Natural gas piping cannot be run through which of the following?

Natural gas piping must not be run through air ducts, clothes chutes, and chimneys for several important safety and operational reasons. Air ducts are designed for air distribution and running gas piping in them could lead to gas leaks entering living spaces or mixing with air that people breathe, posing serious health and explosion risks. Clothes chutes are not meant to accommodate gas piping, as any potential leak could allow natural gas to accumulate in enclosed spaces, leading to hazardous conditions.

Chimneys serve a completely different purpose - they are designed to vent combustion gases from appliances safely outside. Having gas piping running through chimneys compromises their function and can result in backdrafting of hazardous combustion products into the home. This can create a dangerous environment for occupants.

Overall, the prohibition of running natural gas piping through such structures is fundamentally about maintaining safety standards, preventing potential gas leaks, and ensuring that appliances operate safely and efficiently.