same level of risk as cinders in relation to abrasion and moisture retention. Therefore, avoiding contact with cinders is a specific directive based on their unique properties and the potential risks they pose to gas piping systems.