return air duct

例句：

1. 1. The returnair duct is designed toimprove the efficiency of the heating system.
   回风管道的设计旨在提高供暖系统的效率。
2. 2.The technicians were instructed to inspect thereturn air ducts for any signsof damage.
   技术人员被指示检查回风管道是否有任何损坏的迹象。
3. 3. The returnair ducts arecrucial for maintaining proper airflowin the building.
   回风管道对于保持建筑物内空气流通至关重要。