A laboratory fume hoods is a local ventilation device whose main purpose is to limit exposure to toxic fumes like dust or vapors. In this ventilated enclosure, vapors, gases, and fumes are trapped and eliminated from the work area.
Types of fume hoods
Fume hoods come in two basic types as listed below:
- Constant volume: In this type, the quantity of air pulled or the exhaust flow rate is constant. When you lower the sash, the hood opening area decreases, and the airflow velocity increases proportionally. Hence, you can increase the velocity of air by lowering the sash.
- Variable air volume: This is where the exhaust flow rate varies when the sash is raised or lowered to maintain an even face velocity. So, when the sash is lowered, the hood’s cross-sectional area decreases with the airflow velocity remaining constant and minimizing the total air volume exhausted.
Size of fume hoods
Laboratory fume hoods are available in different sizes: 1000mm, 1200mm, 1500mm, 1800mm, and 2000mm. The depth ranges between 1900mm and 2700mm.
What are fume hoods made of?
Fume hoods are made of the following linear materials:
- Phenolic resin
- Epoxy resin
- Fiber-reinforced plastic
- Cement board
- Square-corner stainless steel
- Covered-corner stainless steel
- Polypropylene
Functions of the control panel in fume hoods
Most fume hoods are embedded in a mains-powered control panel. They perform the following functions:
- Notify when the airflow is low
- Warn when there is a large opening at the front of the unit
- Giving permission to switch the exhaust fan on or off
- Giving consent to turn the internal light on or off.
Functioning of fume hoods
Generally, a fume hood is equipped with an interior baffle and a movable front sash. It is on the design to determine which direction the sash will move. The sash may move horizontally, vertically, or a blending of the two. The sash gives protection to the user by serving as a barrier between the experiment and the worker.
The hood has slots and baffles that direct the air. In many hoods, you get the provision to adjust these slots and baffles from getting blocked. Mostly, the blockage is caused by excessive material storage. If there is a blockage, the exhaust path within the hood gets affected and thereby lessening the efficiency of hood capture.
Use of fume hoods
The purpose of using fume hoods is very clear. Besides protecting the user from inhaling toxic gases, it also protects the item or experiment. Moreover, it is a sustainable approach as fume hoods protect the environment. The non-core functions of fume hoods include spill containment and explosion protection.
How are fume hoods installed?
Generally, fume hoods are installed against the walls and are fitted with infills to combat the exhaust ductwork. Due to their recessed shape, they are poorly illuminated by general lighting. So, many fume hoods comprise internal lights with vapor-proof covers. The front side of the fume hood is a sash window, mostly made of glass that can move up and down on a counterbalance mechanism.
Fume hoods are extensively used in the laboratory as a primary method of exposure control. Researchers should use fume hoods while operating with toxic compounds with a boiling point below 120oC. This laboratory equipment is of great help to scientists and researchers as it prevents them from getting exposed to harmful substances or chemicals.
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