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What's that Sticker on My Fume Hood Anyway?

Fume hoods are important and critical pieces of equipment in many labs, and a competent certification company can align the operator, the laboratory environment and the hood itself to improve effective hood use.

by Jim Sigler
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A Reputable Certification Company Trains Personnel, Tracks Service and Certification Dates, and Performs Appropriate Tests

Many pieces of lab equipment lend themselves to proper operation. A freezer, for example: Close the door and it will generally perform as expected. And, like most lab equipment, it is linked to the facility in a simple way—through the power cord (and sometimes through an alarm wire).

“Hoods” are important and critical pieces of equipment in many labs, but they don’t lend themselves to proper operation. Biosafety cabinets, chemical fume hoods and laminar flow benches are easy to operate improperly, and they are susceptible to subtle factors in the laboratory environment.

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The “sweet spot” for effective hood use is found at the intersection of three elements: (1) the operator and how he/she interacts with the hood; (2) the laboratory environment and how it impacts the hood; and (3) the hood itself.

The operator

The operator is critical to the effective operation of the hood.
It is the operator who has responsibility for turning on the unit, setting the window height and following the procedures for proper hood operation. For the different types of hoods, these procedures include:

Biosafety Cabinet: The operator should follow aseptic procedures, sanitizing materials just prior to placing them in the BSC, maintaining good techniques (changing gloves as needed, not placing hands above open media or plates) and not placing sterile items on the front grate.

Chemical Fume Hood:The operator should promote good air flow by putting larger items (equipment, vessels) up on stands or blocks, and should avoid significant clutter. Hoods in active use should not be used for storage of chemicals or waste.

Laminar Flow Bench:As with the BSC, the operator must follow aseptic procedures, sanitizing materials prior to placing them in the unit and not placing hands upstream of the sterile product. Laminar flow benches can be either horizontal or vertical—neither protects the operator, only the product. Be sure to distinguish between a BSC and a vertical laminar flow bench, as they can look similar but still have very different uses.

The environment

The environment in which the hood operates cannot be overlooked as a critical factor in proper hood operation. The most frequent environmental cause of a hood not performing as expected is the laboratory’s HVAC system. Something as simple as the air supply for the lab can be a problem—air blowing onto or across the front of a hood can disrupt the airflow, which is critical to proper operation. Another factor that can affect proper hood operation, specifically exhausted hoods (chemical fume hoods and Type B2 BSCs), is insufficient air supply to the lab. Insufficient air supply can literally “choke off ” the hoods, rendering them less effective. This can be due to a design flaw (not enough air supply in the first place), a lack of integration of the various control systems or because something has changed since the lab was built (most commonly, units having been added).

The hood itself

Above all, the unit must be operating correctly. Determining whether the hood is functioning as designed is the goal of the certification process. The units are tested at the factory, upon installation, and then periodically (typically annually in a research setting) throughout their life cycles. The hoods are also tested after they have been moved and after significant maintenance (filter changes, etc.).

The three tables below describe the purpose of each type of hood or cabinet, review the approach to field certification and provide an overview of the most common types of failure. 

Biological Safety Cabinet (BSC)

Chemical Fume Hood

Laminar Flow Bench

The BSC tests described above are considered secondary tests. The primary tests include items such as the pressureleak test and are required in order to qualify for NSF listing (but are not typically performed in the field).

Choosing a certification company

Good certification is about good service. A reputable certification company will do all the following: 1) send technicians who are uniformed, courteous and able to work comfortably and unobtrusively in a laboratory environment; 2) keep track of your equipment and service due dates, notifying you of upcoming certifications; and 3) perform all appropriate tests. If the technician takes less than 20 minutes to test each BSC, be wary. A good technician comes with a cart full of test gear, not a briefcase!

Beyond the mechanics of hood certification, your certification company can be an important resource. Good certification companies can help you determine what type(s) of hoods are appropriate for your needs as they grow or change. They are able to answer questions about proper usage of your hoods. And they will quickly repair your hood when it is not functioning properly.

Don’t hire a certification company that doesn’t promise to do all the above. And while most of the certification companies out there will promise to do all these things and will deliver, inevitably there will be a few “bad apples” (as in any industry) who don’t deliver. Be vigilant, get to know your certifier and ask questions until you are satisfied that you are getting the services you are paying for and that good laboratory practices demand.


Proper operation of your hoods depends on your personnel, your facility and the hoods themselves. Field certification confirms that the hoods are operating as designed. A good certification company will competently perform that testing and can also be a resource to help ensure that your personnel are properly trained and your facility is properly configured.