Specifications of Fume Hood
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.
