The  use of ventilation methods to improve the air environment of the  workshop, on the one hand in the local site or the entire workshop does  not meet the health standards of dirty air discharged to the outside, on  the other hand, the fresh air or purified health requirements into the  room. We call the former exhaust, the latter known as the wind.
      In  the centralized place to produce harmful substances, set the capture  device, the excretion of harmful substances to control the spread of  harmful substances to the indoor, this ventilation method known as the  local exhaust. This is the most effective way to prevent air and dust.
The local exhaust system consists of the following parts:
  (1) local exhaust hood
       Partial hood is used to catch harmful substances. Its performance has a direct impact on the technical and economic indicators of the local exhaust system. Good local exhaust hood, such as a closed cover, as long as the smaller air volume can get a good work results. Due to the different production equipment and operation, the form of the exhaust hood is varied.
  (2) ducts
       Ventilation system in the pipeline to call the gas duct, which the system of various equipment or components into a whole. In  order to improve the economy of the system, the gas flow rate in the  duct should be selected reasonably, and the pipeline should be short and  straight. Ducts are usually made of smooth material, such as: thin steel  plate, PVC board, sometimes with concrete, brick and other materials.
  (3) dust removal, purification equipment
       In  order to prevent air pollution, when the discharge of harmful  substances in the air exceeds the discharge standards, must be treated  with purification equipment to meet the emission standards, the people  discharged into the atmosphere. Purification equipment, sub-dust and harmful gas purification device two categories.
  (4) fan
       The fan provides power to the mechanical exhaust system to provide air flow. In order to prevent the wear and corrosion of the fan, it is usually placed behind the purification equipment.
       If  only the local location of the exhaust or air, that is, local  ventilation; if the entire workshop for ventilation or air, then a  comprehensive ventilation. Usually,  according to the scope of the ventilation system, ventilation can be  divided into local ventilation, comprehensive ventilation and accident  ventilation. Local  ventilation system is divided into two kinds of local into the wind and  local exhaust, they are the use of local airflow, so that the local  workplace from harmful pollution, resulting in a good air environment.