The main function of the fume hood is exhaust. In the chemical laboratory, various harmful gases, odors, moisture and flammable, explosive and corrosive substances will be produced during the experimental operation. In order to protect the safety of users and prevent the pollutants in the experiment from spreading to the laboratory, a fume hood should be used near the pollution source. If the number of fume hoods is small, it is only used for experiments with particularly harmful and dangerous gases and generating a large amount of heat. Then, the fume hood is only responsible for the auxiliary functions of the test bench.
In order to improve the experimental environment, the experiments carried out on the experimental platform are gradually transferred to the fume hood, which requires the fume hood to have the function most suitable for the equipment. In particular, most new laboratories need air conditioning, so the number of fume hoods should be included in the air conditioning system planning in the preliminary design stage of the building. Because the fume hood plays a very important role in the biochemical laboratory, the number of fume hoods has increased sharply in improving the laboratory environment, labor health conditions and work efficiency. At the same time, ventilation pipes, pipes, wiring and exhaust have become the focus of laboratory construction.
The biggest purpose of using the fume hood is to discharge the harmful gas generated in the experiment and protect the health of experimental researchers, that is, we should have a high degree of safety and superior operability, which requires that the fume hood should have the function of wind speed control.
In order to prevent harmful gases from escaping from the ventilation hood, a certain suction speed is required. The factors that determine the air inlet speed of the fume hood are the heat generated by the experimental content and the relationship with the ventilation times. Mainly the experimental content and the properties of harmful substances. According to national standards, the wind speed on the surface of the fume hood is 0.5m/s ± 10%. In order to ensure this wind speed, the exhaust fan shall have the necessary static pressure, that is, the friction resistance when the air passes through the ventilation duct.
When determining the wind speed, attention must also be paid to noise. The air flow through the pipeline is limited to 7-10m, and noise will be generated if it exceeds 10m. Generally, the noise in the laboratory (indoor background noise level) is limited to 70dba. Increasing the pipeline area will reduce the wind speed and the corrosion resistance to heat and acid-base.
有些通风柜应放在电炉中，有些实验会产生大量的酸和碱以及其他腐蚀性强的有毒有害气体。通风柜柜台、衬里、侧板及选定的水、气等应具有防腐功能。在半导体行业或腐蚀性实验中使用硫酸、硝酸和氢氟酸等强酸也要求通风柜的整体材料必须耐酸和耐碱，通常由不锈钢、PVC 或 PP 材料制成。
Some fume hoods should be placed in electric furnaces. Some experiments will produce a large amount of acid, alkali and other highly corrosive toxic and harmful gases. The counter, lining, side plate and selected water and gas of the fume hood shall have anti-corrosion function. The use of strong acids such as sulfuric acid, nitric acid and hydrofluoric acid in the semiconductor industry or corrosive experiments also requires that the overall material of the fume hood must be acid and alkali resistant, usually made of stainless steel, PVC or PP materials.