What should not be present in any portion of a venting system?

The presence of a fabricated air duct or furnace plenum in a venting system is inappropriate because these components are not designed to handle the combustion gases produced by propane appliances. Venting systems must facilitate the safe and efficient expulsion of these gases outside the structure while preventing the escape of harmful substances back into the living space. The use of a fabricated air duct, which is typically used for air distribution in HVAC systems, can lead to inadequate venting and potential backdrafting of toxic gases, posing serious safety risks.

In contrast, fiberglass insulation, metal duct fittings, and drywall partitions can be utilized in venting systems under specific guidelines. Fiberglass insulation, for example, can sometimes be installed around vent pipes, provided that it is not in direct contact with the vent and allows for the necessary clearance and heat dissipation. Metal duct fittings are commonly used in vent systems due to their durability and fire resistance. Drywall partitions may also be present in areas where venting systems run, ensuring they comply with applicable codes regarding fire safety and installation requirements.