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Ducted Versus Ductless Fume Hoods

Modern safety and eco-friendly features make ductless fume hoods a suitable option for some labs

Andy Tay, PhD

Ductless fume hoods can offer unique advantages compared to traditional fume hoods, including being a more cost-efficient option that requires no ductwork. Additionally, temperature-controlled air is not removed from the workplace, which may contribute to energy savings. Contaminated air is also not expelled into the environment. 

Here, we will discuss recent innovations and features in ductless fume hoods.

Filters

Some institutions do not allow recirculated air from fume hoods to enter the rest of the lab facility as experiments may generate hazardous gases. However, manufacturers have innovated to ensure that ductless fume hoods are safe to use with minimal risks. One way they have achieved this is by introducing more powerful filters. Filtration in ductless fume hoods usually occurs in two steps. The first is pre-filtration using foam to remove large particles. This is followed by main filtration such as using activated carbon or high efficiency particulate air (HEPA) filters to remove organic odors and noxious vapors. Depending on the applications, additional filters can also be installed to remove compounds like formaldehyde and ammonia that cannot be removed by activated carbon or HEPA filters. The advantage of a ductless fume hood is that it is a plug-and-play system where users can customize the types of filters depending on their experimental needs.

Monitoring for safety and energy efficiency

Another desirable feature of a ductless fume hood is monitoring. Manufacturers have started introducing features for users to remotely check the type of filter installed, the length of time installed, and degree of filter saturation, which indicates time to change a new filter. Fume hoods continuously remove large volumes of temperature-controlled air from lab spaces, resulting in the large consumption of energy. One of the more significant innovations is the variable air volume (VAV) fume hood design that varies the volume of room air exhausted, such as using damper or valve-based on sash position. The use of VAV fume hoods, together with policies to reduce sash height, has been shown to lead to significant cost savings in electricity bills by multiple universities. VAV hoods also offer enhanced safety as they are electronically connected to the hood exhaust and air supply in the building. This connection can alert users to unsafe hood-airflow conditions. Many newer fume hoods also include a user interface where users can digitally control the sash levels to maximize safety and protect samples.

Portability and customizability

One of the disadvantages of a ducted fume hood is that it’s bulky and connects to an exhaust pipe that expels air from the unit into the atmosphere. If the exhaust pipe is damaged, there will be significant lab work interruption. Ducted fume hoods also require more time to install.

On the other hand, there are plenty of options for portable ductless fume hoods that can be easily relocated and configured into different sizes to suit the needs of users. Most ducted fume hoods are low and have a vertical sliding sash. However, with a ductless fume hood, users can create a taller work zone to set up and accommodate taller lab accessories. Ductless fume hoods can also be equipped with a horizontal sliding sash to accommodate a diverse range of users. Additionally, users may add an epoxy worktop that is acid- and base-resistant to improve shelf life of the fume hood or an antibacterial coating to eliminate contamination.

Although ductless fume hood technology is relatively well-established, manufacturers are still trying to find ways to improve its safety, user-friendliness, and energy efficiency. Users can consider these factors when determining if a ductless fume hood can meet their scientific needs and enhance research productivity.