There are three types of hoods in use at Case Western Reserve University:
Fume hoods are an engineering control to protect personnel from hazardous fumes. Laminar Flow Hoods protect materials from contamination. Like fume hoods, biological safety cabinets provide protection for personnel, but focusing on biological rather than chemical agents. Class II and III biological safety cabinets also provide product protection. For detailed information about fume hood monitors see poster 1 and poster 2.
For information on bio-hoods, see Selection Use and Installation of Biosafety Cabinets-CDC 2007.
For our department's policy on bio cabinet/hood certification, see EHS Policy on BSC Certification.
Biological Safety Cabinet Certification Form
The importance of proper certification cannot be emphasized enough since persons who manipulate infectious microorganisms are at increased risk of acquiring an occupational illness when their BSCs are functioning improperly.
Centers for Disease Control (CDC), Primary Containment for Biohazards
Biological Safety Cabinets must be inspected and certified by a trained technician annually. The EHS office contracts with Laboratory Certification Services, Inc. (LCS) to certify all BSCs on campus. The cost of certification is the laboratory's responsibility.
In order to schedule a certification please complete the Biological Safety Cabinet certification form.
If the laboratory is moving all BSCs must be decommissioned by a certified technician. See our section on laboratory equipment disposal and relocation.
Chemical fume hoods are designed to provide protection to researchers from chemicals and radiological exposure. Any toxic or volatile (tendency of a chemical to vaporize) chemical must be used inside of a chemical fume hood to lower the chances of inhalation exposure.
The following work practices should be used to maximize the effectiveness of a chemical fume hood.
- Ensure that your chemical hood has a current inspection sticker (dated within the last 365 days).
- Verify that the chemical hood is drawing air. Check the flow monitor (if present) or use a "Kimwipe" to demonstrate flow into the hood.
- Use sashes to maximize protective shielding and ventilation
- Vertical sashes should be lifted sashes only as far as needed to do your work comfortably. Under no circumstances should the sash be lifted above the most current certification label.
- For hoods equipped with horizontal sashes, slide the sashes to minimize the openings, keeping a panel between you and your work.
- Perform all work and keep all apparatus at least six inches into the hood. Performing work at least six inches inside the hood will help prevent disruptive air currents from developing at the hood face.
- Discontinue work if the flow alarm sounds during use. Inform the EHS office of the condition of the chemical fume hood.
- Perchloric acid should not be heated in a chemical hood unless it is specifically designated as a “Perchloric Acid Hood”.
- Chemicals, including hazardous waste, should not be stored nor allowed to evaporate inside the hood.
- Keep chemical hood sashes closed when the hood is not in use.
- Never put your head in the hood when chemical are in the hood or experiments are in progress.
- Route service connections under the airfoil. Electrical cords, tubing from compressed gas cylinders, etc should be under the airfoil to prevent disruption in airflow and allow the sash to be closed completely.
- Slots in the hood baffle should be free of obstructions and air allowed to flow freely inside chemical fume hood. Objects inside hood should be kept at least six inches from all edges of the chemical fume hood.
To report a problem with a fume hood, or to request certification, please go to Report Chemical Fume Hood Issues.
For more information about regarding using your chemical fume hood safely, see our Chemical Fume Hoods PowerPoint.
Laminar Flow Hoods
Laminar Flow Hoods provide protection to samples by directing clean air toward the research or out of hood. This prevents any contaminated air from entering the laminar flow hood and contaminating samples. Laminar flow hoods must never be used when working with any infectious material or volatile/toxic chemicals.
Biological Safety Cabinets (BSCs)
Choosing the proper BSC for your laboratory can be a difficult process. Protection of personnel and research samples, as well as the cost of equipment and annual certification are just a few factors which should be taken into account. The following information is to be used as a guide to help you choose the appropriate equipment for your laboratory.
Types of BSCs
BSCs provides personnel and environmental protection, but no product protection. Class I hoods can be either hard-ducted into a building exhaust system or allowed to circulate air back into the room. With both situations, a high-efficiency particulate arrestance (HEPA) filter is in place to provide protection to the environment. Users are protected by inward airflow.
Class II (types A1, A2, B1, and B2)
BSCs provide personnel, environmental and product protection. Users are protected by inward airflow while a downward laminar flow of HEPA-filtered air provides product along the work surface of the cabinet. Air exhaust is passed through a certified exhaust HEPA filter which removes all contaminant. This air may be recirculated back into the laboratory (Type A) or exhausted out of the building.
- Type A1: 70 percent recirculated, 30 percent exhausted to a common plenum. In order to prevent the buildup of chemical vapors in the room, volatile chemicals must not be used.
- Type A2: Similar to type A1, but with a negative rather than positive pressure plenum. Type B3 has been replaced by a type A2-hard ducted to the building’s exhaust.
- Type B1: Designed for manipulations of minute quantities of hazardous chemicals with in vitro biological systems. This system does recirculate 30% of exhaust back into room so extremely volatile chemicals must not be used.
- Type B2: System provides both biological and chemical protection by providing total external exhaust. Please note that some chemicals have the ability to degrade the HEPA filter causing a loss of containment.
Provides maximum protection to the environment and the worker and should be used when working with microbiological agents assigned to biosafety level 4.
|Type||Face velocity (lfpm)||Airflow Pattern||Radionuclides/Toxic Chemicals||Biosafety Level(s)||Product Protection|
|Class I* open front||75||In at front; rear and top through HEPA filter||No||2, 3||No|
|Class II Type A||75||70% recirculated through HEPA; exhaust through HEPA||No||2, 3||Yes|
|Type B1||100||30% recirculated through HEPA; exhaust via HEPA and hard ducted||Yes (low levels/volatility)||2, 3||Yes|
|Type B2||100||No recirculation; total exhaust via HEPA and hard ducted||Yes||2, 3||Yes|
|Type B3||100||Same as IIA, but plena under negative pressure to room and exhaust air is ducted||Yes||2, 3||Yes|
|Class III||N/A||Supply air inlets and exhaust through 2 HEPA filters||Yes||3, 4||Yes|
* Glove panels may be added and will increase face velocity to 150 lfpm; gloves may be added with an inlet air pressure release that will allow work with chemicals/radionuclides.