HVAC Journeyman Practice Exam

Return air ducts serving a dwelling unit can be constructed from combustible materials under specific conditions. In residential settings, building codes generally allow for the use of combustible materials in the construction of return air ducts as long as they comply with local code requirements and safety standards.

When return air ducts are made of combustible materials, it is vital that the installation is done properly to limit potential fire hazards. Local regulations often provide guidelines on the fire resistance ratings required for ducts, which ensures that they are safe for use even in the event of a fire. Therefore, while non-combustible and rated materials may be preferred in certain scenarios, the allowance for combustible materials provides flexibility in residential HVAC system design, making it a practical choice for many applications.

In summary, the permissibility of combustible construction for return air ducts in a residential unit means that such materials can be utilized effectively and safely when adhering to established guidelines and building codes.