Choosing a fume hood can seem like a daunting task. There are so many options to choose from and so much information to gather in order to make an informed decision. But fear not, help is at hand! First, spend a few minutes answering these questions. When you have answered all seven questions, you have successfully established the criteria necessary for choosing a fume hood system. Second, review the answers with the Application Specialist and we will make product recommendations based on your answers.
- 1. What will you be doing inside the hood? Try to document as much as you can about the application. What chemicals are used, and how are they used? Is heat involved? What volumes of chemicals will be used at a given time? Most importantly, know the answers to the following three questions:
2. What size fume hood do you need? This is a three-part question. Part one is, “How wide do you want the fume hood?” Labconco offers fume hoods from 30" wide to 16 ft wide, and many options in between. Part two is, “What, if any, equipment needs to be enclosed in the hood?” If you do have equipment, what are the dimensions? This information is essential to determining how deep the hood needs to be to house your equipment. Lastly, do you need a bench-top or floor mounted hood.1. Do you use Perchloric Acid?
2. Do you use Hydrofluoric Acid (HF)?
3. Are you working with Radioisotopes and require the use of Lead Bricks?
- 3. What, if any, service fixtures are needed? These include (but are not limited to) airflow monitors, electrical outlets, compressed air, laboratory gas, vacuum, and water. Gooseneck faucets are also available. Finally, do the fixtures need to be factory installed, or will the installer handle that?
- 4. What accessories are needed? Do you need a work surface and base cabinets, or will you use existing casework to support the hood? If you do need base cabinets, do you need acid storage, solvent storage, or nonchemical storage? Do you need ductwork from the hood to the roof, or will your HVAC contractor provide it?
- 5. How will the fume hood be exhausted? Will there be a dedicated blower (exhaust fan) for this hood, or will it connect to a central system? If it connects to a central system, will it be constant volume or variable volume? If you need a blower, proceed to question 6.
- 6. Do you need a built-in blower or a remotely located blower? Built-in blowers are easier (and therefore less expensive) to install, but they can be noisy and put the ductwork under positive pressure, so should not be used with toxic applications. Built-in blowers are also limited to smaller hoods with short, straight duct runs. Remote blowers, though more complex to install, can be sized for the specific situation and put the ductwork under negative pressure for safer operation. If a remotely located blower is needed, proceed to question 7.
7. What is the layout of the duct run? Will the duct go directly to the roof, or does it need to make some turns before reaching the roof? What diameter of duct will be used? Once the duct penetrates the roof, a final 90º elbow will be needed to turn the duct horizontal, then 3 to 5 ft of straight duct is needed between the elbow and blower. Finally, the exhaust stack should include a zero-pressure weather cap (not a gooseneck, china hat, or mushroom cap), and should terminate at least 10 ft above the roof line to allow the fumes to get up into the airstream and not be returned into the building’s air handling equipment.
Refence source: http://www.coleparmer.com/TechLibraryArticle/1359
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