Commodity, Lab Appliances, but Strong on Innovation
It would be difficult to imagine a chemistry laboratory without at least one fume hood. Despite their ubiquity and the notion that they are not “sexy” lab products, a great deal of innovation has occurred in fume hoods during the last decade.
Fume hoods are connected to a building’s heating, ventilating, and air conditioning (HVAC) system, which removes air through the hood’s front panel. Vented air ultimately comes from the lab’s working area. It is expensive to heat and cool work-space air, says Jon Zboralski, director of air-flow products at Thermo Fisher Scientific (Two Rivers, WI). Wasting air by forcibly removing it is the most significant ongoing cost of fume hood operation—greater, eventually, than the cost of acquiring and installing a hood, and much greater than the fume hood’s operating costs.
Luke Savage, a sales engineer at Labconco (Kansas City, MO), describes conventional fume hood designs as “huge energy hogs.”
About ten years ago, the industry introduced the first low-flow fume hoods, which operated at lower face velocities than did traditional hoods. The standard used to be about 100 cfm; low-flow systems vent toxic gases just as well at 60 cfm, a 40 percent energy savings. Typical lab air entails costs of about $5/cfm/yr, so a typical old-style hood costs about $5,000- $6,000 per year to operate.
Low-flow systems are designed to operate at 60 cfm at all sash positions. “You get great savings, even with the sash fully raised, but even better savings with the sash closed,” Savage says.
Yet low flow is by no means universally acknowledged as an improvement. According to Alvin Heath, director of business development at ESCO Technologies (Hatboro, PA), low-flow (which he calls “high-containment, lowflow”) hoods “challenge the traditional concept that higher inflow equates with better containment. Convincing end users to work with these hoods is an uphill task,” even when gas-containment tests prove low flow’s mettle.
Resistance is particularly high in highly competitive, low-margin analytical labs with an installed base of old-style hoods. “And some folks still wonder whether low flow is a good thing to do. It’s been quite a battle between the facilities people and the environmental health experts,” Zboralski tells Lab Manager.
Ergonomics, “smart” sashes, and air recycling
Fume hood manufacturers have incorporated other interesting innovations as well. Today’s hoods have an expanded viewing area and an improved counterbalance system that assists in raising and lowering the glass window. Thermo Fisher, for example, has adopted advanced chain-and-socket mechanisms to make the counterbalance more reliable. “A good cable and pulley used to last for about 100,000 cycles,” Zboralski says. “Today the chain-andsprocket systems are still going strong after 250,000 cycles. All the major players have adopted this system.”
Fume hood vendors have also finally addressed ergonomics, an important consideration, since many organic chemists practically “live” inside their hoods. Hood entrances are now slanted back, rather than outward, which makes them easier to work in for long periods. Sash designs have also improved, and some units now feature horizontal sliding panels.
Another interesting development is the “intelligent sash,” which closes when a motion sensor detects no movement in front of the hood for a specified time period, for example, when the operator walks away. This feature alone can reduce energy consumption by 70 percent, according to Savage.
Hood baffle designs have also undergone significant improvements, says Heath. “Baffles are cleverly angled, and nowadays even perforated, to allow for best airflow navigation to the exit point; that is, to reduce airflow residence time in the hood as much as possible.” Today’s baffles are also easily removed for cleaning, which prolongs the service lifetime of the hood.
Digital airflow monitors, which are reasonably priced, provide real-time diagnostics of the hood’s extraction performance and can alert building maintenance when problems arise.
Perhaps the most striking recent development has been the introduction of ductless fume hoods. Instead of venting to the environment, ductless hoods use filtration systems that recycle conditioned air.
Early variations of the recycling idea worked fine, but the charcoal filters were less than optimal for some important fumes, and users were slow to replace the filters. “There was a lot of resistance to these devices,” Zboralski says.
Then Erlab (Rowley, MA), a Thermo Fisher partner, designed a charcoal material that removes and retains a much broader base of reagents. The new designs are unlikely to replace all vented fume hoods any time soon, but they can easily serve about 10 percent of installations today, according to Zboralski. “And as time goes by that number will grow,” he adds.
Users should be aware of problems that may crop up during specification and installation of fume hoods. Most new fume hood purchases are for new laboratories, according to Heath. Traditionally, laboratory furniture suppliers provide the fume hoods as well. Although a few manufacture hoods that are standards-compliant, Heath says, “many still construct fume hoods as though they were simple boxes. Fume hood prices are often bundled with furniture prices, and that makes it difficult for the end user to make informed decisions.”
Heath provides the following wish list for potential fume hood buyers:
- Local installation and support for ducting, controller, and exhaust blower
- Appropriate safety certifications
- Construction materials for specific application, for example, polymer inner liners for corrosive acids, ceramic work tops for high temperatures
- Local references for the supplier/ installer
- Aesthetics and cost
For additional resources on fume hoods, including useful articles and a list of manufacturers, visit www.labmanager.com/fume-hoods
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