return

Pointed out the reasons that the gas concerntration in the air return was cuted down.

提出了反风时回风流中沼气浓度降低的原因，对反风时回风流中沼气浓度的变化规律进行了研

The influence for velocity field and temperature field with the difference of height of return air is analysed.

分析了回风口高度对室内空气流动的速度场和温度场的影响。

This article briefly analyses such health security problems as fresh air, return air, indoor air humidity and everyday maintenance of existing air conditioning systems, and presents some suggestions to solve these problems.

本文浅析 了现有空调系统针对健康、安全方面的新风、回风、室内湿度以及空调系统的日常保养维护问 题。