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The main function of the Fume hood is the exhaust function. In the chemical laboratory, various harmful gases, odors, moisture and flammable, explosive and Corrosive substance are generated during the experimental operation. In order to protect the safety of users and prevent the spread of pollutants in the experiment to the laboratory, Fume hood should be used near the pollution source. In the past, there were few Fume hood, Only used in particularly harmful and dangerous gases and experiments that generate a large amount of heat. The Fume hood only serves as the auxiliary function of the test bench. Considering the improvement of the experimental environment, the experiments carried out on the experimental platform are gradually transferred to the Fume hood, which requires that the Fume hood should have functions suitable for the use of equipment. In particular, most new laboratories require air conditioning, so the number of Fume hood to be used should be included in the air conditioning system plan in the preliminary design stage of the building. Since Fume hood occupies a very important position in the biochemical laboratory, the number of Fume hood is increasing by leaps and bounds from the aspects of improving laboratory environment, improving labor hygiene conditions, and improving work efficiency. Subsequently, ventilation ducts, piping, wiring, and exhaust have become important topics in laboratory construction.

The purpose of using the Fume hood is to discharge the harmful gas generated in the experiment and protect the health of the experimental personnel, that is, to have a high degree of safety and superior operability, which requires that the Fume hood should have the following functions:

(1) Release function: It shall have a mechanism to absorb the harmful gas generated inside the Fume hood by absorbing the gas outside the fume hood, so that it can be diluted and discharged outside.

(2) Non backflow function: It shall have the function of non backflow of harmful gas into the room from the inside of the Fume hood by the airflow generated by the exhaust fan. To ensure the realization of this function, it is a conventional method to connect a Fume hood and a ventilator with a single pipe, which cannot be connected with a single pipe, and is only limited to the parallel connection of the same room on the same floor. The ventilator should be installed at the end of the pipe (or at the top of the floor) as far as possible.

(3) Isolation function: the front of the Fume hood shall be equipped with a non sliding glass window to separate the inside and outside of the Fume hood.

(4) Supplementary function: It shall have a channel or an alternative device for drawing air from outside the Fume hood when discharging harmful gases.

(5) Wind speed control function: in order to prevent harmful gases from escaping from the Fume hood, a certain suction speed is required. The factors that determine the suction speed of the Fume hood inlet air are: the heat generated by the experimental content and the relationship with the Air changes per hour. The main focus is on the experimental content and the properties of harmful substances. Generally, the standard for non-toxic pollutants is 0.25-0.38m/s, for toxic or hazardous substances is 0.4-0.5m/s, for highly toxic or slightly radioactive substances is 0.5-0.6m/s, for gaseous substances is 0.5m/s, and for granular substances is 1m/s. To ensure such wind speed, the exhaust fan should have the necessary static pressure, which is the frictional resistance of air when passing through the ventilation duct. When determining the wind speed, attention must also be paid to the issue of noise. When air flows through the pipeline, it is limited to 7-10m, and exceeding 10m will generate noise. Usually, the noise limit for the laboratory (indoor background noise level) is 70dBA. Increasing the cross-sectional area of the pipeline will reduce the wind speed, thus reducing noise. Considering the funding and construction issues of the pipeline, it is necessary to carefully select the power of the pipeline and exhaust fan.

(6) Heat resistance and acid and alkali corrosion resistance: some Fume hood need to be equipped with electric furnaces, and some experiments produce a large number of toxic and harmful gases such as acid and alkali, which are extremely corrosive. The table top, lining plate, side plate of the Fume hood and the selected water nozzle and air nozzle shall have anti-corrosion function. When strong acids such as sulfuric acid, nitric acid and hydrofluoric acid 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 must be made of stainless steel or PVC.