In the modern laboratory equipment in the fume hood, the central experimental platform, side Taiwan, drug cabinets, containers counters, cylinder cabinets, etc., which is the biochemical laboratory equipment is responsible for a very important function, is essential equipment The Therefore, the choice of fume hood is an important issue in laboratory construction, must be given enough attention.
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.
In recent years, taking into account the improvement of the experimental environment, the experiment 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:
(1) release function: should have the ventilation cabinet inside the harmful gases generated by the use of gas outside the cabinet, so that after the removal of the outdoor body.
(2) does not return to the function: should have a dust inside the fume hood generated by the exhaust gas from the inside of the fume hood does not reverse the flow into the room function. To ensure the realization of this function, a fume hood with a fan with a single pipe connection is the best way, can not be connected with a single pipe, and only the same room can be connected with the same room, the fan as much as possible Installed at the end of the pipe (or at the top of the pipe).
(3) isolation function: in front of the fume hood should not slide the glass window to separate the inside and outside the fume hood.
(4) Supplementary function: There shall be a passage or replacement device for the inhalation of air from the fume hood when the harmful gas is discharged.
(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. It is generally stipulated that the general non-toxic pollutants are 0.25-0.38 m / s, toxic or dangerous pests are 0.4-0.5 m / s, highly toxic or have a small amount of radioactivity of 0.5-0.6 m / s, 0.5 m / s, and the granules were 1 m / s.
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 the wind speed, also reduce the noise, taking into account the pipeline funding and construction problems, we must carefully select the power of pipes and exhaust fans.
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 the wind speed, also reduce the noise, taking into account the pipeline funding and construction problems, we must carefully select the power of pipes and exhaust fans.
(6) heat and acid corrosion function: 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, must be made of stainless steel or PVC material.
