Fume Hood Selection Guide

Choosing the right fume hood is critical to ensuring your lab’s safety from hazardous chemicals and vapors. However, the process of researching and purchasing the best lab hood can be a difficult task. 

There are numerous options to consider and a great deal of information to gather in order to make an informed decision. Evaluating the users’ operational and research needs will ensure that the correct type and number of ducted fume hoods are installed in the laboratory—and that your workspace is safe.

In this chemical fume hood selection guide, we will assist you in selecting the best ductless fume hood for your laboratory work environment—to ensure your lab workspace remains as safe as possible.

Keep reading to learn more and find out how a reliable lab furniture supplier can provide your lab environment with the highest quality ductless fume hoods that ensure the safety of your laboratory workspace.

What is a Fume Hood?

A fume hood in a laboratory is a ventilated enclosure where hazardous or toxic fumes or vapors can be safely handled. Its purpose is to capture, contain, and remove contaminants, preventing them from escaping into the laboratory.

This is accomplished by drawing contaminants from the hood’s work area away from the operator, reducing inhalation and contact.

An exhaust blower pulls the air from the laboratory environment through the hood and exhaust system to provide airflow into the exhaust fume hood. Face velocity is measured by the pull at the hood opening.

The air moving into and through the hood is controlled by a baffle, an airfoil, and other aerodynamically designed components.

The contaminated air is then diluted with room air and exhausted to the outside via the hood’s duct system, where it can be dispersed at an acceptable low concentration. Activated carbon filters for the removal of non-hazardous, nuisance odors are also available as laboratory fume hood add-ons.

Types of Laboratory Fume Hoods and Exhaust Hoods

The operational airflow of all laboratory fume hoods can be classified into two types such as the conventional and the by-pass. Variations of the latter hood include high performance, reduced air volume, and auxiliary-air chemical fume hoods.

Let’s examine each of the various types of laboratory fume hoods and exhaust hoods that are available.


The conventional hood is a simple enclosure with an interior baffle and movable front sash but no airfoil. It operates at a constant exhaust volume, with all exhaust air entering the hood through the sash opening.

As a result, closing the sash increases the speed of the air passing through the sash opening, resulting in high face velocities with the sash nearly closed.


The by-pass hood operates at a constant volume and is designed so that when the sash is closed, the air that enters the hood is redistributed, reducing the high-velocity air streams found in conventional fume hoods.

The openings above and below the sash reduce face velocity fluctuations as the sash is raised or lowered. As a result, the face velocity in by-pass fume hoods does not typically reach levels that could be harmful to procedures.


The high-performance hood, a variation of the by-pass hood, is the latest generation of fume hoods that rely on containment-enhancing features to maintain safety while saving energy.

Features of these types of fume hoods include sash stops or horizontal-sliding sashes to restrict sash opening, sash position, airflow sensors to control the opening and closing of mechanical rear baffles, and small fans to introduce air that acts as a barrier in the operator’s breathing zone.


The auxiliary-air hood, a variation of the by-pass hood, provides roughly 50% of the air for the fume hood exhaust from outside the laboratory while limiting the volume of tempered air removed from the laboratory. This hood is also known as induced air, add-air, and make-up air.

Reduced Air Volume

The reduced air volume (RAV) hood is a by-pass hood variation that uses a by-pass block and partially blocks the opening above the sash to reduce the volume of air exhausted and thus conserve energy.

This is used in conjunction with a sash stop, which limits the height at which the sash can be opened during normal use so that the hood requires less air volume to achieve safe velocity.

Variable Air Volume

Variable air volume (VAV) hoods vary the amount of room air exhausted while maintaining a constant face velocity. VAV lab fume hoods change the exhaust volume in a variety of methods.

One approach employs a damper that opens and closes in response to airflow and sash position. Another method is to vary the blower speed to meet air volume requirements, but both methods can be used when multiple hoods share a single exhaust blower.

Perchloric Acid Hoods

Perchloric acid fume hoods are only used with perchloric acid. Organic materials should not be used in a perchloric acid hood because perchloric acid can occur an explosion when it reacts with organic materials.

These chemical fume hoods feature integral work surfaces, radiused interiors, and a drain for easy and thorough cleaning.

Radioisotope Hoods

To facilitate decontamination, radioactive hoods have integral work surfaces and radiused interiors. These hoods should be strong enough to support lead shielding bricks if they are required.

This type of filtered fume hood should also be installed so that high-efficiency particulate air (HEPA) or carbon filters can be used in the ductwork of these filtered fume hoods.

Distillation and Floor-Mounted Hoods

To accommodate large apparatus, distillation and floor-mounted hoods are constructed with extra interior height and depth. Instead of a base cabinet or bench, distillation hoods are typically mounted on a platform.

Let LabTech Supply Company Help You Choose the Right Fume Hood for Your Lab

For over 30 years, LabTech Supply Company has been committed to providing our customers with a comprehensive selection of chemical fume hoods, exhaust fume hoods, filtered fume hoods, and more.

All of our lab furniture is made in the United States, ensuring that our customers receive the highest-quality lab equipment available—while staying within their budget and meeting all industry standards.

If you are in the process of redesigning your lab workspace, learn how we can help you find a perfectly tailored lab furniture solution—regardless of the specific requirements of your lab workspace.

Request a free quote by visiting our website and filling out our online form or contacting us at 800-476-5228 at LabTech Supply Company today!

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