The main function of the Fume hood is the exhaust function. In the chemical laboratory, various harmful gases, odors, moisture and flammable, explosive and Corrosive substance are generated during the 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, there were few Fume hood, Only used in particularly harmful and dangerous gases and experiments that generate a large amount of heat. The Fume hood only serves as the auxiliary function of the test bench. Considering the improvement of 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 functions suitable for the use of equipment. In particular, most new laboratories require air conditioning, so the number of Fume hood to be used should be included in the air conditioning system plan in the preliminary design stage of the building. Since Fume hood occupies a very important position in the biochemical laboratory, the number of Fume hood is increasing by leaps and bounds from the aspects of improving laboratory environment, improving labor hygiene conditions, and improving work efficiency. Subsequently, ventilation ducts, piping, wiring, and exhaust have become important topics in laboratory construction.

The main purpose of using the Fume hood is to discharge the harmful gas generated in the experiment and protect the health of the experimental personnel, that is, to have a high degree of safety and superior operability, which requires that the Fume hood should have the following functions:

(1) Release function: It shall have a 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 shall have the function of non backflow of harmful gas into the room from the inside of the Fume hood by the airflow generated by the exhaust fan. In order to ensure the realization of this function, it is a good method to connect a Fume hood and a ventilator with a single pipe, which can not be connected with a single pipe, but only can be connected in parallel in the same room on the same floor. The ventilator should be installed at the end of the pipe (or at the top of the floor) as far as possible.

(3) Isolation function: the front of the Fume hood shall be equipped with a non sliding glass window to separate the inside and outside of the Fume hood.

(4) Supplementary function: It shall have a channel or an alternative device for drawing air from outside the Fume hood when discharging harmful gases.

(5) Wind speed control function: in order to prevent harmful gases from 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 Air changes per hour. The main focus is on the experimental content and the properties of harmful substances. Generally, the standard for non-toxic pollutants is 0.25-0.38m/s, for toxic or hazardous substances is 0.4-0.5m/s, for highly toxic or slightly radioactive substances is 0.5-0.6m/s, for gaseous substances is 0.5m/s, and for granular substances is 1m/s. To ensure such wind speed, the exhaust fan should have the necessary static pressure, which is the frictional resistance of air when passing through the ventilation duct. When determining the wind speed, attention must also be paid to the issue of noise. When air flows through the pipeline, it is limited to 7-10m, and exceeding 10m will generate noise. Usually, the noise limit for the laboratory (indoor background noise level) is 70dBA. Increasing the cross-sectional area of the pipeline will reduce the wind speed, thus reducing noise. Considering the funding and construction issues of the pipeline, it is necessary to carefully select the power of the pipeline and exhaust fan.

(6) Heat resistance and acid and alkali corrosion resistance: some Fume hood need to be equipped with electric furnaces, and some experiments produce a large number of toxic and harmful gases such as acid and alkali, which are extremely corrosive. The table top, lining plate, side plate of the Fume hood and the selected water nozzle and air nozzle shall have anti-corrosion function. When strong acids such as sulfuric acid, nitric acid and hydrofluoric acid are used in the semiconductor industry or corrosive experiments, it is also required that the overall material of the Fume hood must be acid and alkali resistant and must be made of stainless steel or PVC.

category

According to the use status, Fume hood can be classified into integral lower open type, floor type, two side type, three side glass type, table type, integrated type, as well as special Fume hood designed for radioactive experiment, synthetic experiment and perchloric acid experiment according to the use needs of different experiments.

Safety is the Great Commission of Fume hood. The use of Fume hood in laboratory is to ensure the safety of users and prevent pollution to the surrounding environment.

These security measures are mainly reflected in

1. Adopting a single seam exhaust structure, effectively discharging harmful gases.

2. A streamlined handle with a gap between the handle and the glass ensures effective air intake from the surface due to the rotational flow of air on the countertop.

3. Set up anti drop pins for the window, in case the steel wire rope falls off and the glass window accidentally falls, the anti drop pin will catch it to prevent injury to personnel.

4. The glass windows are made of tempered glass, so even if the glass is accidentally damaged or exploded, there will be no injuries.

5. The upper part of the Fume hood is provided with a vent hole, so that air can enter even if the glass window is closed to avoid greater negative pressure.

6. The shell of Fume hood is made of metal material, which is fireproof and incombustible. The inner cavity is made of flame-retardant or non combustible materials such as anti magnification plate and stainless steel plate. The countertop is made of solid core physicochemical plate or stainless steel plate, which is acid alkali resistant, heat resistant, and flame retardant.

7. The effective height of the glass window is 800mm, the inner cavity is 1200mm, and the height of the countertop is 800mm, which is ergonomic, easy to operate, has a large usage space, and improves safety.

8. The water nozzle and air nozzle are equipped with remote operating handles outside the cabinet, which is more convenient and safe than direct manual operation.

Pay attention to safety when using Fume hood

◆ Before the experiment, it must be confirmed that the Fume hood should be in operation state before the experiment can be carried out.

Before the end of the experiment, it is necessary to continue running for at least 5 minutes before turning off the ventilation fan to exhaust the residual gas in the pipeline. It is also possible to consider installing an exhaust time delay device to ensure delayed operation of the ventilation fan.

During the experiment, do not place any equipment within 150mm of the glass window. Large experimental equipment should have sufficient space and should not affect the flow of air. The front window should be closed for use as much as possible.