Laboratory Fume Hoods
Lab Tops • Lab Hoods • Lab EquipmentFume hoods, also known as chemical hoods, are one of the most necessary safety devices in any laboratory, because they minimize chemical exposure to research workers, and protect workers from inhaling hazardous vapors. Basically, a fume hood comprises a hood and a sash, which can be opened or closed to regulate air flow. There are many types of fume hoods, each designed with a particular application or function in mind. Traditional fume hoods (CAV and VAV), benchtop fume hoods, and ductless fume hoods all serve certain purposes, and are installed depending upon the lab's use.
Traditional hoods are designed for general protection, and have a constant air volume (CAV). These types of hoods can be installed with or without a bypass provision, which is an additional opening for air supply into the hood.
An alternative to the CAV hood is the variable air volume hood (VAV), which can vary the air volume exhausted through the hood depending upon sash position. The benefit of this type of hood is that it eliminates excess face velocity, which can lead to contaminated air that endangers the scientist.
Benchtop fume hoods are smaller, economical fume hoods that are ideal for small facilities, or for facilities that require lots of fume hoods, such as schools, colleges, and universities.
Ductless fume hoods have conventional design but are self-contained to re-circulate air into the lab after filtration occurs.
Other specialty lab exhaust systems include walk-in hoods, which allow for large pieces of furniture; "snorkels," which are somewhat mobile and allow the worker to place it over the area needing ventilation; canopy hoods, which are used for exhausting particularly large areas; and glove boxes, which are used when the toxicity of the substance being used is too great to be used with a fume hood.
Using Your Fume HoodIf your lab is on a college campus, the Office of Environment, Health & Safety should check your fume hoods every six months to make sure the air velocity is within the correct range. However, you'll still want to take protective measures.
First of all, adjust the sash to make sure that there are adequate airflow velocities at the work opening. Adjusting the sash correctly will also protect you against splashes and debris.
Next, you'll want to make sure the fume hood is in good working order before you begin. How do you do this? Well, the law states that all hoods must have some sort of visual indicator that tells the user whether it is working or not. Older models may have something quite simple, like a piece of tissue or a ribbon attached to the sash. Newer models often have alarms and pressure gauges. If there is no indicator, tape something to the sash, such as a piece of paper or a ribbon. If the fume hood is working correctly, it will be drawn into the hood.
Fume Hood Information Resources
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Laboratory Fume Hoods