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MindMap: Improving Biological Safety Cabinet and Fume Hood Safety

Indispensible equipment for laboratories, fume hoods and biological safety cabinets (BSCs) protect personnel from exposure to chemicals and pathogens handled during experiments.

John Buie

Indispensible equipment for laboratories, fume hoods and biological safety cabinets (BSCs) protect personnel from exposure to chemicals and pathogens handled during experiments. Fume hoods, or chemical hoods, ventilate the hazardous and noxious chemicals, vapors, gases, or dusts released during experiments.

BSCs, or microbiological safety cabinets, are the primary means to protect laboratory workers and the surrounding environment from pathogens, such as bacteria and viruses. BSCs use high efficiency particulate air (HEPA) filters to remove the harmful pathogens from the air. Most classes of BSCs maintain the sterility of materials being worked with inside.

This MindMap provides the techniques to improve fume hood and BSC safety through training, work practices, and equipment maintenance and certification.

Work practices
Fume hoods and BSCs cannot overcome poor work practices resulting from poor training.

Obtain training in-house or through qualified BSC certifiers, and understand all standard operating procedures before using a fume hood or BSC.

Keep up with new safety requirements and regulations for BSCs
Consult these excellent resources for safety requirements and updates to regulations: Biosafety cabinet certifiers, the Centers for Disease Control, and the National Institutes of Health.

Locate and install fume hoods and BSCs correctly

  • To avoid disturbing the airflow that protects the worker, locate fume hoods and BSCs so lab personnel exiting and entering the lab do not pass in front of them.
  • To protect laboratory personnel, do not install fume hoods directly opposite workstations.
  • Install BSCs to allow access to their supply and exhaust filters for annual certification testing and HEPA filter changes. The top of cabinet must be at least 18” below the ceiling to field test exhaust flow according to NSF Standard 49.

Replace traditional fume hoods with ductless filtering fume hoods
Ductless filtering fume hoods use activated carbon combined with catalysts and neutralizers to filter toxic molecules from the air. They recycle the air directly back into the room, eliminating the dependency on a laboratory’s ventilation system and external ductwork.

Ductless fume hoods—a few drawbacks to consider
Ductless fume hoods are not without limitations. Most carbon-based filters only adsorb specific types of chemicals at low evaporation rates, and so exclude a broad array of chemicals and experiments that produce a large amount of vapors. Ductless fume hoods cannot be used for chemical processes in which two or more chemicals could combine in the filter and react with toxic, exothermic, or explosive properties.

Use new filter technology
New developments in filters, filtration systems, and saturation detectors have eliminated some of the disadvantages of ductless fume hoods.

Versatile filters
New ductless fume hood filters handle acids, bases, and solvents, allowing ductless fume hoods to compete with the capabilities of traditional fume hoods.

Filter saturation detectors
Ductless filtering fume hood filters have limited chemical retention capacity before they saturate and become ineffective. Automatic controllers monitor the carbon filter bed and sample the exhaust air to verify the filters are removing the toxic chemicals to safe limits and alert the user when the filter becomes ineffective.

Advanced filtration systems
Advanced fume hood filtration systems efficiently handle a wider range of chemicals. Systems with modular filtration columns, in which filters for different types of chemical are stacked, easily adapt to multiple chemical types with a simple swap of filters.

Advantages of ductless fume hoods
Ductless filtering fume hoods DO NOT . . .

  • require rooftop exhaust ducts or external blower systems; they recycle the air, saving energy since cooled or heated room air stays in the laboratory.
  • exhaust chemical pollutants or toxic fumes in the atmosphere.
  • limit the location for analyses; they are mobile and allow for multiple or impromptu projects.
  • require lengthy and costly installation.

Fume hoods and BSCs cannot protect lab personnel without scheduled maintenance to keep them operating properly.

Fume hood inspection and periodic maintenance

  • Inspect the fume hood for chemical storage and other blockages.
  • Measure face velocity, complete an airflow visualization test (smoke testing), and conduct a tracer gas containment test (a measure of a fume hood’s containment effectiveness).

Annual fume hood maintenance
Exhaust fan maintenance: Lubricate moving parts, check belt tension, inspect fan blade for deterioration, and record rpm— according to the manufacturer’s recommendations.

HEPA filters
High Efficiency Particulate Air (HEPA) filters, the heart of all classes of BSCs, remove particulates (including microorganisms) from the air. They do not remove vapors or gases. Filter life varies from laboratory to laboratory, but they normally last from 3 to 5 years before needing replacement.

Removing HEPA filters and bag-in/bag-out options
Filters must be decontaminated before removal, typically with formaldehyde gas. Bag-in/bag-out HEPA filter systems provide an option when it is not possible to decontaminate the HEPA filters with formaldehyde gas or when hazardous toxic chemicals have been used in the BSC. These systems come with specially designed seals and puncture resistant bags to enclose the filters before removal.

Where to purchase HEPA filters
Along with BSC manufactures, third-party manufacturers (some with large inventories) sell replacement filters directly.

Set up a performance contract for BSCs
BSC owners should arrange a performance contract with an accredited certifier to maintain their BSC.

Certify and test BSCs
Certify every new BSC to factory standards after installation and completing all plumbing and electrical work. Accredited certifiers field test fume hoods and BSCs to meet manufacturers’ specifications and government standards.

Use remote-controlled equipment
Adjusting settings outside the fume hood on equipment with remote controls, such as hot plates, vacuum pumps, and syringe pumps, eliminates opening the sash and disrupting airflow.

Replace BSCs with new models with improvements in safety, ergonomics, and energy efficiency

Application-specific models
Manufacturers offer fume hoods and BSCs for specific applications, such as weighing, robotics, distillation, filling, and grinding.

Adaptable ergonomics
Height adjustable benches accommodate short and tall workers when sitting or standing.

Computerized network monitoring, user access, and troubleshooting
Laboratory managers and safety officers can now set up a network to monitor multiple fume hoods companyor lab-wide—checking in real time for status information and alarm history, as well as adjusting fume hood settings to conserve energy. Access cards activate all safety protocols for a user’s designated applications and automated calibration functions assist troubleshooting for easy service and fast repairs.

Safety-engineered designs

  • Valves for gas, air, and vacuum located externally eliminate reaching into the fume hood.
  • Access ports route vacuum tubing and cables through the side wall of the biological safety cabinet instead of through the sash opening.
  • Supply and exhaust blowers adapt to real-time conditions and correct airflow parameters.
  • Wireless sash-position systems proportionately adjust the fume hood’s blower speed to the sash height. An alarm sounds if the fume hood is not working properly. A screen mounted on the front of the hood displays alarm messages.
  • Temperature sensors inside fume hoods can detect unusual temperature increases caused by fire. The sensors set off alarms and can send an electronic message to the safety officer or site manager.