Fume Hood The main functions and categories of fume hoods, fume hoods is an indispensable part of the laboratory ventilation design. In order to allow laboratory staff not to inhale or swallow some toxic, pathogenic or unidentified chemical substances and organisms, the laboratory should be well ventilated. To prevent the absorption of some vapor, gases and particulates (smoke, soot, dust and gas), the contaminants must be removed by means of a fume hood, hood or local ventilation.
① type pumping fume hood: This fume hood is characterized by simple structure, easy manufacturing, suitable for heat generation occasions.
② slit fume hood: slit fume hood is in its top and rear side with exhaust slit, for a variety of different conditions can get good results. But the structure is more complex, making more trouble.
③ Bypass fume hood: When the laboratory to consider the scope of the exhaust cabinet to exclude indoor air, the use of this type of fume hood is ideal, because when the door is fully closed when the ventilation does not affect the room.
④ wind-type fume hood: for the air conditioning system, laboratory or clean laboratory, the use of this type of fume hood is ideal, not only saves energy, but also does not affect the indoor air organization.
⑤ natural ventilation-type fume hood: the advantage is not power; can day and night continuous ventilation (measured by the indoor ventilation up to 6 times / h), is conducive to indoor ventilation; no noise and vibration; because there is no mechanical equipment, easy maintenance ; Simple structure, low cost. But its use is subject to certain conditions, where the toxicity is high and does not produce heat experiments.
The main function
Fume Hood The most important function of the fume hood is the exhaust function, in the chemical laboratory, the experimental operation of a variety of harmful gases, odor, moisture and flammable, explosive, corrosive substances, in order to protect the safety of users , To prevent the spread of contaminants in the laboratory to the laboratory, in the vicinity of the use of fume hoods, the use of a small number of fume hood in the past, only in the particularly harmful and dangerous gases and produce a lot of hot experiments. The fume hood only supports the auxiliary function of the bench. Taking into account the improvement of the experimental environment, the experiments carried out on the bench gradually transferred to the fume hood, which requires the fume hood to have the most suitable for the use of equipment functions. In particular, most of the new laboratories are required to have air conditioning, so in the initial stage of the design of the building will be the number of fume hood into the air conditioning system plan. As the fume hood in the biochemical laboratory occupies a very important position, from improving the laboratory environment, improve labor hygiene conditions, improve work efficiency, etc., the use of fume hoods increased the number of leap. Followed by the ventilation pipes, piping, wiring, exhaust and so have become an important issue in laboratory construction.
The biggest purpose of using the fume hood is to discharge the harmful gases produced in the experiment to protect the health of the experimenter, that is to say, to have a high degree of safety and superior operability, which requires the fume hood to have the following functions:
(5) to control the wind speed function: In order to prevent the escape of harmful gases in the fume hood, need to have a certain suction speed. The factors that determine the rate of inhalation of the fume hood are: the amount of heat generated by the experiment and the relationship with the number of ventilation. The main thing is the experimental content and the nature of the harmful substances. National standards, fume hood surface wind speed of 0.5 m / s ± 10%. In order to ensure such wind speed, the exhaust fan should have the necessary static pressure, that is, the air through the ventilation duct when the friction resistance. Determine the wind speed must also pay attention to the noise problem, through the air flow in the pipeline to 7-10m limit, more than 10m will produce noise, usually laboratory (indoor background noise level) noise limit of 70dBA, increase the pipeline area will be Reduce wind speed (6) heat and acid corrosion resistance. Some of the fume hood to be placed electric furnace, and some experiments produce a large number of acid and alkali and other toxic and harmful gases with a strong corrosive. Fume hood table, liner, side panels and the choice of water Tsui, Qi Tsui, etc. should have anti-corrosion function. In the semiconductor industry or corrosive experiments using sulfuric acid, nitric acid, hydrofluoric acid and other strong acid occasions also require the overall material of the fume hood must be anti-acid, usually made of stainless steel, PVC or PP material.