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. Wasting air by forcibly removing it is the most significant ongoing cost of fume hood operation—greater than the cost of acquiring and installing a hood, and much greater than the hood’s operating costs.
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. Yet low flow is by no means universally acknowledged as an improvement. Alvin Heath, director of business development at ESCO Technologies (Hatboro, PA), says low-flow hoods “challenge the traditional concept that higher inflow equates with better containment. Convincing end users to work with these hoods is an uphill task.”
Some notable features available on modern fume hoods include: improved ergonomics, making them easier to work in for long periods; “intelligent” sashes, which close when a motion sensor detects no movement in front of the hood for a given time period, reducing energy consumption; improved hood baffle designs, to allow for best airflow navigation; and digital airflow monitors, which can alert personnel when problems arise. Perhaps the most striking development is the ductless fume hood, which recycles conditioned air.
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 Alvin Heath, director of business development at ESCO Technologies (Hatboro, PA). 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
UniFlow SE Constant Volume
• Features a unitized flame-retardant composite resin construction for chemical and corrosion resistance
• Angled picture-framed sash opening has an aerodynamic air foil for uniform air flow entry into the fume chamber
• Surfaces are glass smooth for ease of cleaning with excellent reflectivity
HEMCO
www.HEMCOcorp.com
Protector XStream
• Available in 4’, 5’, 6’ and 8’ sizes
• Operates at a broad range of face velocities from 60 to 1,000 fpm
• Sash handle, air foil, upper dilution air supply and rear downflow baffle contribute to horizontal airflow patterns to reduce concentrations of contaminants
Labconco
www.labconco.com
Mobile EDU Ductless
• Completely self-contained and provides all around visibility
• Features a Multi-Layered EDU Filter with 99.9% filtration efficiency
• Base is mounted in large heavy-duty wheels for ease of transport
•Exceeds OSHA, ANSI, BSI and AFNOR Safety Standards
Air Science USA
www.airscience.com
Purair Advanced Ductless
• Face velocity at 100 fpm ensures containment of fumes
• An alarm will alert the operator when the airflow falls to an unacceptable level
• The work area features a removable spillage tray which can be easily cleaned
•Main filter can be chosen from 14 different types of carbon
Air Science USA
www.airscience.com
