Why should gas piping not be run through ducts or air handling spaces?

Gas piping should not be run through ducts or air handling spaces primarily to avoid gas leakage affecting airflow. If there is a leak in the gas piping located in these areas, it can contaminate the air supply and potentially create a hazardous situation, including the risk of fire or explosion. Ensuring that gas piping remains outside of air handling spaces minimizes the risk of gas escaping into occupied areas where air is circulated, maintaining safety for the building's occupants.

The other considerations, while potentially relevant in different contexts, do not address the critical safety concerns associated with gas leaks in air handling systems. Reducing pressure loss does not relate to the safety implications of leaking gas, and minimization of installation costs and compliance with decorative standards are secondary factors that do not address the fundamental safety issue of gas leaks.