In some places where harmful substances are concentrated, devices for collecting and removing harmful substances have been set up to control the indoor diffusion of harmful substances. This type of ventilation is called local exhaust. This is the most effective way of ventilating gas and dust.

　　济南部分消防排烟管道由以下部分组成:

　　Some fire fighting and smoke exhaust pipes in Jinan are composed of the following parts:

　　1)部分排气罩

　　1) Partial exhaust hood

　　排气罩的一部分用来捕捉害虫。其性能直接影响到某些排气系统的技术经济指标。排风罩性能好的部件，如闭式排风罩，只需少量的空气即可获得良好的工作效果。由于不同的消耗设备和操作方式，排气罩有多种方式。

　　Part of the exhaust hood is used to catch pests. Its performance directly affects the technical and economic indicators of some exhaust systems. The components with good performance of exhaust hood, such as closed exhaust hood, need only a small amount of air to achieve good working effect. Due to different consumption equipment and operation mode, exhaust hood has many ways.

　　2)管道

　　2) Pipeline

　　在通风系统中，输送空气的管道称为风管。它们将系统中的各种设备或组件作为一个整体连接起来。为了提高系统的经济性，应合理选择管道内的气速，管道应短而直。风管通常由外部润滑的材料制成，如:薄钢板、PVC板，有时还有混凝土、砖等材料。

　　In the ventilation system, the air duct is called the air duct. They connect various devices or components in the system as a whole. In order to improve the economy of the system, the gas velocity in the pipeline should be reasonably selected, and the pipeline should be short and straight. Air ducts are usually made of externally lubricated materials, such as thin steel plate, PVC board, and sometimes concrete, brick and other materials.

　　3)除尘净化设备

　　3) Dust removal and purification equipment

　　为了避免空气污染，当有害物质排放到空气中的量超过排放标准时，必须用净化设备进行处理，当达到排放标准时，将其排放到大气中。净化设备可分为除尘器和有害气体净化装置。

　　In order to avoid air pollution, when the amount of harmful substances discharged into the air exceeds the discharge standard, it must be treated with purification equipment, and when the discharge standard is reached, it will be discharged into the atmosphere. Purification equipment can be divided into dust collector and harmful gas purification device.

　　4)风扇

　　4) Fans

　　风扇捕捉空气运动到机械排气系统的动力。为避免风机磨损和腐蚀，通常将风机置于清洗设备的后方。

　　The fan captures the power of the air moving to the mechanical exhaust system. In order to avoid wear and corrosion of the fan, the fan is usually placed behind the cleaning equipment.

　　局部通风仅当局部通风或送风停止时;如果整个车间的排风或送风停止，应充分通风。一般根据通风系统运行范围的不同，可将通风分为局部通风、全通风和事故通风。部分通风系统分为进气部分和排气部分两大类，它们都是部分气流的应用，部分工作场所受到有害污染，形成良好的空气环境。

　　Local ventilation is only when the local ventilation or air supply stops; if the exhaust or air supply stops in the whole workshop, it should be fully ventilated. Generally, according to the different operating range of ventilation system, ventilation can be divided into local ventilation, full ventilation and accident ventilation. Part of the ventilation system is divided into two categories: intake part and exhaust part. They are all part of the application of air flow. Some workplaces are harmfully polluted and form a good air environment.