Comparing Ductless vs Ducted Fume Hoods

Many laboratory applications require the use of fume hoods to trap and exhaust volatile vapors and hazardous gases.Fume hood design has come a long way in the past few decades and there are several different types to choose from.Traditional ducted fume hoods are connected to the facility ductwork to send contaminated air out of the facility.Ductless fume hoods are self-contained units that filter contaminated air and recirculate clean air back into the room.Both types of fume hoods have advantages and disadvantages in terms of cost, availability and other factors, it is important to evaluate these factors before purchasing.

Factors to consider when selecting the ideal fume hood

While ductless fume hoods offer several advantages they are not suitable for all applications.“Industry safety standards require that a detailed chemical assessment be completed prior to implementing these products,” explains Luke Savage,Ventilation Technical Director at Labconco. “If you are unsure whether your application and chemical usage will remain the same, or if your application has not been approved by the filter supplier of the ductless hood manufacturer, you will need to address these issues beforehand.” Another key consideration for ductless fume hoods, Savage adds, is the expected filter life and your organization’s tolerance for changing filters at that frequency."Estimated filter life information is always provided in the range hood manufacturer's filter evaluation," says Savage. From a practical standpoint, since ductless fume hoods do not need to be connected to ductwork, they are more flexible in terms of placement and can even be moved to different locations as needed.If environmental concerns are a top concern, a ductless model may be a better choice.While some ducted fume hoods contain filters, others do not and send unfiltered contaminated air out of the facility.Depending on the application and the fumes generated, this may have a negative impact on the environment. Ductless fume hoods trap contaminants in filters that are often disposed of in landfills.

Weighing the costs of each option 

Purchasing a fume hood can represent a substantial capital investment, so it is important to carefully consider the costs involved. While ducted units tend to be less expensive than ductless models, unit cost isn't the only thing to keep in mind.At a minimum, the installation of a ducted fume hood will involve connection to the existing facility ductwork.“Many existing laboratories will have capacity in their existing infrastructure in the form of heating,cooling and ventilation capacity to support ducted enclosure supply and exhaust airflow needs,”Savage explained. "However, if this is not present, the cost of adding it will certainly exceed the initial cost of the fume hood itself.”In addition to initial installation, you'll also need to consider ongoing costs, depending on which model you choose. Savage points out that with the ducted model, in addition to the initial cost of the hood and mechanical support system, there are significant ongoing operating costs of tempering and moving the air.Operating costs for ductless devices are much lower.As Savage explains, "The air is simply drawn out and recirculated back into the lab, unlike a ducted hood where it's drawn from the outside, tempered, brought into the lab, passed through a range hood, and sent back outside.”