A fume hood is a piece of laboratory equipment that is used to protect scientists from the possible negative effects of an experiment. This is primarily done by keeping the air inside the fume hood away from the people doing the experiment. Fume hoods also offer other features and protections that are useful in a laboratory setting.
Fume hoods have distinct physical characteristics. The base of the fume hood usually looks like a typical lab bench, and may have storage built into it, above the floor. On top of and connected to the bench is a very large enclosure called a cabinet. The cabinet will have a movable door, or sash, on the front that can be raised or lowered to provide access to the worktop portion of the fume hood. Openings around the edges of the worktop and/or at the top of the cabinet allow for the removal of gases in the cabinet. Experiments are performed inside the cabinet with the sash as low as possible so as to protect the experimenters.
Fume hoods provide protection from more than just dangerous gases. The enclosed nature of the cabinet helps to protect experimenters from being hurt by debris if something explodes or splashes. Fume hoods are also usually made of flame-retardant materials, so unexpected fires tend not to be as damaging as they would be in an open area.