Exhaust air systems  Manufacturers, Traders, Suppliers

A fume hood is typically a large piece of equipment enclosing five sides of a work area, the bottom of which is most commonly located at a standing work height.
Two main types exist, ducted and recirculating (ductless). The principle is the same for both types: air is drawn in from the front (open) side of the cabinet, and either expelled outside the building or made safe through filtration and fed back into the room. This is used to:
protect the user from inhaling toxic gases (fume hoods, biosafety cabinets, glove boxes)
protect the product or experiment (biosafety cabinets, glove boxes)
protect the environment (recirculating fume hoods, certain biosafety cabinets, and any other type when fitted with appropriate filters in the exhaust airstream)
Secondary functions of these devices may include explosion protection, spill containment, and other functions necessary to the work being done within the device.
Fume hoods are generally set back against the walls and are often fitted with infills above, to cover up the exhaust ductwork. Because of their recessed shape they are generally poorly illuminated by general room lighting, so many have internal lights with vapor-proof covers. The front is a sash window, usually in glass, able to move up and down on a counterbalance mechanism. On educational versions, the sides and sometimes the back of the unit are also glass, so that several pupils can look into a fume hood at once. Low air flow alarm control panels are common.
Fume hoods are generally available in 5 different widths; 1000 mm, 1200 mm, 1500 mm, 1800 mm and 2000 mm.[1] The depth varies between 700 mm and 900 mm, and the height between 1900 mm and 2700 mm. These designs can accommodate from one to three operators.

1. Hood Body
The visible part of the fume hood that serves to contain hazardous gases and vapors.
2. Baffles
Moveable partitions used to create slotted openings along the back of the hood body. Baffles keep the airflow uniform across the hood opening, thus eliminating dead spots and optimizing capture efficiency.
3. Sash
The sliding “door” to the hood. By using the sash to adjust the front opening, airflow across the hood can be adjusted to the point where capture of contaminants is maximized. Each hood has its optimum sash configuration. The sash should be held in this position when working in the hood and closed completely when the hood is not in use. The sash may be opened completely to set up equipment, but must be returned to the optimum setting prior to generating contaminants inside the hood.
Hoods are equipped with one of three types of sashes:
• Vertical
Vertical sashes provide the greatest overall access and are the most common.
• Horizontal
Horizontal sashes provide the best access to the top interior of the hood, but do not provide access to the entire width at the same time. However, they can be positioned as a body shield to protect the operator, while enabling access through the sides.
• Combination vertical and horizontal
Combination sashes combine horizontal sash panes, in a vertical rising frame. As such, they offer the advantages of both vertical and horizontal sashes.
4. Airfoil
Located along the bottom and side edges the airfoil streamlines airflow into the hood, preventing the creation of turbulent eddies that can carry vapors out of the hood. The space below the bottom airfoil provides source of room air for the hood to exhaust when the sash is fully closed. Removing the airfoil can cause turbulence and loss of containment.
5. Work surface
Generally a laboratory bench top, or the floor in the case of a floor-mounted hood, this is the area where the work is conducted.
6. exhaust plenum
The exhaust plenum helps distribute airflow evenly across the hood face. Materials such as paper towels drawn into the plenum can create turbulence in this part of the hood, resulting in areas of poor airflow and uneven performance.
7. Face
The imaginary plane between the bottom of the sash and the work surface. Hood face velocity is measured across this plane.

Medical, physical, biological, chemical, biochemical area
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