The main function of the Laboratory Fume Hood is the exhaust function. In the chemical laboratory, various harmful gases, odors, moisture, and flammable, explosive and corrosive substances are generated during the experimental operation to protect the user's safety. To prevent the spread of pollutants from the laboratory to the laboratory, use a Laboratory Fume Hood near the source of the pollution. In the past, the number of Laboratory Fume Hoods used was relatively small, and they were used only in particularly harmful and dangerous gases and in experiments where large amounts of heat were generated. The Laboratory Fume Hood is only responsible for the auxiliary functions of the lab bench. In recent years, taking into account the improvement of the experimental environment, the experiments carried out on the experimental bench were gradually transferred to the Laboratory Fume Hood, which required that the Laboratory Fume Hood should have the most suitable function for the equipment.
The new laboratory design has air conditioning, so the number of Laboratory Fume Hoods used must be included in the air conditioning system plan. Because the Laboratory Fume Hood occupies a very important position in biochemical laboratories, the use of Laboratory Fume Hoods has increased from the perspectives of improving the laboratory environment, improving labor hygiene conditions, and improving work efficiency. Followed by the ventilation ducts, piping, wiring, exhaust, etc. have become an important task of laboratory construction.
The main purpose of using the Laboratory Fume Hood is to discharge the harmful gases produced in the experiment and protect the health of the experimental personnel, that is, to have a high degree of safety and superior operability. This requires that the Laboratory Fume Hood should have the following functions:
(1) Release function: It should have means for absorbing the harmful gases generated inside the Laboratory Fume Hood to absorb the gas outside the cabinet and dilute it to outside.
(2) No backflow function: The air flow generated by the exhaust fan inside the Laboratory Fume Hood shall have the function of preventing harmful gases from flowing into the room from inside the Laboratory Fume Hood. To ensure the realization of this function, a single Laboratory Fume Hood connected to a single fan is the best method. It cannot be connected by a single pipe. It is also limited to the parallel connection of the same room in the same floor. The fan is installed as far as possible. At the end of the pipe (or at the roof).
(3) Isolation function: Separate the inside and outside of the Laboratory Fume Hood with a non-sliding glass window in front of the Laboratory Fume Hood.
(4) Supplementary function: There should be a channel or an alternative device for sucking in air from outside the Laboratory Fume Hood when harmful gases are discharged.
(5) Control of wind speed function: In order to prevent harmful gases in the Laboratory Fume Hood from escaping, a certain suction speed is required. The factors that determine the suction speed of the Laboratory Fume Hood's air intake are: the amount of heat generated by the experiment content and the relationship with the number of air changes. The main thing is the nature of the experiment and the nature of the pest. It is generally stated that generally non-toxic pollutants are 0.25-0.38 m/s, toxic or dangerous pollutants are 0.4-0.5 m/s, highly toxic or slightly radioactive is 0.5-0.6 m/s, and gaseous substances are 0.5m/s, granular 1m/s. In order to ensure such a wind speed, the exhaust fan should have the necessary static pressure, that is, the frictional resistance when the air passes through the ventilation duct. When determining the wind speed, we must also pay attention to the noise problem. When the air flows in the pipeline, it is limited to 7-10m. If it exceeds 10m, noise will be generated. Usually, the laboratory noise (indoor background noise level) is limited to 70dB (A). The cutting area will reduce the wind speed and reduce the noise. In view of the funding and construction issues of the pipeline, the power of the pipeline and the exhaust fan must be carefully selected.
(6) Heat and acid and alkali corrosion resistance: Some of the Laboratory Fume Hoods need to be equipped with electric furnaces. Some experiments produce a lot of toxic and harmful gases such as acids and alkalis that are extremely corrosive. The countertops, liners, side plates, and optional nozzles and nozzles of Laboratory Fume Hoods shall have anti-corrosion function.