Laminar Flow or Ductless – How to Select the Right Type of Fume Hood

Fume Hoods Play a Critical Role in Preventing Exposure to Chemicals, Particulates, and Other Risks in Laboratory Research and Product Manufacturing

If you are designing or upgrading a laboratory facility, providing a safe, secure place for your laboratory research team is a top concern. State-of-the-art fume hoods, — if designed properly and used sensibly —  can protect workers by significantly reducing unnecessary exposure to toxic chemicals and radioactive materials. They can also help prevent particulate contamination in clean room environments.



Fume Hood Designs Vary Significantly Based on the Type of Hazardous Substance Used

It would be easy if there were a universal fume hood design that could handle any type of hazardous substance that you threw at it — unfortunately, that’s not the case.

That’s because fume hood designs are closely related to the specific types of hazardous substances that they can handle. This makes it especially important to set down some parameters during the design stage to identify which classes of materials that your lab can or cannot handle — now and in the future.


Comparison of Ductless Fume Hood Designs versus Laminar Flow Hoods

Traditional laminar flow fume hoods have ducting that vents the air from the hood area to outside vertical stacks. Depending on the compounds being used, it may be further filtered and/or treated. The exhaust is then dispersed, in very low concentrations, into the atmosphere.


The laminar flow approach has some disadvantages:

First, laminar flow fume hoods remove a large amount of air from the laboratory, which must be replaced by new temperature controlled air supplied by the HVAC system. This can be expensive from an energy use perspective – these types of fume hoods have been known to drive your electricity bills through the roof.

Second, it’s not possible to move laminar flow hoods around to different locations easily. They are tied to extensive ductwork systems — and typically filtration and treatment systems as well — laminar flow hoods cannot be moved without extensive renovations. Foresight and planning ahead are paramount in the design stage.


Ductless fume hoods are a primary alternative option.

ductless-fume-hoodsIn this type of fume hood, the air is treated within the unit using extensive filtering systems — typically incorporating some form of activated charcoal filtration. The treated air is then returned to the laboratory. This ductless design overcomes the two main objections of laminar flow hoods: Because the air is returned, there is less drain on the HVAC system for a lower energy cost, and ductless systems can be moved around within a laboratory relatively easily as they are not dependent on ducts mounted through the walls. They also typically plug into standard 110 or 220-volt outlet boxes. Placed on top of a Formaspace Basix with casters, the move is further simplified.


However, ductless systems have their own set of disadvantages:

Ductless systems can only be used when the chemicals passed through it are known quantities and are approved for use with the filtration system. For example, ammonia and carbon monoxide gasses will easily pass through a standard activated carbon filter. This means that each and every chemical compound that could be used in a ductless system needs to be certified to match the filtration capabilities of the system you use. Because of these limitations, ductless systems are excluded for use in experiments or processes which could produce unknown results which could evade treatment by the type of ductless filtration system in use.

There are other disadvantages as well. Ductless fume hoods require the use of expensive filters that must be replaced at regular intervals — if this is not done correctly, it will pose a significant risk to lab personnel. Noise is also another potential disadvantage — since the filtration fan unit is built into the unit.



Comparison of Advantages and Disadvantages of
Ductless Fume Hoods versus Laminar Flow Fume Hoods

Ductless Fume Hoods



Not attached to fixed ductwork Only specific chemicals and processes can be used
Less energy cost Not suitable for experiments with unknown outcomes
Easily moved around lab Loud fan noises
Contaminated air is contained in filter system Risk to personnel if filtration system not maintained

Laminar Flow Fume Hoods



More suitable for use in experiments with unknown outcomes Requires extensive ductwork installation
Can be used with a wider range of compounds and processes Uses significant amount of energy (HVAC) to replace treated air
Less risk of contamination inside the building Generally, fumes are ducted to the atmosphere rather than treated
Typically less noisy than self-contained ductless systems Difficult to reconfigure laboratory to a new floor plan without extensive work



Formaspace Can Provide You with an Unlimited Range of Specialty Fume Hood Designs for Your Unique Application

In addition to the general purpose laminar flow and ductless fume hoods discussed above, Formaspace can also provide specialty fume hood designs that handle specific types of materials or processes.


Low bench fumehoodLow-Bench Fume Hoods

Many Formaspace customers looking for a general fume extraction solution choose the so-called Low-Bench design. Because it sits directly on a low height Formaspace workbench (18” off the ground), it’s easy to coordinate this fume hood with other matching design elements, such as Formaspace work tables, storage units, wet sinks, and more.


Perchloric Acid Fume Hoods

Working with Perchloric acid can result in a dangerous residue build-up of perchloric acid crystals, which are an explosion risk. Fume hoods designed for this application have built-in washing systems to eliminate the risk.


Acid Digestion Fume Hoods

High acid concentrations can damage work surfaces in the fume hood; using Polypropylene or PTFE (Teflon) coated surfaces will resist the acid. It may also be necessary to replace the traditional glass material in the fume hood door (called the sash) with transparent material made of polycarbonate, which resists acid etching more effectively than glass.


Internal Wash Fume Hoods

Like Perchloric acid fume hoods, other chemical compounds can build up on the inside of surfaces. Fume hoods with built-in wash systems can clean the internal surfaces to prevent damage caused by the accumulation of chemical compounds.


Scrubber Fume Hoods

The exhaust waste from many chemical substances can be treated via an ionizing scrubbing system. The exhaust air is passed through a series of filter elements which chemically bind to the chemicals, trapping it so that it can be disposed of as solid waste.


Radioisotope Fume Hoods

If you are working with radioactive compounds, then you need a fume hood with built-in protection from radiation — typically in the form of heavy lead bricks lining the walls — that is encased in a protective stainless steel case.


Need to Speak with an Expert on Fume Hood Applications? Call Formaspace.


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Do you have questions about specialty fume hood designs that handle specific types of materials or processes? Want to order a fume hood for your unique application?

Visit the fume hood section of our website to learn more.

Then talk to our experts.

Our Formaspace Design consultants will recommend the exact type of fume hood you need for your laboratory or manufacturing facility.


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