Many laboratory applications require the use of a fume hood to trap and exhaust volatile vapors and hazardous fumes. Fume hood design has come a long way over the past few decades and there are several different types to choose from. Conventional ducted fume hoods connect to facility ductwork, sending contaminated air outside the facility. Ductless fume hoods are standalone units that filter contaminated air, recirculating clean air back into the room.
Both types of fume hoods have advantages and drawbacks in relation to cost, practicality, and other factors, and it’s important to assess these before making a purchase.
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 the completion of a detailed chemical assessment before implementation of these products,” explains Luke Savage, director of ventilation technologies at Labconco. “If you are not certain that your application and chemical use will remain constant, or if your application has not been approved through a ductless hood manufacturer’s filtration provider, these will need to be addressed before entertaining a ductless hood.”
Savage adds that another key consideration for ductless fume hoods is anticipated filter life and your organization’s tolerance for changing filters at that frequency. “Projected filter life information is always provided in the hood manufacturer’s filter assessment,” says Savage. From a practical standpoint, because ductless fume hoods don’t need to be connected to the ductwork, they are more versatile in terms of placement and can even be moved to different locations if needed.
If environmental concerns are top of mind, a ductless model might be a better option. While some ducted fume hoods contain filters, others don’t and send unfiltered, contaminated air outside the facility. Depending on the specific application and resulting fumes, this could have a negative impact on the environment. Ductless fume hoods trap contaminants in filters, which are typically disposed of in a landfill.
Weighing the costs of each option
Purchasing a fume hood can represent a large capital investment, so it’s important to carefully consider the costs involved. While ducted units tend to be less expensive than ductless models, the unit cost isn’t the only thing to bear in mind. The installation of a ducted fume hood will at least involve connection to existing facility ductwork. “Many existing labs will have capacity in their existing infrastructure in the form of heating, cooling, and ventilation capacity to support the supply and exhaust airflow needs for a ducted hood,” explains Savage. “However, if this does not exist, the cost for adding it will certainly exceed the first cost of the fume hood itself.”
Aside from the initial installation, you also need to look at ongoing costs, which will vary depending on which model you choose. Savage notes that for ducted models, beyond the first cost of the hood and the mechanical support system is the huge ongoing operating cost of tempering and moving the air. The operating cost is significantly less for ductless units. As Savage explains, “air is simply pulled and recirculated back to the lab, unlike a ducted hood where it’s pulled from outside, tempered, introduced to the lab, moved through the hood, and then sent back outside.”