What is the principle of fume hood ventilation? What are the types of fume hoods?

The ductless SEGE-fume hood does not require external ducts, does not pollute the external environment, and has little impact on the laboratory temperature. However, the disadvantage is that the filter material must be changed regularly, the experimenter is more likely to be exposed to harmful gases than if using an exhaust fume hood, and because the extra exhaust fan is very close to the experimenter, it will cause noise.

This type of fume hood has the following filtration process: dust removal with foam plastic front filtration, and activated carbon filtration, which adsorbs off many chemicals. However, ammonia and carbon monoxide require other special filtration devices to remove them.

The pre-filtered material can be used for an average of 6 months, and the activated carbon layer can be used for an average of 2 years, but the specific life depends on the use.

A fully ventilated fume hood draws the air from the cabinet elsewhere and dissipates it into the atmosphere after proper treatment. These fume hoods are more effective at removing harmful gases from the laboratory than ductless ventilation, are less noisy, and are easy to maintain. The disadvantage is that special exhaust ducts need to be installed, which may prevent the laboratory from maintaining a constant temperature in the case of different indoor and outdoor temperatures, and it is not good for environmental hygiene.

Common sense of life must be understood, please know.

Self-cleaning fume hood is a kind of fume hood without external pipes, it is an environmentally friendly fume hood, the harmful gases generated by laboratory operations and the harmful gases generated when storing chemicals can be directly filtered through the activated carbon filter, and the clean air is returned to the room after filtration. This technology has been used since 1968 and is the first of its kind in ductless filtration technology.

Common fume hoods are divided into spare categories:1. Exhaust fume hoodAfter circulating in the cabinet through the indoor air intake, it is called full exhaust type, which is a type that is very widely used.

2. Make-up fume hoodWhen the fume hood is set up in a room with heating or temperature and humidity control requirements, in order to save heating and air conditioning energy consumption, the method of taking the supply air from the outside and circulating it in the cabinet and discharging it outside is called a crack filling high-air fume hood.

3. Variable air volume type to talk about the source of the fume cabinetThe ordinary constant air volume system needs to manually adjust the damper with fixed blades, adjust the exhaust air volume of the fume hood, and reach the desired ground wind speed when adjusting the valve to a certain angle. Variable air volume control is to change the air volume to achieve a given surface wind speed by adjusting the sensor of the valve, of course, the standard type has low cost and high variable air volume cost, and is suitable for occasions that require high accuracy.

How many kinds of laboratory furniture --- fume hoods commonly used in the laboratory are there to distinguish the vertical from the material, including all-steel fume hoods, PP fume hoods, stainless steel fume hoods, steel and wood fume hoods, FRP fume hoods and other jujube closed sources.

In terms of function, there are standard fume hoods, desktop fume hoods, walk-in fume hoods (floor fume hoods), down-suction fume hoods (lower exhaust fume hoods), conjoined fume hoods, etc.

When a fume hood is installed in a room with heating or control requirements for temperature and humidity, in order to save heating and air conditioning energy consumption, the method of exhausting air from the outside and circulating it in the cabinet and then expelling it to the outside is called a supplemental air fume hood.

The other is a variable air volume controlled fume hood.

Ordinary exhaust airflow systems require manual adjustment of the damper with fixed blades, adjustment of the exhaust airflow of the fume hood, and the required surface air velocity is achieved when the valve stool door is adjusted to a certain angle. Variable air volume control is to change the air volume through the sensors of the regulating valve to achieve a given surface wind speed. Of course, the cost of the standard type is very low.

Variable airflow is costly and is suitable for applications that require high precision.

Fume hoods are used in laboratories to ensure the safety of users and to prevent contamination of the surrounding environment.

1. Before the start of the experiment, it must be confirmed that the fume hood should be run before the experiment.

2. At least 5 minutes or more before the end of the experiment, the fan can be turned off to expel the residual gas from the pipe. It is also possible to envisage installing an exhaust time delay to ensure fan delay.

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

Fume hood. According to the way of exhaust tomb, it is divided into three categories: upper exhaust type, lower exhaust type and upper and lower exhaust type.

According to the use state, the fume hood can be divided into integral lower open type, dusty and floor-to-ceiling type, two-sided type, three-sided glass type, desktop type, and conjoined type.

According to the material, the fume hood is divided into all-steel, stainless steel, PP fume hood, commonly used ones, as well as organic and inorganic, etc., mainly in structure, material, exhaust classification.

1. Check before operation.

The operator can start using the fume hood after activating the roof fan system, and should inspect the fume hood before using it

1. Whether the power switch is in the open position.

2. Whether the fluorescent light switch is turned on.

3. Whether the fume hood is in the exhaust state.

When all the test results are in order, the fume hood can be operated.

Second, the correct operation mode of the fume hood.

1. The fully open state of the glass window is only allowed to appear when assembling and debugging internal instruments and equipment or cleaning the space in the cabinet, which is the "debugging state".

2. Adjust the glass window to open to the user's elbow (half-open), so that the operator's hand reaches into the cabinet to operate the experiment, and the chest above is protected by the glass window safety tempered glass, which is the "normal operation state".

3. Adjust the door to open to the lowest opening, and the operator leaves, so that the experimental program in the cabinet reacts or pauses the experiment by itself, which is the "standby state".

4. When the experimenter is in the fume hood experiment, he should avoid sticking his head into the adjustment door to avoid danger.

5. Avoid placing too many non-essential items and equipment in the fume hood, so as not to interfere with the normal flow of air and cause disturbance (turbulence).

6. During the experiment and after the completion of the fume hood door, do not pull too high.

7. Before finishing the work and leaving the fume hood, the operator should turn off the power supply of the equipment in the fume hood, turn off all the water, electricity and gas switches, and reduce the adjustment door to the lowest position before leaving.

8. Although the fume hood is made of polymer corrosion-resistant materials, proper cleaning and maintenance is necessary to prolong the service life. If there are reagents and drugs splashed during ordinary use, they should be wiped and removed immediately, and the inside should be wiped clean with clean water before stopping work every day and leaving, and the deflector should be removed for cleaning and inspection at least once every three months.

9. The cabinet under the fume hood is equipped with a power control box, so it is strictly forbidden to place any corrosive substances, nor can the power control box be blocked, so as to avoid danger. 10. Each fume hood has a circuit protection system (dual protection of thermal relay + AC contactor), and a circuit breaker (NFB) for the total power supply (with leakage protection) is set up to control and protect the fan, damper, lamp and socket. The power socket only provides 10A 220V specifications, and when the total power consumption of the equipment exceeds 10A, it needs to be designed separately.

The following points should be noted under the proper use of the fume hood:

1. When the fume hood is in use, make up air for 10 minutes every 2 hours (i.e., open the window for ventilation); If the use time is more than 5 hours, open the window and pay attention to avoid negative pressure in the room.

2. The laboratory should also be ventilated from time to time when the fume hood is not in use, which is beneficial to the health of the test personnel;

3. When more than 2 fume hoods use 1 fan, in order to avoid operation errors or impropriety, the "on" and "off" of the fan can only be controlled by 1 operator; If another fume hood is not in use or is to be discontinued, an air volume control valve can be used to close the vent; Avoid repeating "on" and "off" the fan repeatedly, which not only damages the life of the fan, but also makes the experiment inaccurate.

4. When the fume hood is in use, avoid the interference of the countercurrent wind direction caused by the movement of personnel to the fume hood;

5. The indoor air temperature is between -5 and +40, and the average value for 24 hours does not exceed +25;