Lab Manager Magazine's Independent Guide to Purchasing a Fume Hood
Purchasing the correct fume hood for your laboratory is a very important, long-term decision and your choice in lab ventilation systems will affect future lab planning, flexibility and safety. This guide will introduce the four main fume hood types available. Read about each one and then proceed to LabWrench.com to check out all the latest models.
In the past, were the only option available to labs and account for only one component of a total lab ventilation system, which includes a series of ducts, blowers and filters running through the entire building. However, choosing the right fume hood enclosure for inside your lab space is very important.
Conventional Ducted Fume Hoods often describes the traditional, less elaborate fume hoods that have a constant air volume. Face velocity is inversely proportional to the sash height unless a by-pass is in place. The by-pass helps direct airflow and reduces the increase in face velocity as the sash closes. The by-pass enables the hood to have a more constant volume of exhaust air. This provides general protection to the lab worker.
Variable Air Volume Ducted Fume Hoods maintain a constant face velocity regardless of the sash position by employing a closed loop system that is constantly measuring and adjusting the amount of air being exhausted. In many hoods, inaccurate face velocities will sound audible and visual alarms, which in addition to the constant face velocity, greatly increase the protection of the lab worker. This also reduces the total volume of supply and exhaust air needed, which in turn lowers total energy costs.
Canopy Ducted Fume Hoods are typically used when the area that needs ventilation is too large to fit inside a regular hood. They are suspended above the work area. The lab worker is not protected well, as the fumes are often drawn right across the user’s breathing zone.
Ductless Fume Hoods are single enclosed units that require no duct work or fixed installation. They remove fumes, vapors and particles from both the experiment and the lab worker by filtering them through a combination of HEPA and carbon filters and exhausting them safely back into the lab air.
Benchtop Ductless Fume Hoods offer a very convenient alternative to traditional ducted fume hoods as they can be placed on rolling carts and moved around the lab as required, or permanently mounted to a bench. The lab worker is protected as the fumes are drawn back, up and away while clean air is recirculated back into the lab after being filtered.
Down Flow Workstations direct air in the opposite direction as most other hoods; they push it down. The air containing powders or chemicals with high molecular weights are swept into the base of the workstation, protecting the lab worker by removing it away from their breathing zone.
Portable Ductless Fume Hoods are designed to go anywhere science takes you in the field or for temporary hood needs in the lab. The lab worker is protected as the fumes are drawn back, up and away while clean air is recirculated back into the environment after being filtered.
Biological Safety Cabinets provide effective containment for lab workers working with human pathogens. There are three separate classes of BSC’s available: Class I, II and III; some with additional sub-class levels. These classes are designated by the National Sanitation Foundation.
Class I Biological Safety Cabinets have an un-recirculated airflow away from the lab worker that, after going through a HEPA filter, is vented into the atmosphere. They provide the lab worker adequate protection but do not protect the samples in the cabinet from contamination.
Class II Biological Safety Cabinets are used when working with microorganisms in containment levels 2, 3 and 4 labs. They are divided into two types, A and B, determined by their construction, airflow velocities, patterns and exhaust systems. They protect the lab worker, samples and the external environment.
Class III Biological Safety Cabinets have both HEPA-filtered supply and exhaust air and are totally enclosed and gas tight while work is performed using long-sleeved gloves. The cabinet is kept under negative pressure of at least 120 Pa while an exterior exhaust system maintains airflow. This protects the lab worker, the samples and the external environment.
Laminar Flow Hoods provide clean air via a HEPA filter to the lab bench space and a constant air flow out of the work area, which prevents surrounding room air from entering. The air flowing out of the hood also suspends and removes contaminants and particles creating clean air spaces.
Horizontal Laminar Flow Hoods bring in external air through a pre-filter, and HEPA filter then push it in horizontal lines outward from the back of the hood workspace. While this protects the samples from particle contamination, these hoods are not intended to protect the lab worker.
Vertical Laminar Flow Hoods move air down from the top of the unit in a vertical line through a HEPA filter to the bottom intake. A blower then pushes the air back up to a HEPA filter exhaust. While this protects the samples from particle contamination, these hoods are not intended to protect the lab worker.
PCR Enclosures are designed specifically to provide a Class 5 work space for PCR experiments by moving HEPA filtered air downward. What makes them unique is a UV light that eliminates DNA and RNA contaminants.
Fume Hood Sponsors:
A tradition of safety and performance. The Baker Company has pioneered the design and manufacture of biological safety cabinets, clean benches, and fume hoods for almost sixty years. In fact, The Baker Company created the world’s first clean air work station in 1951, the SterilSHIELD®. Since then, The Baker Company has been at the forefront of engineering reliable contamination control equipment. Although the technology has advanced through the years, Baker’s uncompromising commitment to quality, testing, and workmanship has never wavered. This legacy, along with a valued partnership with customers, has built a lifetime of trust around the Baker name. www.bakerco.com
Thermo Scientific technologies are backed by our global commitment to provide the safest and most reliable biological safety cabinets and fume hoods available. We deliver unmatched quality and world-renowned service and support. Our newest product designs minimize costs of operation and maintenance and maximize comfort and convenience for advanced ease of use. They are compliant with the most stringent regulatory standards in the world that ensure your safety. www.thermo.com
MISONIX AURA Portable Ductless Fume Hoods have been the quality leader in the market for 40 years. The new design AURA 30, AURA 42, AURA 54 features ASHRAE Certification, UL Listing, Filter Performance verified by FTIR. The MISONIX 3-2-1 Warranty, Filtrak filter locking system and new full width sash openings compliment the powder coated aluminum chassis and head section and offer a quiet, truly portable solution that will provide years of reliable performance and service. Our in house chemical engineers will evaluate your application free of charge. "When you only want to buy it once, buy MISONIX". www.misonix.com
New from NuAire, the CellGard ES NU-480 Class II, Type A2 Biological Safety Cabinet utilizes DC ECM motor technology ensuring a low total cost of ownership. Over-sized HEPA filters with more filter media equal longer filter life; HEPEX Zero Leak Airflow System and an optimally determined forward-curved fan reduce noise and vibration. TouchLink Electronic Control System monitors, displays, and controls real-time airflow. The Ergonomic design reduces fatigue; front hinged panel opens 30° for increased cleanibility, along with DECON-101, NuAire’s exclusive decontamination kit. CellGard ES provide long-term reliability; outstanding performance; superior quality; with cost saving technologies. www.nuaire.com