In cold climates, uninsulated single-wall pipe should not be used for what?

In cold climates, uninsulated single-wall pipe should not be used for venting gas appliances due to the risk of condensation and the potential for creating dangerous situations. When gas appliances are vented, they produce flue gases that contain moisture. If the venting pipe is uninsulated and exposed to cold temperatures, this moisture can condense inside the pipe, leading to the accumulation of liquid within the vent system. This could potentially block the venting path, allowing carbon monoxide and other harmful gases to leak back into the living space. Proper venting is critical for safety and efficiency, and using insulated or properly rated venting systems can help prevent these hazards.

The other options pertain to uses that either do not involve gas venting or are typically regulated differently, making them less relevant in the context of the specific issues related to venting appliances in cold climates.