Fume hood is an essential part of laboratory furniture. It has the function of ventilation and ventilation in the laboratory.
The structure of the ventilation cabinet is up and down, and the top of the cabinet is provided with exhaust holes, which can be installed with fans.
There are deflectors, circuit controlled touch switches, power sockets, etc. in the cabinet, * * * windows are made of toughened glass, which can move left and right or up and down. For human operation.
The lower cabinet adopts the experimental side table style, with a table top and a cabinet body below. Small water cup and faucet can be installed on the table.
The materials of the fume hood are various, including all steel, steel wood, all wood, aluminum wood, plastic steel, PVC structure, etc.

1、 Brief introduction of fume hood
Fume hood is an essential part of laboratory furniture. It has the function of ventilation and ventilation in the laboratory.
The structure of the fume hood is up and down type, and the top of the fume hood has an exhaust hole, which can be installed with a fan. There are deflectors, circuit controlled touch switches, power sockets, etc. in the cabinet, * * * windows are made of toughened glass, which can move left and right or up and down. For human operation. The lower cabinet adopts the style of experimental side table, with a table top and a cabinet body below. Small water cup and tap can be installed on the table. The materials of the fume hood are various, including all steel, steel wood, all wood, aluminum wood, plastic steel, PVC structure, etc.

2、 Selection of fume hood
The fume hood is not a separate equipment, the change of external environment will affect the performance of fume hood. At the same time, the fume hood and its control system will also affect its surrounding environment, when you choose the fume hood:
First of all, we must consider the factors of the whole system, such as the space of the laboratory, the ventilation control system of the building, the arrangement of the exhaust pipeline, the placement of the fume hood, etc. the R & D personnel and system engineers of Shanghai Beiyou are willing to work with you and the Design Institute to provide a safe and comfortable overall design and planning for your laboratory.
Secondly, you need to determine which type of fume hood you need. When choosing, you can usually measure it according to the following factors:
1. upper cabinet:
There are three styles: standard style, low desk style and floor style.
Whether the surface wind speed of the fume hood meets the safety wind speed requirement of the international standard: 0.5m/s (the international standard stipulates that only when the surface wind speed reaches 0.5m/s can the harmful gas in the fume hood be effectively captured).
Whether the opening height of the fume hood is suitable to meet your demand for operating space.
Ventilation control system: constant air volume, variable air volume or adaptive control system.
Lining material: PP, glass fiber or polyethylene resin, etc.
Whether the raw material of the regulating door adopts safety glue glass, whether the design conforms to the human mechanics, and makes the operator pull freely.
2. Table part:
Whether the table top adopts a safe dish design, so that the user can clean the table and prevent the leakage of toxic liquid.
Whether the material of the table meets the needs of your experiment and resists the corresponding erosion and high temperature.
Whether the cup slot or sink is installed, and whether the installation position is reasonable.
Whether the design of air outlet is reasonable.
3. Bottom cabinet part:
Whether the material is strong and durable, whether it is fireproof material, whether it can resist the erosion of acid-base environment in the laboratory.
Whether the power supply is reasonable and safe.
Whether it is convenient for maintenance of water, electricity and gas systems.
Whether the bottom cabinet needs air extraction design, so that you can place volatile drugs.
When you have basically selected the model, style and size of the fume hood, you can determine what you need according to the following conditions.
4. Accessories:
Water source: distilled water, pure water or reverse osmosis, etc.
Gas source: nitrogen, oxygen or air, etc.
The selection of electrical system should consider: model, voltage, riot resistance, durability and so on.
For aesthetic reasons, whether sealing plate is required.

3、 Main functions of fume hood
The most important function of fume hood is the exhaust function. In chemical laboratory, all kinds of harmful gases, odors, moisture, flammable, explosive and corrosive substances are produced during 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, the number of fume hoods used was less, only in special laboratory It can be used in the experiment of harmful and dangerous gas and producing a lot of heat. The fume hood is only responsible for the auxiliary function of the experimental platform. In recent years, in order to improve 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 the most suitable function for the use of equipment. In particular, most of the newly-built laboratories require air conditioning, so in the preliminary design stage of the building, the number of ventilators should be included in the air conditioning system plan. As the fume hood occupies a very important position in the biochemical laboratory, the number of fume hoods has increased by leaps and bounds from the aspects of improving the laboratory environment, improving labor hygiene conditions, and improving work efficiency. Subsequently, the ventilation pipe, piping, wiring, ventilation and so on have become an important topic of laboratory construction.

The biggest purpose of using the fume hood is to exhaust the harmful gas produced in the experiment and protect the health of the experimental personnel, that is to say, it should have a high degree of safety and superior operability, which requires that the fume hood should have the following functions:
(1) Release function: it should have the 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 should have the function that the airflow generated by the exhaust fan inside the fume hood will not reverse the harmful gas into the room from the interior of the fume hood. In order to ensure the realization of this function, it is the best way to connect a fume hood and a fan with a single pipe. The connection with a single pipe is not allowed, and it is only limited to the parallel connection of the same room on the same floor. The fan should be installed at the end of the pipe (or at the top of the floor) as far as possible.
(3) Isolation function: in front of the ventilation cabinet, there should be a glass window without sliding to separate the inside and outside of the ventilation cabinet.
(4) Supplementary function: it should have a channel or alternative device to inhale air from outside the fume hood when discharging harmful gas.
(5) Wind speed control function: in order to prevent harmful gas 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 ventilation times. The main contents are the content of the experiment and the nature of the harmful substances. It is generally stipulated that the general non-toxic pollutant is 0.25-0.38m/s, the toxic or dangerous harmful substance is 0.4-0.5m/s, the highly toxic or a small amount of radioactivity is 0.5-0.6m/s, the gaseous substance is 0.5m/s, and the granular substance is 1m / s. In order to ensure such a wind speed, the exhaust fan should have the necessary static pressure, that is, the frictional resistance of air passing 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 is more than 10m, the noise will be generated. Generally, the noise limit value of the laboratory (indoor background noise level) is 70dba. Increasing the cut area of the pipeline will reduce the wind speed, that is to say, reduce the noise. Considering the funds and construction problems of the pipeline, we must carefully select the power of the pipeline and exhaust fan.
(6) Heat resistance and acid and alkali corrosion resistance function: some of the fume hood should be equipped with electric furnace, and some experiments produce a large number of acid and alkali and other toxic and harmful gases, which are highly corrosive. The countertop, lining plate, side plate, water nozzle and air nozzle of the fume hood shall have anti-corrosion function. When sulfuric acid, nitric acid, hydrofluoric acid and other strong acids are used in the semiconductor industry or corrosive experiments, the overall material of the fume hood must be acid and alkali resistant, and must be made of stainless steel or PVC.

4、 Category of fume hood
According to the classification of ventilation mode, fume hood can be divided into three types: upper exhaust type, lower exhaust type and simultaneous upper and lower exhaust type. In order to ensure the uniform wind speed in the working area, the lower exhaust type should be adopted for the fume hood in the cold process, and the upper exhaust type should be adopted for the fume hood in the hot process. For the process with unstable calorific value, the upper and lower exhaust outlets can be set up, and the ratio of the upper and lower exhaust air volume can be adjusted with the change of calorific value in the fume hood, so as to obtain the uniform wind speed.
The fume hood is also divided into three categories according to the air inlet mode. Through the indoor air circulation in the cabinet, it is called full exhaust type, which is widely used.
When the fume hood is set in the room with heating or temperature and humidity control requirements, in order to save energy consumption of heating and air conditioning, the way of taking supply air from the outside and circulating in the cabinet and then discharging out of the room is called make-up fume hood.
Another is the variable air volume control type ventilation cabinet. The ordinary constant air volume system needs to manually adjust the air valve of fixed blade, adjust the exhaust air volume of the ventilation cabinet, and reach the desired surface wind speed when the valve is adjusted to a certain angle. VAV control is to change the air volume to a given surface wind speed by adjusting the valve sensor. Of course, the standard type is low cost and the VAV cost is high, which is suitable for the occasions with high precision.
According to the use status, fume hood can be divided into integral lower open type, floor type, two-sided type, three sided glass type, table type, connected type, and special fume hood designed according to different experimental use needs for radioactivity experiment, synthesis experiment and perchloric acid experiment.