Where is gas piping prohibited inside a building?

Gas piping is prohibited in elevator shafts for several safety and operational reasons. Elevator shafts are vertical spaces that serve as the pathway for elevators, and any flammable gas, such as liquefied petroleum gas, poses a significant risk in these enclosed environments. If a gas leak were to occur within an elevator shaft, it could lead to dangerous accumulations of gas, increasing the risk of explosion or fire, especially given the electrical equipment commonly found in such areas.

Additionally, elevator operations may involve moving parts that could create a potential ignition source, making it even more crucial to keep gas piping out of these spaces. NFPA 58 emphasizes safety by mandating these restrictions to minimize risk in areas that involve mechanical movement and can be difficult to ventilate appropriately.

The other choices, while they may have specific regulations depending on context, do not have the same inherent hazards associated with them as elevator shafts do. For example, window sills and outside walls may have designated areas where gas piping can be installed if done according to code compliance, and basements, while they have their own risks, are typically areas where gas piping can be securely placed if correctly installed and ventilated.