The basic principle of airflow organization in white iron ventilation engineering is that the exhaust outlet should be as close as possible to harmful sources or heat dissipation equipment, and the air supply outlet should be as close as possible to the operating location or the place where personnel frequently stay.

通风管道是通风系统的重要组成部分，通风管道系统设计的目的，白铁通风工程是要合理地组织空气流动，在保证使用效果的前提下，合理确定风管的结构、布置和尺寸，使系统的初投资和运行费用综合较低。从理论上说，在送、排风管进入土建竖井处设与不设层流板其阻力系数相差可达10倍，从某工程实际检测中发现，同样型号的的风机近似的风管和风口，用作送风时风量为9780m3/h，用作排风时风量为6560m3/h，差距达成22.7%。风口选用偏小也是系统阻力增大，风量下降的一个因素。

Ventilation ducts are an important component of the ventilation system. The purpose of designing a ventilation duct system is to organize air flow reasonably in a white iron ventilation project. On the premise of ensuring the effectiveness of use, the structure, layout, and size of the air ducts should be reasonably determined, so as to comprehensively reduce the initial investment and operating costs of the system. In theory, the difference in resistance coefficient between installing and not installing laminar flow plates at the point where the supply and exhaust ducts enter the civil vertical shaft can be up to 10 times. From an actual inspection of a certain project, it was found that the similar air ducts and tuyeres of the same model of fan have an air flow rate of 9780m3/h when used for air supply and 6560m3/h when used for exhaust, with a difference of 22.7%. The smaller selection of air vents is also a factor in increasing system resistance and decreasing air volume.

根据风机的特性曲线可以看出，风机可以在各种不同的风量下工作，风机在特性曲线的某一工作点上，风机的风压与系统中的压力得到平衡，就确定了系统的风量。

According to the characteristic curve of the fan, it can be seen that the fan can operate at various air volumes. At a certain working point on the characteristic curve, the fan's air pressure is balanced with the pressure in the system, and the system's air volume is determined.

设置防火阀的主要目的是防止火灾通过风管漫延。推荐采用将卫生间排气支管接入排气竖井井上升60mm的防止回流措施，其具有结构简单，造价低、运行可靠等特点，由于采用弯头进竖井，支管与主管气流方向相同， 此部分局部阻力小，其竖井排风总阻力并不一定由于竖井面积减少一点而增大。

The main purpose of setting fire dampers is to prevent fires from spreading through ducts. It is recommended to take measures to prevent backflow by connecting the bathroom exhaust branch pipe to the exhaust shaft and raising it by 60mm. It has the characteristics of simple structure, low cost, and reliable operation. Due to the use of elbows to enter the shaft, the branch pipe and the main pipe have the same airflow direction, and the local resistance in this part is small. The total resistance of the vertical shaft exhaust does not necessarily increase due to a slight reduction in the shaft area.