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A fume hood is laboratory equipment that protects scientists from negative effects of experiments by keeping air inside the hood. Fume hoods have physical characteristics, and there are two main types: recirculation and range hoods. They provide protection from hazardous gases and have built-in features to make experimentation easier. An alternative is a fume arm, which is more mobile and compact and is often found in academic laboratories.
A fume hood is laboratory equipment that is used to protect scientists from the possible negative effects of an experiment. This is mainly done by keeping the air inside the hood away from the people doing the experiment. Fume cupboards also offer other features and protections that are useful in a laboratory environment.
Fume cupboards have distinct physical characteristics. The base of the range hood usually has the appearance of a typical laboratory bench and may have built-in storage, above the floor. Above and connected to the bench is a very large enclosure called a closet. The cabinet will have a movable door, or sash, on the front that can be raised or lowered to allow access to the worktop portion of the hood. The openings along the edges of the worktop and/or in the upper part of the cabinet allow the evacuation of gases inside the cabinet. The experiments are performed inside the cabinet with the door as low as possible in order to protect the experimenters.
Fume hoods are of two main types: recirculation and fume hoods. A recirculating hood draws the air around an experiment into a built-in filter, then releases the purified air into the lab or cabinet. A fan built into the cabinet is usually the main extractor in a recirculating hood. A range hood has air drawn out of it and into a ventilation system, where it is cleaned and then released outside the building. There are usually several extractor hoods connected to such a ventilation system.
Fume cupboards provide protection from more than just hazardous gases. The enclosed nature of the cabinet helps protect experimenters from being injured 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.
Most fume cupboards have numerous built-in features to make experimentation easier. The vapor-sealed lights allow experimenters to see what they are doing. Electrical outlets both inside and outside the hood are common and allow for easy use of electronic devices during the experiment. Vacuum pumps are also common and allow experiments to be conducted at low pressure or under vacuum. Gas outlets that can be connected to various tanks and streams are useful for specific experiments, as are water taps and drains.
An alternative to a fume hood is a device called a fume arm. Also known as mouthpiece vacuum cleaners, these long tube-like devices can be placed on experiments in an open laboratory environment to suck out any hazardous gases. In a laboratory that is equipped with it, there are usually multiple extraction arms, almost always connected to a central ventilation system or an air purifier. Extraction arms are much more mobile and compact than fume hoods and also cost much less. They have many uses, but are most often found in academic laboratories where many experiments are performed simultaneously on long lab benches.
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