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Fume Hood Basics
A chemical fume hood is a partially enclosed work space that is exhausted to the outside. When used properly, hazardous gases and vapors generated inside the hood are captured before they enter the breathing zone. This serves to minimize your exposure to airborne contaminants. The common parts of a fume hood and their major functions are:
Hood Body -- The visible part of the fume hood that serves to contain hazardous gases and vapors.
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.
Sash -- By using the sash to adjust the front opening, air flow across the hood can be adjusted to the point where capture of contaminants is maximized. Each hood is marked with the optimum sash configuration. The sash should be held in this position when work involving the fume hood is being performed and closed completely when the hood is not in use.
Airfoil -- Found along the bottom and side edges airfoils streamline air flow 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.
Work surface -- Generally a laboratory bench top, but also the floor of a walk-in hood, this is the area under the hood where apparatus is placed for use.
Exhaust plenum -- An important engineering feature, the exhaust plenum helps to distribute air flow 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 air flow and uneven performance.
Face -- The imaginary plane running between the bottom of the sash to the work surface. Hood face velocity is measured across this plane.
