The function 1 of the ductless fume hood is to control the wind speed:in order to prevent the escape of harmful gases in the ductless fume hood,a certain suction speed is required.The factors that determine the suction speed of the fume hood inlet air include the heat generated in the experiment and the relationship between the heat and the number of air changes.The main content is the experimental content and the nature of harmful substances.The standard stipulates that the surface wind speed of ductless fume hood is 0.5m/s±10%.In order to ensure such wind speed,the exhaust fan should have the necessary static pressure,that is,the friction resistance when the air passes through the duct of the ductless fume hood.
The function 2 of the ductless fume hood is heat resistance and acid and alkali corrosion resistance.Some of the ductless fume hoods need to be equipped with electric furnaces,and some experiments produce a large number of toxic and harmful gases such as acid and alkali with strong corrosivity.The countertop,lining plate,side plate and selected water nozzle and air nozzle of the fume hood shall have anti-corrosion function.When sulfuric acid,nitric acid and other strong acids are used in the semiconductor industry or corrosive experiments,it is also required that the overall material of the fume hood must be acid and alkali resistant,and it is usually made of stainless steel,PVC or PP materials.
The ductless fume hood does not need external pipes,and the top is equipped with fan and filter.Turn on the switch and the fan operates to form negative pressure in the cabinet to ensure that chemicals will not overflow.The wind direction of the main body is from bottom to top,so that all the air in the cabinet is filtered by the filter,and the clean air is discharged from the top air outlet.On the one hand,it can purify the chemicals volatilized in the cabinet,and on the other hand,it can also purify the air in the laboratory by entering the cabinet.Installation and commissioning are simple and convenient,energy saving and environmental protection,do not consume air-conditioning air,purify the air in the laboratory,and protect the health of personnel.
