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Chemical fume hood guide for laboratory designers.

 
scientist working at a fume hood A properly functioning fume hood is one of the most important pieces of laboratory safety equipment.  A chemical fume hood can protect workers from inhaling chemical fumes by constantly pulling contaminated air into the hood and exhausting it out of the building.  It can also protect users in case of a fire or explosion by helping to physically contain the event.

A conventional fume hood is designed with an adjustable sash that can be raised and lowered in front of the user's face.  These traditional fume hoods use constant air volume (CAV) exhaust fans, which exhaust air from the hood at a constant rate, regardless of sash height.  This simple design can result in unacceptably high air velocities at the face of the fume hood when the front sash is lowered and nearly closed.

The most common fume hood is the constant volume conventional hood.  This hood is enclosed on three sides, and has a sash that slides in the front.  The sash can go up or down, which determines the hood's performance and face velocity.

chemical fume hood A conventional bypass fume hood is an improved design, featuring a protected, secondary air intake above the sash face area.  This air intake gradually opens as the sash is lowered, thereby limiting the velocity of air flowing under the sash into the hood.  This allows for a consistent removal of air from the lab.

A constant volume auxiliary air hood allows outside air — also called "auxiliary air," to come in directly in front of the sash, but outside the hood.  This auxiliary air is different than the air in the room.  These types of hoods are most often used in laboratories that don't have a quantity of room air sufficient for the operation of the fume hoods.

A radioisotope hood is a type of constant volume air hood that is designed for ease of cleaning.  Because they are often used with radioactive materials, the liners are designed so they can't be penetrated by these materials, and the base is strong enough to support heavy shielding bricks.  Special HEPA air filters are used on these hoods to collect radioactive material.

A variable air volume (VAV) fume hood can sense the sash position, and adjust the volume of air exhausted through the hood accordingly.  These fume hoods can virtually eliminate the excess face velocity and air turbulence problems associated with CAV hoods.  These hoods are generally quite energy-efficient.

fume hood in a pharmaceutical laboratory In some situations, where environmental concerns or government regulations dictate, ductless fume hoods or fume hood scrubbers may be appropriate or required.

  • A ductless fume hood often incorporates replaceable charcoal and HEPA filters to remove a variety of air contaminants around a laboratory workstation, and release the cleaner exhausted air indoors.  These aren't connected to any exhaust system, but are designed to absorb certain chemical fumes.
  • A fume hood scrubber reduces the emission of water soluble vapors and contaminants into the atmosphere by intercepting them with a liquid spray.  Perchloric acid hoods come equipped with sprayers that wash away accumulated matter.

Other specialized types of fume hoods include distillation hoods, canopy hoods, downdraft hoods, and elephant trunks.

  • A distillation hood is any kind of general hood that has a greater interior height, so that it may accommodate larger apparatuses.  A California hood is a type of distillation hood that has either vertical or horizontal sashes in the front and back.  Another type of distillation hood is the walk-in hood, which is mounted on the floor and allows for large objects or equipment to be placed inside.
  • When heat and steam needs to be drawn away, canopy hoods, which can be placed over large pieces of equipment like ovens, are frequently used.  Slot hoods draw air via slots in their side walls, and are frequently used with sinks.
  • Downdraft hoods are a popular choice when it comes to exhausting heavy materials, such as powder or dust.  These particles are drawn through a perforated surface and then exhausted.
  • Elephant trunks are flexible ducts designed to catch discharge from instruments that produce vapors or odors.

Laboratory fume hoods are often the primary control device when using toxic and flammable chemicals in a laboratory.  It is important for lab personnel to understand how chemical fume hoods operate so they can use them correctly and avoid undue exposure to hazardous materials.

A Laboratory Technician Conducts an Experiment in a Fume Hood

When designing a laboratory hood system, it is important to consider the application and operating conditions as well as air flow requirements, environmental regulations, and maintenance issues.

The size of the hood will usually depend upon the size of the workspace.  The most common hood sizes range from 3 to 6 feet wide, but specialized fume hoods can be up to 8 feet wide.  Custom-sized hoods are also available.  The hood sash, and whether it opens horizontally, vertically, or both, will also depend on the use of the fume hood.  Hood linings vary according to what kind of chemicals and other substances they will be exposed to.

Because the whole purpose of the hood is to ensure that operators are safe from chemicals and other contaminants, the correct fume hoods must be used according to specifications.  There are different fume hoods for different situations, and using a sub-optimal fume hood can negate the reason for using it in the first place.

This laboratory hoods page provides another perspective on fume hood designs and applications.

Fume Hoods Consultants and Suppliers

  • Hanson Lab Hoods
    This California-based firm offers walk-in and benchtop fume hoods that feature quality construction and innovative design.
    www.HansonLab.com
  • Longo Fume Hoods
    This New Jersey-based laboratory design and planning firm offers expertise in fume hood design, installation, and support services.
    www.LongoLabs.com
  • HEMCO Corporation
    This Missouri-based laboratory solutions firm distributes UniFlow laboratory fume hoods and accessories.
    www.HemcoCorp.com

Fume Hood Manufacturers

  • Labscape
    This laboratory products company offers a broad spectrum of chemical fume hoods and modular casework, including a good selection of quick-ship items.
    www.Labscape.com
  • Kewaunee Scientific Corporation
    This designer and manufacturer of laboratory products features a series of fume hoods and a guide to fume hood selection.
    www.Kewaunee.com
  • BMC
    This Michigan-based firm is a manufacturer of quality laboratory casework, fume hoods and accessories.
    www.BMCLab.com
  • AirClean Systems
    This supplier of fume containment solutions specializes in application solutions for the laboratory environment.  They manufacture a series of ductless fume hoods and laminar flow hoods designed to protect lab workers from toxic vapors, gases, fumes and particles.
    www.AirCleanSystems.com
  • Air Master Systems
    Air Master manufactures chemical fume hoods and stainless steel casework for industrial, clinical healthcare, educational, and r&d markets.
    www.AirMasterSystems.com
  • Hamilton Lab - Fume Hoods
    This Wisconsin firm offers an extensive selection of standard and custom fume hood products.
    www.HamiltonLab.com
  • LabCrafters
    This New York-based firm designs and manufactures steel and stainless steel casework, furniture, and fume hoods for the laboratory industry.
    www.Lab-Crafters.com
  • Labconco
    This laboratory equipment manufacturer features a line of fume hoods and enclosures, biological safety cabinets, HEPA filtered enclosures, and carbon-filtered enclosures.
    www.Labconco.com
  • FumeHood.net
    Laboratory Equipment Manufacturers (LEM) manufactures quality laboratory products including the "Eliminator" line of laboratory fume hoods for the laboratory and chemical fume hood industry.
    www.FumeHood.net
  • Terra Universal - Hoods
    Terra manufactures a comprehensive line of exhaust fume hoods, including benchtop and free-standing models.  Options include HEPA/ULPA filtration modules, chemical vapor filters, ionizers and air flow meters.
    www.TerraUniversal.com
  • Mott Manufacturing
    This Canadian firm offers fume hoods that are developed to meet the demanding safety, energy conservation, and operational requirements of the modern laboratory.
    www.Mott.ca
  • Jamestown Metal Products
    This New York-based casework manufacturer is a premier maker of painted and steel furniture and equipment solutions for the laboratory, education and government markets.
    www.Jamestown.com
  • Sheldon Laboratories
    Sheldon fume hoods, recommended for school science lab use, are designed to remove fumes and manage airflow safely and efficiently.
    www.SheldonLabs.com
  • Genie Scientific - Fume Hoods
    Genie manufactures several types of fume hood for laboratory ventilation applications.
    www.GenieScientific.com
  • Lab Fabricators
    This Ohio-based firm designs and manufactures bench fume hoods and walk-in fume hoods as well as distillation and specialty hoods.
    www.LabFabricators.com
  • Hawkins Scientific
    This California company offers custom laboratory fume hoods and laboratory ventilation systems.
    www.HawkinsSci.net

Fume Hood Resources

  • Laboratory Chemical Hood User's Guide
    This extensive article about chemical fume hoods includes information concerning their uses, safe operating procedures, design styles, and function monitoring.  Published by the Department of Environmental Health & Safety at the University of Louisville.
    www.Louisville.edu
  • Fume Hoods Fact Sheet (pdf)
    Overview of fume hood safety issues including how and when to use a laboratory hood.  Published by the Office of Environment, Health & Safety at UC Berkeley.
    www.EHS.Berkeley.edu
  • Laboratory Fume Hood Energy Calculator
    This energy calculator is published by the Lawrence Berkeley National Laboratory.
    www.LBL.gov

Related Laboratory Resources


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