The fume hood is one of the essential laboratory furniture. It plays the role of exhaust and air exchange in the laboratory.
The structure of the fume hood is up and down type, its top has exhaust holes, can be installed fan.
The upper cabinet has a deflector plate, circuit control touch switch, power socket, etc. The see-through window is made of toughened glass, which can be moved left and right or up and down. For human operation.
The lower cabinet adopts the style of experimental side table, above the countertop, below the cabinet. The countertop can be installed with small water cups and faucets.
The material of the fume hood is made of various kinds of materials, such as all-steel, steel-wood, all-wood, aluminum-wood, plastic-steel, PVC structure, etc. Its countertop is the place which is in direct contact with the operator, and it is made of solid-core physicochemical board, stainless steel board, PVC, ceramics and other materials.
Old fume hoods are mostly made of wood, but modern ones are mostly made of steel coated with epoxy resin. Common cabinet width of 1000, 1200, 1500, 1800 and 2000 millimeters several specifications, 700-900 millimeters deep, 1900-2400 millimeters high. They can be used by 1-3 people at the same time. Fume cupboards are usually installed against the wall.
In the center of the front is a transparent door (mostly glass) that can be moved up and down, and the opening height is usually 100-600 mm. Behind the door for the experiments carried out on the work surface, there are water pipes, sewers, power supply, vacuum pumps, air pipelines and other experiments need to be connected, on the light with a protective cover lighting. Air is extracted by the exhaust fan above the front of the cabinet, or led elsewhere through the pipeline (called full ventilation), or filtered and re-circulated (become ductless ventilation).
Most fume hoods will sound an alarm to alert the operator when (1) the exhaust volume is too small (2) the front glass door is opened too far, and generally the wind speed at the operating port should not be less than 0.5m/s after the glass door is opened all the way, and there are switches to adjust the speed of the exhaust fan and the light inside.
When using the person standing or sitting in front of the cabinet, the glass door will be lowered as far as possible, the hand through the door under the cabinet into the experiment. Since the exhaust fan draws air inward through the open door, no harmful gases will overflow in large quantities under normal conditions.
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Fume hood concept
Laboratory ventilation is an integral part of laboratory design. In order to keep laboratory workers from inhaling or swallowing some toxic, pathogenic or toxicity of unknown chemicals and organisms, the laboratory should be well ventilated. In order to prevent the absorption of some vapors, gases and particles (smoke, soot, dust and air suspension), pollutants must be removed by fume hoods, fume hoods or local ventilation.
The fume hood is the most commonly used in the laboratory, a local exhaust equipment, a wide variety of types, due to its different structure, the use of different conditions, its exhaust effect is not the same. The performance of the fume hood good ring, mainly depends on the speed of air movement through the fume hood.
Classification of fume hoods
Fume hoods are classified according to the way of exhaust:
They are divided into three categories: upper exhaust, lower exhaust, and upper and lower exhaust at the same time. In order to ensure that the working area of the wind speed is uniform, for the cold process of the fume cupboard should be used in the lower exhaust type, for the hot process of the fume cupboard using the upper exhaust type, for the process of unstable heat, can be set up in the upper and lower exhaust with the changes in the cabinet heat to adjust the upper and lower exhaust proportion, so as to get a uniform wind speed.
The fume hood is classified according to the way of air intake:
Full-exhaust fume hood: through the indoor air intake in the cabinet cycle and then discharged to the outdoor known as the full-exhaust type, which is a very widely used type.
Complementary air fume hood: when the fume hood is set up in the heating or temperature and humidity control requirements of the room, in order to save heating, air-conditioning energy consumption, the use of air from the outdoor take the complementary wind in the cabinet cycle and then discharged to the outdoors is called the complementary air fume hood.
Variable air volume type fume hood: ordinary fixed air volume system requires manual adjustment of fixed blade dampers, adjusting the fume hood's exhaust air volume, when adjusting the valve to a certain angle to achieve the desired surface wind speed. Variable air volume control is by adjusting the valve sensor to change the air volume to achieve a given surface air velocity, of course, the standard type of low-cost, variable air volume cost is high, suitable for occasions requiring high precision.
Fume hoods are categorized according to the state of use:
They can be divided into the whole type of lower open type, floor type, two-side type, three-side glass type, table type, one-piece type, and according to the needs of different experiments and the design of the radioactivity experiments, synthetic experiments, and perchloric acid experiments on the special fume hoods.